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264 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Where do cells get their energy to perform their many tasks
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from outside sources
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energy enters most ecosystems as
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sunlight and leaves as heat
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true or false: the chemical elements essential for life are recycled
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true
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What does photosynthesis generate
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oxygen and organic molecules that the mitochondria of eukaryotes (including plants and algae) use as fuel for cellular respiration
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Why do cells harvest chemical energy that is stored in organic molecules
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They use the energy to regenerate atp
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What is atp
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the molecule that drives most cellular work
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What are the 3 key pathways of respiration?
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glycolisis, the citric acid cycle, and oxidative phosphorylation
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What is fermentation?
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Is a simpler pathway coupled to glycolisis that has deep evolutionary roots
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What is the function of catabolic metabolic pathways
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release energy stored in complex organic molecules
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_____ _______ plays a major role in catabolic metabolic pathways
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electron transfer
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Why do organ compounds possess potential energy
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They possess potential energy as a result of the arrangement of electrons in the bonds between their atoms
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What is the function of enzymes
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They catalyze the systematic degradation of organic molecules that are rich in energy to simpler waste products that have less energy
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true or false: some of the released energy is used to work; the rest is dissipated as heat
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true
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one type of the catabolic process, _______, leads to the partial degradation of sugars without the use of oxygen
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fermentation
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a more efficient and widespread catabolic process,_______ ______, consumes oxygen as a reactant to complete the breakdown of a variety of organic molecules
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aerobic respiration
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some prokaryotes use compounds other than oxygen as reactants in similar process of aerobic respiration called
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anaerobic respiration
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although _______ ______ technically includes both aerobic and anaerobic processess, the term is commonly used to refer only to the ______ ______
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cellular respiration; aerobic process.
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______ _______ is similar in broad principle to the combustion of gasoline in an automobile engine after oxygen is mixed with hydrocarbon fuel.
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aerobic respiration
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true or false: food provides the fuel for respiration. the exhaust is carbon dioxide and water
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true
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What is the overall catabolic process
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organic compounds+ O2 à CO2+H2O+ energy (ATP +heat)
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carbohydrates, fats and proteins can all be used as fuel, but it is most useful to consider glucose which is
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C6H12O6+62 à 6CO2+6H2O+energy (ATP + heat)
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the catabolism of glucose is exergonic, with ...
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Dg=-686 kcal per mole of glucose
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catabolic pathways transfer the electrons stored in food molecules, releasing...
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energy that is used to synthesize atp.
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reactions that result in the transfer of one or more electrons (-e) from one reactant to another are...
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oxidation reduction reactions or 'redox reactions '
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the loss of electrons from a substance is called
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oxidation
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the addition of electrons to another substance is called
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reduction
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Why is adding electrons to a substance called reduction
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because negatively charged electrons added to an atom reduce the amount of positive charge of that atom
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the formation of table salt from sodium chloride, Na+Cl à Na+ Cl- ...is what type of reaction
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redox reaction
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how is ' Na + Cl à Na+Cl- 'a redox reaction
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sodium is oxidized and chlorine is reduced (it's charge drops from 0 to -1)
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What is a more general redox reduction
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-Xe + You +-Ye
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in -Xe + YàX +-Ye what is X
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the electron donor, is the reducing agent and reduces Y by donating an electron to it
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in -Xe + YàX +-Ye what is Y
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the electron recipient, is the oxidizing agent and oxidizes X by removing it's electron
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true or false: redox reactions require both a donor and an acceptor
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true
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What event do redox reactions also occur at
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when the transfer of electrons is not complete but involves a change in the degree of electron sharing in covalent bonds
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in the combustion of methane to form water and carbon dioxide, the non polar covalent bonds of methane (C-H) and oxygen (O=O) are converted to...
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polar covalent bonds (C=O and O-H)
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What happens when methane reacts with oxygen to form carbon dioxide
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the electrons end up farther away from the carbon atom and closer to their new covalent partners, the oxygen atom
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when methane reacts with oxygen to form carbon dioxide. in effect the carbon atom has been ...
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partially lost its shared electrons . thus methane has been oxidized
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what happens when oxygen reacts with the hydrogen from methane to form water
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the electrons of the covalent bonds are drawn closer to the oxygen
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in effect of oxygen reacting with the hydrogen from methane to form water what happens
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each oxygen atom has partially gained electrons, and so the oxygen molecule has been reduced
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true or false: oxygen is very electronegative and is one of the most potent of all oxidizing agents
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true
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_________ must be added to pull an electron away from an atom
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energy
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the more electronegative the atom...
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the more energy is required to take an electron away from it
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when does an electron lose potential
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when it shifts from a less electronegative atom toward a more electronegative one
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a redox reaction that relocates electrons closer to oxygen ....
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releases chemical energy that can do work
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give an example of a redox reaction that relocates electrons closer to oxygen
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the burning of methane
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when are organic fuel molecules oxidized?
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during cellular respiration
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What is respiration ?
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the oxidation of glucose and other molecules in food
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What type of process is respiration
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Is a redox process
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how is respiration a redox process
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. in a series of reactions, glucose is oxidized and oxygen is reduced .
.the electrons lose potential energy along the way, and energy is released |
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true or false: organic molecules that contain an abundance of hydrogen are excellent fuels
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true
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Why are organic molecules that contain an abundance of hydrogen excellent fuels
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.the bonds of these organic molecules are a source of 'hilltop' electrons, whose energy may be released as the electrons 'fall' down an energy gradient when they are transferred to oxygen
. as hydrogen is transferred from glucose to oxygen the energy state of the electron changes |
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true or false: in respiration, the oxidation of glucose transfers electrons to a lower energy state.
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true
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What are carbohydrates and fats
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They are the main energy - yielding foods. are reservoirs of electrons associated with hydrogen.
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molecules of carbohydrates and fats are stable because
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of the barrier of activation energy
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without the barrier of activation energy , what would happen to a food molecule
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like glucose would combine almost instantaneously with O2
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What happens if the activation energy is supplied by igniting glucose
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it burns in air to release 686 kcal (2,870 kJ) of heat per mole of glucose (about 180 g)
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What reaction can not happen at body temperatures
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activation energy is supplied by igniting glucose
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true or false: the "fall" of electrons during respiration is steowise, via NAD+ and an electron transport chain
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true
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______ _______ does not oxidize glucose in a single step that transfers all the hydrogen in the fuel to oxygen at one time
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cellular respiration
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true or false: cellular respiration does not oxidize glucose in a single step but rather glucose and other fuels are broken down in a series of steps each catalyzed by a specific enzyme
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true
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at key steps of oxidizing glucose....
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electrons are stripped from glucose
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in many oxidation reactions ....
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the electron is transferred with a proton, as a hydrogen atom
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how are the hydrogen atoms transferred?
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the hydrogen atoms are not transferred directly to oxygen but are passed first to a coenzyme called NAD+ ( nicotinamide adenine di nucleotide)
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Why is NAD+ a well suited electron carrier ?
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because it can cycle easily between oxidized (NAD+) and reduced (NADH) states
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What are the functions of NAD+ as an electron acceptor
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it is an oxidizing agent during respiration
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how does NAD+ trap electrons from glucose
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.dehydrogenase enzymes strip two hydrogen atoms from the substrate (glucose), thus oxidizing it
. the enzyme passes two electrons and one proton to NAD+ .the other proton is released as H+ to the surrounding solution |
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What happens when NAD+ receives two electrons and only 1 proton?
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it has its charge neutralized when it is reduced to NADH
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true or false: NAD+ functions as the oxidizing agent in many of the redox steps during the breakdown of glucose
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true
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What happens to the electrons carried by NADH
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lose very little of their potential energy in this process
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each NADH molecule formed during respiration represents .... which is .....
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stored energy. this energy is tapped to synthesize ATP as electrons ' fall' down an energy gradient from NADH to oxygen
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How are electrons extracted from glucose and stored in NADH finally transferred to oxygen ?
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Unlike Unlike the explosive release of heat energy that occurs when H2 and O2 are combined (with a spark for activation energy), cellular respiration uses an electron transport chain to break the fall of electrons to O2 into several energy-releasing steps.
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How are electrons extracted from glucose and stored in NADH finally transferred to oxygen ?
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Unlike Unlike the explosive release of heat energy that occurs when H2 and O2 are combined (with a spark for activation energy), cellular respiration uses an electron transport chain to break the fall of electrons to O2 into several energy-releasing steps.
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How are electrons extracted from glucose and stored in NADH finally transferred to oxygen ?
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Unlike the explosive release of heat energy that occurs when H2 and O2 are combined (with a spark for activation energy), cellular respiration uses an electron transport chain to break the fall of electrons to O2 into several energy-releasing steps.
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What does the electron chain consist of ?
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several molecules (primarily proteins) built into the inner membrane of mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.
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In the electron transport chain, electrons released from food
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are shuttled by NADH to the “top” higher-energy end of the chain.
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In the electron transport chain, electrons released from food
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are shuttled by NADH to the “top” higher-energy end of the chain.
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At the 'bottom' lower energy end of the electron transfer chain ....
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oxygen captures the electrons along with H+ to form water.
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Electron transfer from NADH to oxygen is an...
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exergonic reaction with a free-energy change of −53 kcal/mol.
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Electrons are passed to increasingly electronegative molecules in the chain until ....
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they reduce oxygen, the most electronegative receptor.
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Electrons are passed to increasingly electronegative molecules in the chain until ....
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they reduce oxygen, the most electronegative receptor.
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True or false: • Each “downhill” carrier is more electronegative than, and thus capable of oxidizing, its “uphill” neighbor, with oxygen at the bottom of the chain.
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True
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The electrons removed from glucose by NAD+ ....
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fall down an energy gradient in the electron transport chain to a far more stable location in the electronegative oxygen atom.
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True or false: In summary, during cellular respiration, most electrons travel the following “downhill” route: glucose à NADH à electron transport chain à oxygen.
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True
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Respiration occurs in three metabolic stages. What are they?
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glycolysis, the citric acid cycle, and the electron transport chain and oxidative phosphorylation.
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Glycolysis is included in the metabolic stages because
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most respiring cells deriving energy from glucose use glycolysis to produce starting material for the citric acid cycle.
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Where does glycolysis occur and what is its function?
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Glycolysis occurs in the cytosol. It begins catabolism by breaking glucose into two molecules of pyruvate.
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• In eukaryotes, pyruvate enters the mitochondrion and is oxidized to a compound called acetyl CoA, which enters the ...
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Citric acid cycle
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True or false: • Several steps in glycolysis and the citric acid cycle are redox reactions in which dehydrogenase enzymes transfer electrons from substrates to NAD+, forming NADH.
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True
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True or false: • Several steps in glycolysis and the citric acid cycle are redox reactions in which dehydrogenase enzymes transfer electrons from substrates to NAD+, forming NADH.
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True
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What happens in the third stage of respiration ?
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• In the third stage of respiration, the electron transport chain accepts electrons from the breakdown products of the first two stages (most often via NADH).
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True or false: • Several steps in glycolysis and the citric acid cycle are redox reactions in which dehydrogenase enzymes transfer electrons from substrates to NAD+, forming NADH.
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True
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What happens in the third stage of respiration ?
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• In the third stage of respiration, the electron transport chain accepts electrons from the breakdown products of the first two stages (most often via NADH).
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True of false:In the electron transport chain, the electrons move from molecule to molecule until they combine with molecular oxygen and hydrogen ions to form water.
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True
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As the electrons are passed along the chain, the energy released at each step in the chain is stored in ....
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a form the mitochondrion (or prokaryotic cell) can use to make ATP.
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As the electrons are passed along the chain, the energy released at each step in the chain is stored in ....
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a form the mitochondrion (or prokaryotic cell) can use to make ATP.
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Why is mode of ATP synthesis is called oxidative phosphorylation
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T
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Why is oxidative phosphorylation a type of mode of ATP synthesis?
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T
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Why is oxidative phosphorylation a type of mode of ATP synthesis?
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2
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Why is oxidative phosphorylation a type of mode of ATP synthesis?
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because it is powered by the redox reactions of the electron transport chain.
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In eukaryotic cells, the inner membrane of the mitochondrion is...
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the site of electron transport and chemiosmosis, the processes that together constitute oxidative phosphorylation.
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In eukaryotic cells, the inner membrane of the mitochondrion is...
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the site of electron transport and chemiosmosis, the processes that together constitute oxidative phosphorylation.
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In prokaryotes, the site of electron transport and chemiosmosis, the processes that together constitute oxidative phosphorylation is....
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The plasma membrane
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True or false: Oxidative phosphorylation produces almost 90% of the ATP generated by respiration.
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True
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• Some ATP is also formed directly during glycolysis and the citric acid cycle by ______-______ ______in which an enzyme transfers a phosphate group from an organic substrate molecule to ADP, forming ATP.
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substrate-level phosphorylation,
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What happens when each molecule of glucose degraded to carbon dioxide and water by respiration
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the cell makes up to 36 to 38 ATP, each with 7.3 kcal/mol of free energy.
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What happens when each molecule of glucose degraded to carbon dioxide and water by respiration
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the cell makes up to 36 to 38 ATP, each with 7.3 kcal/mol of free energy.
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True or false: Respiration uses the small steps in the respiratory pathway to break the large denomination of energy contained in glucose into the small change of ATP.
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True
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True or false: The quantity of energy in ATP is more appropriate for the energy level of work required in the cell.
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True
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During glycolysis ...
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glucose, a six-carbon sugar, is split into two three-carbon sugars.
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When glucose is split into two 3 carbon sugars. These smaller sugars are then...
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oxidized and rearranged to form two molecules of pyruvate, the ionized form of pyruvic acid.
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During glycolysis ....
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glucose, a six-carbon sugar, is split into two three-carbon sugars.
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During glycolysis ....
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glucose, a six-carbon sugar, is split into two three-carbon sugars.
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Each of the ten steps of glycolysis is catalyzed by a
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Specific enzyme
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During glycolysis ....
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glucose, a six-carbon sugar, is split into two three-carbon sugars.
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Each of the ten steps of glycolysis is catalyzed by a
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Specific enzyme
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The steps of glycolysis can be divided into two phases. What are they ?
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1. Energy investment phase
2. The energy pay off phase |
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What is the function of the energy investment phase
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The cell spends ATP
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What is the function of the energy payoff phase?
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The investment of the spent ATP from the first phase is repaid with interest.
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What is the net yield from glycolysis ?
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is 2 ATP and 2 NADH per glucose.
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True or false: no carbon is released as CO2 during glycolysis
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True
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True or false: Glycolysis can occur whether or not O2 is present.
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True
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True or false: o No carbon is released as CO2 during glycolysis.
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True
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True or false: No carbon is released as CO2 during glycolysis.
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True
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True or false: No carbon is released as CO2 during glycolysis.
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True
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What happens if O2 is present?
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the chemical energy stored in pyruvate and NADH can be extracted by pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation.
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True or false: More than three-quarters of the original energy in glucose is still present in the two molecules of pyruvate.
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True
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What happens if molecular oxygen is present in eukaryotic cells
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pyruvate enters the mitochondrion, where enzymes of the citric acid cycle complete the oxidation of the organic fuel to carbon dioxide.
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What happens if molecular oxygen is present in eukaryotic cells
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pyruvate enters the mitochondrion, where enzymes of the citric acid cycle complete the oxidation of the organic fuel to carbon dioxide.
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What happens if molecular oxygen is present in prokaryotic cells ?
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Pyruvate enters the cytosol where enzymes of the citric acid cycle complete the oxidation of the organic fuel to carbon dioxide.
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What happens if molecular oxygen is present in eukaryotic cells
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pyruvate enters the mitochondrion, where enzymes of the citric acid cycle complete the oxidation of the organic fuel to carbon dioxide.
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What happens if molecular oxygen is present in prokaryotic cells ?
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Pyruvate enters the cytosol where enzymes of the citric acid cycle complete the oxidation of the organic fuel to carbon dioxide.
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What happens After pyruvate enters the mitochondrion via active transport,
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it is converted to a compound called acetyl coenzyme A, or acetyl CoA.
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• The step, linking glycolysis and the citric acid cycle, is carried out by a multienzyme complex that catalyzes three reactions. What are they?
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1. A carboxyl group is removed as CO2. The carbon dioxide is fully oxidized and thus has little chemical energy.
2. The remaining two-carbon fragment is oxidized to form acetate. An enzyme transfers the pair of electrons to NAD+ to form NADH. 3. Acetate combines with coenzyme A to form the very reactive molecule acetyl CoA. |
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True or false: • Due to the chemical nature of the CoA group, a sulfur-containing compound derived from a B vitamin, acetyl CoA has a high potential energy.
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True
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The reaction of acetyl CoA to yield lower-energy products is
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Highly exergonic
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True or false: The citric acid cycle oxidizes organic fuel derived from pyruvate.
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True
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True or false: Three CO2 molecules are released, including the one released during the conversion of pyruvate to acetyl CoA.
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True
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The citric acid cycle generates one ATP per turn by
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substrate-level phosphorylation.
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Most of the chemical energy is transferred to
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NAD+ and a related electron carrier, the coenzyme FAD, during the redox reactions.
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transfer high-energy electrons to the electron transport chain.
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The reduced coenzymes, NADH and FADH
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transfer high-energy electrons to the electron transport chain.
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The reduced coenzymes, NADH and FADH
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True or false: • The citric acid cycle has eight steps, each catalyzed by a specific enzyme.
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True
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• The citric acid cycle has eight steps, each catalyzed by a specific enzyme.
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combining with the compound oxaloacetate, forming citrate.
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The acetyl group of acetyl CoA joins the citric acid cycle by
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combining with the compound oxaloacetate, forming citrate.
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What is the function of the next seven steps of the citric acid cycle
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The next seven steps decompose the citrate back to oxaloacetate.
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What is the function of NADH and FADH2
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These reduced coenzymes link glycolysis and the citric acid cycle to oxidative phosphorylation, which uses energy released by the electron transport chain to power ATP synthesis.
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True or false: The inner mitochondrial membrane couples electron transport to ATP synthesis.
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True
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What is the electron transport chain in a eukaryotic cell?
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is a collection of molecules embedded in the cristae, the folded inner membrane of the mitochondrion.
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Where is the electron transport chain in a prokaryotic cell located ?
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In the plasma membrane
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The folding of the inner membrane to form cristae increases ....
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its surface area, providing space for thousands of copies of the chain in each mitochondrion.
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What are most of the components of an electron transport chain?
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are proteins that exist in multiprotein complexes numbered I– IV.
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Tightly bound to the proteins of the electron transport chain are
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prosthetic groups, nonprotein components essential for catalysis.
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What happens to electrons as they pass down the electron transport chain ?
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Drop in free energy
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True or false: During electron transport along the chain, electron carriers alternate between reduced and oxidized states as they accept and donate electrons.
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True
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When does each component of the electron transport chain become reduced ?
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when it accepts electrons from its “uphill” neighbor, which is less electronegative.
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True or false: It is the regeneration of oxaloacetate that makes this process a cycle.
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True
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After each component of the electron transport chain becomes reduced what happens?
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It then returns to its oxidized form as it passes electrons to its more electronegative “downhill” neighbor.
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Electrons carried by NADH are transferred to
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the first molecule in the electron transport chain, a flavoprotein.
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WHat happens after electrons are transferred to a flavoprotein
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In the next redox reaction, the flavoprotein returns to its oxidized form as it passes electrons to an iron-sulfur protein.
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After electrons are transferred to a flavoprotein and then passed to a iron-sulfur protein what happens?
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The iron-sulfur protein then passes the electrons to a compound called ubiquinone, a small hydrophobic molecule and the only member of the electron transport chain that is not a protein.
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True or false: Ubiquinone is individually mobile within the membrane rather than residing in a particular complex.
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True
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Most of the remaining electron carriers between ubiquinone and oxygen are proteins called ....
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Cytochromes
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What is the prosthetic group of each cytochromes?
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is a heme group with an iron atom that accepts and donates electrons.
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What is the last cytochrome of the electron transport chain and what is its function?
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cyt a3, passes its electrons to oxygen, which is very electronegative.
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The electrons carried by FADH 2 ....
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have lower free energy and are added at a lower energy level than those carried by NADH.
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True or false: o The electron transport chain provides about one-third less energy for ATP synthesis when the electron donor is FADH2 rather than NADH.
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True
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For each acetyl group that enters the citric acid phase ...
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3 NAD+ are reduced to NADH.
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True or False: The electron transport chain generates no ATP directly.
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True
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What is the function of the electron transport chain?
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Its function is to break the large free-energy drop from food to oxygen into a series of smaller steps that release energy in manageable amounts.
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True or false: In one step, electrons are transferred to FAD instead of NAD+. FAD then accepts 2 electrons and 2 protons to become FADH2.
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True
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In the cells of plants, bacteria, and some animal tissues, the citric acid cycle forms ....
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an ATP molecule by substrate-level phosphorylation.
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In many animal cells how is guanosine triphosphate (GTP) formed ?
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by the same process of substrate-level phosphorylation.
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How may guanosine triphosphat (GTP) be used?
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guanosine triphosphat (GTP) may be used to synthesize ATP or directly power work in the cell.
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Most of the ATP produced by respiration results from
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oxidative phosphorylation, when the NADH and FADH2 produced by the citric acid cycle relay the electrons extracted from food to the electron transport chain.
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This process supplies the necessary energy for the phosphorylation of ADP to ATP.
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True or false: Only 4 of 38 ATP produced by the respiration of glucose are produced by substrate-level phosphorylation: 2 net ATP from glycolysis and 2 ATP from the citric acid cycle.
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True
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_______ and ______ account for most of the energy extracted from glucose.
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NADH and FADH2
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True or false: Chemiosmosis couples electron transport and energy release to ATP synthesis.
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True
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• A protein complex in the cristae, ATP synthase, actually makes ATP from ADP and inorganic phosphate.
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True
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What protein complex in the cristae actually makes ATP from adp and inorganic phosphate ?
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ATP synthase
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What works like an ion pump working in reverse
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ATP synthesis
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Ion pumps usually use ATP as an energy source to transport ions against their gradients.
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Enzymes can catalyze a reaction in either direction, depending on the _______ for the reaction, which is affected by the local concentrations of reactants and products.
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Dg
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Rather than hydrolyzing ATP to pump protons against their concentration gradient, under the conditions of cellular respiration, ATP synthase uses ....
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the energy of an existing ion gradient to power ATP synthesis.
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Rather than hydrolyzing ATP to pump protons against their concentration gradient, under the conditions of cellular respiration, ATP synthase uses ....
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the energy of an existing ion gradient to power ATP synthesis.
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What is the power source for ATP synthase
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is a difference in the concentrations of H+ on opposite sides of the inner mitochondrial membrane.
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• This process, in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP, is called
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Chemiosmosis
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the process, in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP, is called
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Chemiosmosis
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Here, osmosis refers to the flow of H+ across a membrane.
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What is the aTP synthase?
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is a multisubunit complex with four main parts, each made up of multiple polypeptides.
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Protons move one by one into binding sites on one of the parts of the ATP synthase (the rotor), causing it to
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spin in a way that catalyzes ATP production from ADP and inorganic phosphate.
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ATP synthase is the smallest molecular rotary motor known in nature.
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Protons move one by one into binding sites on one of the parts of the ATP synthase (the rotor), causing it to
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spin in a way that catalyzes ATP production from ADP and inorganic phosphate.
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ATP synthase is the smallest molecular rotary motor known in nature.
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How does the inner mitochondrial membrane or the prokaryotic plasma membrane generate and maintain the H+ gradient that drives ATP synthesis in the ATP synthase protein complex?
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. Establishing the H+ gradient is the function of the electron transport chain.
o The chain is an energy converter that uses the exergonic flow of electrons to pump H+ across the membrane from the mitochondrial matrix into the intermembrane space. o The H+ has a tendency to diffuse down its gradient. |
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What type of molecules are the only place where H+ can diffuse back to the matrix
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ATP synthase molecules
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What type of molecules are the only place where H+ can diffuse back to the matrix
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ATP synthase molecules
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The exergonic flow of H+ is used by the enzyme to generate ATP. This coupling of the redox reactions of the electron transport chain to ATP synthesis is an example of
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Chemiosmosis
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What type of molecules are the only place where H+ can diffuse back to the matrix
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ATP synthase molecules
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The exergonic flow of H+ is used by the enzyme to generate ATP. This coupling of the redox reactions of the electron transport chain to ATP synthesis is an example of
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Chemiosmosis
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How does the electron transport chain pump protons?
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o Certain members of the electron transport chain accept and release H+ along with electrons.
o At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. o The electron carriers are spatially arranged in the membrane in such a way that protons are accepted from the mitochondrial matrix and deposited in the intermembrane space. |
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What type of molecules are the only place where H+ can diffuse back to the matrix
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ATP synthase molecules
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The exergonic flow of H+ is used by the enzyme to generate ATP. This coupling of the redox reactions of the electron transport chain to ATP synthesis is an example of
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Chemiosmosis
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How does the electron transport chain pump protons?
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o Certain members of the electron transport chain accept and release H+ along with electrons.
o At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. o The electron carriers are spatially arranged in the membrane in such a way that protons are accepted from the mitochondrial matrix and deposited in the intermembrane space. |
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The H+ gradient that results is the
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proton-motive force,
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What type of molecules are the only place where H+ can diffuse back to the matrix
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ATP synthase molecules
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The exergonic flow of H+ is used by the enzyme to generate ATP. This coupling of the redox reactions of the electron transport chain to ATP synthesis is an example of
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Chemiosmosis
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How does the electron transport chain pump protons?
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o Certain members of the electron transport chain accept and release H+ along with electrons.
o At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. o The electron carriers are spatially arranged in the membrane in such a way that protons are accepted from the mitochondrial matrix and deposited in the intermembrane space. |
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The H+ gradient that results is the
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proton-motive force,
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What is the proton motive force
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a gradient with the capacity to do work.
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What is the function of the proton-motive force
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o The force drives H+ back across the membrane through the specific H+ channels provided by ATP synthases.
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What is chemiosmosis?
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• Chemiosmosis is an energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work.
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What is chemiosmosis?
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• Chemiosmosis is an energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work.
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In mitochondria, the energy for proton gradient formation comes from
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exergonic redox reactions, and ATP synthesis is the work performed.
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Chemiosmosis in chloroplasts also generates ATP, but
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light drives both the electron flow down an electron transport chain and the resulting H+ gradient formation.
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Prokaryotes generate H+ gradients across their
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Plasma membrane
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Prokaryotes use the proton-motive force not only to generate ATP but also to
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pump nutrients and waste products across the membrane and to rotate their flagella.
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True or false: During cellular respiration, most energy flows as follows: glucose à NADH à electron transport chain à proton-motive force à ATP.
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True
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What are the products generated when cellular respiration oxidizes a molecule of glucose to six molecules of CO2?
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o Four ATP molecules are produced by substrate-level phosphorylation during glycolysis and the citric acid cycle.
o Many more ATP molecules are generated by oxidative phosphorylation. o Each NADH from the citric acid cycle and the conversion of pyruvate contributes enough energy to the proton-motive force to generate a maximum of 3 ATP. |
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What are are three reasons we cannot state an exact number of ATP molecules generated by one molecule of glucose.
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1. Phosphorylation and the redox reactions are not directly coupled to each other, so the ratio of the number of NADH to the number of ATP is not a whole number
2. The ATP yield varies slightly depending on the type of shuttle used to transport electrons from the cytosol into the mitochondrion. 3. The proton-motive force generated by the redox reactions of respiration may drive other kinds of work, such as mitochondrial uptake of pyruvate from the cytosol. |
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What are are three reasons we cannot state an exact number of ATP molecules generated by one molecule of glucose.
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1. Phosphorylation and the redox reactions are not directly coupled to each other, so the ratio of the number of NADH to the number of ATP is not a whole number
2. The ATP yield varies slightly depending on the type of shuttle used to transport electrons from the cytosol into the mitochondrion. 3. The proton-motive force generated by the redox reactions of respiration may drive other kinds of work, such as mitochondrial uptake of pyruvate from the cytosol. |
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True or false: The mitochondrial inner membrane is impermeable to NADH, so NADH produced in glycolysis must be conveyed into the mitochondrion by one of several electron shuttle systems.
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True
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True or false: Depending on the kind of shuttle in a particular cell type, the electrons are passed either to NAD+ or to FAD in the mitochondrial matrix.
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True
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True or false: o If the electrons are passed to FAD, as in brain cells, 2 ATP result from each NADH that was originally generated in the cytosol.
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True
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True or false: o If the electrons are passed to mitochondrial NAD+, as in liver cells and heart cells, the yield is about 3 ATP per NADH.
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True
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True or false: o If the electrons are passed to mitochondrial NAD+, as in liver cells and heart cells, the yield is about 3 ATP per NADH.
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True
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all the proton-motive force generated by the electron transport chain were used to drive ATP synthesis, one glucose molecule could ....
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generate a maximum of 28 ATP produced by oxidative phosphorylation plus 4 ATP (net) from substrate-level phosphorylation to give a total yield of about 32 ATP (or only about 30 ATP if the less efficient shuttle were functioning).
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Dr koo said 36 or 38
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• How efficient is respiration in generating ATP?
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.Efficiency of respiration is 7.3 kcal/mol times 32 ATP/glucose divided by 686 kcal/mol glucose, which equals 0.34, or 34%.
.the actual percentage may be higher because Dg is lower under cellular conditions |
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Without electronegative oxygen to pull electrons down the transport chain.... What happens?
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oxidative phosphorylation eventually ceases.
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True or false: In alcohol fermentation, pyruvate is converted to ethanol in two steps.
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True
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How is pyruvate converted to ethanol ?
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o Pyruvate is converted to a two-carbon compound, acetaldehyde, by the removal of CO2.
o Acetaldehyde is reduced by NADH to ethanol. This process regenerates the supply of NAD+ needed for the continuation of glycolysis. |
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True or false: Alcohol fermentation by yeast is used in brewing, baking, and winemaking.
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True
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During lactic acid fermentation...
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pyruvate is reduced directly by NADH to form lactate (the ionized form of lactic acid) without the release of CO2.
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True or false: o Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.
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True
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Why do Human muscle cells switch from aerobic respiration to lactic acid fermentation
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to generate ATP when O2 is scarce.
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This may occur in the early stages of strenuous exercise.
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Fermentation, anaerobic respiration, and aerobic respiration are ...
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three alternative cellular pathways for producing ATP from sugars.
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Why does fermentation, anaerobic respiration and aerobic respiration use glycolysis ?
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to oxidize sugars to pyruvate with a net production of 2 ATP by substrate-level phosphorylation.
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In fermentation, anaerobic respiration, and aerobic respiration NAD+ is...
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the oxidizing agent that accepts electrons from food during glycolysis.
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In fermentation, anaerobic and aerobic respiration a key difference is ...
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the mechanisms for oxidizing NADH to NAD+, which is required to sustain glycolysis.
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Most cellular respiration requires ____ to produce ATP
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O2 (oxygen)
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In fermentation, the final electron acceptor is
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an organic molecule such as pyruvate (lactic acid fermentation) or acetaldehyde (alcohol fermentation).
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In cellular respiration, electrons carried by NADH are transferred to
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an electron transport chain and move stepwise down a series of redox reactions to a final electron acceptor.
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In aerobic respiration, the final electron acceptor is
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Oxygen
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in anaerobic respiration, the final acceptor is
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another molecule that is less electronegative than oxygen.
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Transfer of electrons from NADH to the electron transport chain not only regenerates the NAD+ required for glycolysis but
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also pays an ATP bonus when the stepwise electron transport from this NADH to oxygen drives oxidative phosphorylation.
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More ATP is produced by
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the oxidation of pyruvate in the mitochondrion, which is unique to respiration.
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Without an electron transport chain...
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the energy still stored in pyruvate is unavailable to most cells.
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True or false: cellular respiration harvests much more energy from each sugar molecule than fermentation can.
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True
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Aerobic respiration yields up to 16 times as much ATP per glucose molecule as does fermentation—up to 46 or 38 molecules of ATP for respiration, compared with 2 molecules of ATP produced by substrate-level phosphorylation in fermentation.
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True
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______ _____carry out only fermentation or anaerobic respiration and cannot survive in the presence of oxygen
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Obligate anaerobes
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However, there are two general mechanisms by which certain cells can oxidize organic fuel and generate ATP without the use of oxygen....what are they?
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Fermentation and anaerobic respiration
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Yeast and many bacteria are _____ _____ that can survive using either fermentation or respiration
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Facultative anaerobes
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For facultative anaerobes, pyruvate is
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a fork in the metabolic road that leads to two alternative catabolic routes.
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Glycolysis and the citric acid cycle are
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major intersections of various catabolic and anabolic (biosynthetic) pathways.
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What are the two major fuels for resiration
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Proteins and fats
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True or false: Proteins must first be digested to individual amino acids.
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True
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Many of the amino acids are used by
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the organism to build new proteins
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Amino acids that will be catabolized must have their amino groups removed via
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Deamination
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Catabolism can also harvest energy stored in fats obtained from
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food or from storage cells in the body.
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After fats are digested to glycerol and fatty acids, glycerol can be converted to
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glyceraldehyde-3-phosphate, an intermediate of glycolysis.
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The rich energy of fatty acids is accessed as fatty acids are split into two-carbon fragments via
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Beta oxidation
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These molecules enter the citric acid cycle as acetyl CoA.
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Anaerobic respiration takes place in organisms that have an electron transport chain but ...
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do not use oxygen as a final electron acceptor at the end of the chain.
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Some “sulfate-reducing” marine bacteria, for instance, use the electronegative sulfate ion (SO 42-) at the end of their respiratory chain.
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True or false: • A gram of fat oxidized by respiration generates twice as much ATP as a gram of carbohydrate.
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True
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Fermentation provides...
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a mechanism by which some cells can oxidize organic fuel and generate ATP without the use of oxygen or any electron transport chain (that is, without cellular respiration).
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True or false: If oxygen is present, additional ATP can be generated when NADH delivers its electrons to the electron transport chain.
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True
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Fermentation allows generation of ATP from glucose by
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substrate-level phosphorylation.
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Under aerobic conditions, NADH transfers....
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its electrons to the electron transfer chain, recycling NAD+.
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What does fermentation consist of ?
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Glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis
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Fermentation pathways recycle NAD+ by
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transferring electrons from NADH to pyruvate or derivatives of pyruvate.
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