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66 Cards in this Set
- Front
- Back
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How do cells obtain energy from food? |
Get it from chemical bond energy stored in "food" - energy is store and transported to activated carrier molecules |
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Whats the most important food source for obtaining energy? |
Carbohydrates (sugars) |
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Activated carrier molecules |
-Molecules that store energy generated from oxidation of food molecules - contain one or more high energy content - provide energy for biosynthetic reactions |
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Examples of ACM used in metabolism |
ATP, NADH, NADPH, FADH2 |
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What group is carried in ATP |
Phosphate |
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What group is carried in NADH, NADPH, FADH2 |
Electrons and hydrogens |
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What group is carried in acetyl coA |
Acetyl group |
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What are electron carriers? |
Coenzymes that carry electrons from one reaction to another - readily accept a hydride atom (H, 2 electrons and a proton) and donate it -vital in the production of energy during the oxidation of glucose |
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Examples of electron carriers |
Nad+, nadp+, fad |
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What are redox reactions? |
Reaction that involves the loss or gain of an electron -always coupled |
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Lose electron |
Oxidation (LEO) |
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Gain electron |
Reduction (GER) |
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Redox of nad+ |
-High energy molecule binds to an enzyme, gives up H (oxidized) -NAD+ accepts H (reduced) - carries electrons to electron transport chain |
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Catabolism |
Breakdown of complex molecules into simpler ones |
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Anabolism |
Synthesizes simple molecules into more complex ones (opposite process to catabolism) |
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Similarities between Catabolism of glucose and cellular respiration |
- Reactants and products are the same - energy is released by converting glucose to co2 - total energy release is same |
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Differences between Catabolism of glucose and cellular respiration |
- when burning glucose, energy is released as heat - cells cant use heat, must harvest in tiny and tightly controlled steps so that most energy us stored as atp |
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Harvesting energy from glucose catabolism |
Atp and activated molecules like nadh provides energy currency for cells to do work |
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Ways to make atp |
1. Substrate level phosphorylation 2. Oxidative Phosphorylation 3. Photophosphorylation |
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Substrate level phosphorylation |
Generated few atp during glycolisis |
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Oxidative phosphorylation |
Electrons produced from organic fuel molecules in redox reactions used to pump H+ across a membrane (proton pump) - protons are then allowed to back across and run atp synthase |
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Photophosphorylation |
Occurs in chloroplasts (autotrophs) Cyclic and non cyclic phosphorylation |
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Three stages fir extracting energy from food |
1. Digestion - takes place outside of cells (intestine) or in lysosome 2. Glycolysis - occurs in cytoplasm 3. TCA and Oxidative phosphorylation - occurs in mitochondria |
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Stage 1 |
Digestive enzymes hydrolyze macromolecules into their monomeric subunits Eg proteins to amino acids Small organic molecules make their way to cytosol - oxidation process for generating atp begins |
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Cellular Respiration OVERALL |
- energy produced during each step through oxidation of glucose. Transferring electrons from molecule to molecule - some energy is lost each time electrons move, with the energy being captured by either ATP or by making reducing energy carriers like NADH/FADH2 - The depleted electrons are then transferred to the final electron acceptop, where oxidized carriers (NAD+/FAD) are regenerated, allowing the cycle to continue. - oxygen - aerobic respiration - other organic molecules - fermentation |
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Highlights of glycolysis |
- 2 ATPs spent to make glucose more reactive - phosphorylated sugar is split - each 3-carbon sugar joins with a free phosphate, sugar becomes more reactive - lastly the 2 phosphates in each sugar is transferred to ATP - produce 2 pyrucates per glucose |
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Mitochondrial structures |
- matrix - Inner membrane - outer membrane - intermembrane space |
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matrix (mitochondria) |
contains a highly concentrated mixture of enzymes. -the enzymes are required for the oxidation of pyruvate and fatty acids and for the cytric acid cycle |
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Inner membrane (mitochondria) |
Folded into many cristae - the inner membrane consists of proteins that carry out oxidation reactions of E.T chain and ATP synthase that makes ATP in the matrix |
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Outer membrane (mitochondria) |
- contains a large channel forming protein called porin - is permeable to all molecules 5000 daltons or less |
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Intermembrane space(mitochondria) |
- contains several enzymes that use the ATP passing out the matrix to phosphorylate other nucleotides |
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Prepping pyruvate for the TCA cycle |
1. decarboxylationreaction: taking off a carbon 2.reducing (loading) NAD+ 3. ‘activating’ 2-carbon acyl groups pyruvate + NAD+ + CoA ---> acetyl-CoA + NADH + CO2 - catalyzed by pyruvate dehydrogenase enzyme complex |
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What is coenzyme A? |
- a nucleotide derivative - an organophosphate - a thiol - a coenzyme - thiol group reacts with carboxylic acids - ‘carries‘ acyl groups |
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What does the TCA cycle accomplish? |
- 2 carbon acyl unit is fully oxidized to yield two molecules of CO2 (two carbons of glucose fully oxidized), 1 GTP --> 1 ATP (substrate level phosphorylation), and reduced (activated) electron carrier: 3 NADH, 1 FADH2 - molecules required to restart the cycle is regenerated - need two turns for each molecule of glucose |
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How is energy generated in mitochondria |
by fully oxidixing glucose to CO2 in TCA cycle and glycolysis |
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How is ATP generated? |
Unleashing the electrons in NADH and FADH2 allows the mitochondria to generate most of the ATP for cellular function |
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What happens to reduced energy carriers? |
- loaded energy carriers (NADH and FADH2) carry their electrons to the matrix side of the inner mitochondrial membrane - they transfer electrons to the electron transport chain |
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What is the electron transport chain? |
- series of molecules embedded in inner mitochondrial membrane - NADH delivers electrons to top of the chain, oxygen catches them at the bottom of the chain - oxygen then joins hydrogen to form water |
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What is the output of ETC? |
- for every two electron carriers (4 electrons), one O2 molecule is reduced to two water molecules. - energy is released through movement of electrons in redox reactions used to generate proton gradient across the inner mitochondrial membrane |
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Components of ETC |
- molecules are arranged from low to high electronegativity, therefore electrons are held tighter the further they pass down the chain - the ultimate electron acceptor is oxygen, therefore all electrons in original glucose can be accounted for |
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How is ATP generated in the ETC? |
- by a process known as chemiosmosis |
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What is chemiosmosis? |
- harnessing the electrochemical gradient of H+ ions across a membrane to make ATP |
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What is proton motive force? |
- it is in mitochondria, chloroplasts, and many bacteria. - promotes movement of protons across membranes downhill the electrochemical potential - stores energy through a combination of voltage and proton gradients across the membrane - usually generated by ETC acting as a proton pump |
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What is the chemiosmotic theory? |
most ATP synthesis in respiring cells comes from the electrochemical gradient across inner mitochondrial membranes, generated using energy from NADH, FADH2, derived from breakdown of fuel molecules |
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ATP synthase |
Together membrane potential (ΔV) and pH gradient (ΔpH) form the proton motive that is used by ATP synthase to generate ATP |
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What is the actual energy yield from aerobic respiration? |
- 30 ATP per glucose - 1.5 ATP per FADH2 - 2.5 ATP per NADH |
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How efficient is is respiration in capturing the energy of glucose? |
- complete oxidation of glucose releases 686 kcal per mole - energy stored in each ATP: 7.3 kcal/mole - so energy captured: 30 ATP x 7.3 kcal/mole = 219 kcal/mole efficiency = (energy captured/energy released) x 100 = (219/686) x 100 = 32% |
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What happens if there is no oxygen in ETC? |
- oxidative phosphorylation backs up - buildup of loaded energy carriers waiting to be processed – all NADH, FADH2 in reduced form, therefore TCA cycle shuts down - if O. phosphorylation cannot operate, major source of ATP shut down - cells must rely on glycolysis - only 2 ATP (net) per glucose only organisms with low energy needs can cope |
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Coping with an anaerobic lifestyle |
organism / cell must find another way to ‘unload’ NADH(regenerate NAD+) |
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Fermentation |
- pyruvate or its derivative accepts electrons from NADH •converts NADH back to NAD+ and allows glycolysis to continue to produce ATP via substrate-level phosphorylation organic molecule + NADH --> reduced organic molecule + NAD+ |
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what are the two types of fermentation? |
1. lactid acid fermentation 2. alcoholic fermentation |
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- anaerobic respiration compared to aerobic respiration |
- extremely inefficient compared with aerobic respiration - just two ATP molecules per glucose molecule, compared with ~30 ATP in cellular respiration |
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Aerobic respiration vs fermentation |
- some organisms can survive using either fermentation or respiration eg. ‘facultative’ anaerobes such as yeast and many bacteria - at a cellular level in animals, some cells can behave as facultative anaerobes, some can’t eg. muscle cells (can) vs neurons (can't) |
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How are aerobic respirations vs fermentation similar? |
s |
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How are aerobic respirations vs fermentation different? |
s |
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what are the relative energy yields? |
s |
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Where do the acyl groups come from to form acetyl CoA? |
•oxidation of pyruvate (from carbohydrate) •breakdown of proteins •breakdown of fats, other lipids |
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What can the cell do with acetyl CoA? |
•oxidize it to make ATP (TCA cycle cellular respiration) •fat synthesis |
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Which process predominates? |
–lots of ATP in cell oxidative pathway inhibited cell makes fatty acids stores fat –low ATP in cell oxidative pathway predominates |
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What are the fuel molecules besides glucose? |
- other CHOs - proteins: digested to amino acids --> deaminated --> fed into TCA cycle e.g alanine --> pyruvate; aspartate --> oxaloacetate - fat: digested to fatty acids + glycerol •fatty acids broken down into 2C units --> acetyl-CoA •“b-oxidation” •yield of ATP per 6C fatty acid ~20% higher than that from glucose
•for ATP production, cells first use CHOs, then fats, and finally proteins |
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Glycolysis + TCA Cycle: Key Regulatory Points |
- Cellular needs change •Don’t always need maximal production of energy |
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How do we regulate the flux through glycolysis and the TCA cycle ? |
•Since a pathway is made possible by enzyme catalyzed reactions: •We can regulate the flux through the pathway by regulating the activity of the enzyme’s in the pathway
•glycolysis and the TCA cycle are regulated at several points by substrate availability and feedback (product) inhibition |
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Feedback Inhibition |
•when an enzyme in a pathway is inhibited by a product of that pathway •Product of pathway regulating its own synthesis |
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Regulation of glycolysis |
•during glycolysis, high levels of ATP inhibit the enzyme phosphofructokinase •catalyzes fructose-6-PO4 fructose-1,6-bisPO4 •phosphofructokinase has two binding sites for ATP•the active site and a regulatory (allosteric) site•high [ATP] - ATP also binds at regulatory site•enzyme changes shape reduced activity |
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similarities between chloroplast and mitochondria
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both contain: - inner membrane - outer membrane - intermembrane space - DNA - ribosomes |
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differences between chloroplast and mitochondria |
- mitochondria contains matrix whereas chloroplast contain stroma. - chloroplasts also contains thylakoid space and thylakoid membrane. |
