Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
162 Cards in this Set
- Front
- Back
What is cellular metabolism?
|
It is the sum of all chemical reactions that take place in the cell
|
|
What are these reactions generally categorized as?
|
Anabolic or catabolic
|
|
Which requires energy?
|
Anabolic requires energy
|
|
What does it involve?
|
It is the biosynthesis of complex organic compounds from simpler molecules
|
|
What is catabolism?
|
It releases energy as they break down complex organic compounds into smaller molecules
|
|
What are autotrophic organisms?
|
They convert sunlight into bond energy
|
|
What is an example?
|
Green plants
|
|
What type of bond energy is sunlight converted into?
|
It is converted into the bond energy in the bonds of organic compounds like glucose
|
|
When does this occur?
|
During the anabolic process of photosynthesis
|
|
Because of this, what do autotrophs not need?
|
They do not need an exogenous supply of organic compounds
|
|
What are heterotrophic organisms?
|
They obtain their energy catabolically, via the breakdown of organic nutrients that must be ingested
|
|
What is the net reaction of photosynthesis?
|
6CO2 + 6H20 + Energy à C6H12O6 + 6O2
|
|
Why do heterotrophic organisms metabolize glucose and other organic molecules?
|
They do it to release the stored bond energies
|
|
What is the net reaction of glucose catabolism?
|
C6H12O6 + 6O2 à 6CO2 + 6H20 + Energy
|
|
What is interesting about this reaction?
|
It’s basically the backward reaction of Photosynthesis!
|
|
What are some of the various molecular carriers used to shuttle energy between reactions?
|
ATP is one of them, along with the coenzymes NAD+, NADP+, and FAD
|
|
What is ATP?
|
Adenosine triphosphate is the cell’s main energy currency
|
|
What happens through its formation and degradation?
|
Cells have a quick way of releasing and storing energy
|
|
How is ATP synthesized?
|
It occurs during glucose catabolism
|
|
What is ATP composed of?
|
It has the nitrogenous base adenine, the sugar ribose, and three weakly linked phosphate groups
|
|
Where is the energy of ATP stored?
|
In the covalent bonds attaching the phosphate groups
|
|
What are they often referred to as?
|
High-energy bonds
|
|
What does hydrolysis of ATP to ADP and Pi release?
|
It releases stored bond energy that the cell can use in metabolic processes
|
|
How many kcal of energy are released per mole of ATP?
|
Approximately 7kcal of energy
|
|
What does this energy provide for?
|
Endergonic (endothermic) reactions such as muscle contraction, motility, and the active transport of substances across plasma membranes
|
|
What can ATP be hydrolyzed into?
|
AMP and PPi
|
|
What do ADP and Pi combine to form?
|
ATP
|
|
What is the purpose of this?
|
To regenerate its ATP supply
|
|
Does this process require energy?
|
Yes
|
|
Where does the necessary input of energy come from?
|
It comes from the degradation of glucose
|
|
What is a second mechanism by which the cell stores chemical energy?
|
It stores energy in the form of high potential electrons
|
|
What are electrons transferred as?
|
Hydride ions (H:-) or as pairs of hydrogen atoms
|
|
What happens during glucose oxidation?
|
Hydrogen atoms are removed
|
|
What happens to these hydrogen atoms?
|
They are accepted by NAD+, FAD, and NADP+
|
|
What do these molecules do?
|
They transport the high-energy electrons of the hydrogen atoms to a series of carrier molecules on the inner mitochondrial membrane
|
|
What are the carrier molecules known as?
|
The electron transport chain
|
|
What is oxidation?
|
It is the loss of an electron
|
|
What are NAD+, NADP+, and FAD referred to as?
|
Oxidizing agents
|
|
Why?
|
Because they cause other molecules to lose electrons and undergo oxidation
|
|
In the process what do they themselves undergo?
|
Reduction
|
|
What does this mean?
|
They gain electrons
|
|
What do NADH, NADPH, and FADH2 all behave as?
|
Reducing agents
|
|
What does NADH transfer its electrons to?
|
Another electron acceptor, thereby reducing it, and in the process NADH is oxidized back to NAD+
|
|
So, what do these coenzymes ultimately do?
|
They temporarily store and release energy in the form of electrons through their successive oxidations and reductions
|
|
What are the two stages of the degradative oxidation of glucose?
|
Glycolysis and cellular respiration
|
|
What is the first stage of glucose catabolism?
|
Glycolysis
|
|
What is glycolysis?
|
A series of reactions that lead to the oxidative breakdown of glucose into two molecules of pyruvate
|
|
What else is produced besides pyruvate?
|
ATP
|
|
What is reduced?
|
NAD+ becomes NADH
|
|
Where do all of these reactions take place?
|
In the cytoplasm
|
|
What are they mediated by?
|
Specific enzymes
|
|
How many molecules of PGAL are formed per molecule of glucose?
|
2 molecules
|
|
From one molecule of glucose, how many molecules of pyruvate are obtained?
|
2 molecules
|
|
How many ATP are used?
|
2 ATP
|
|
How many ATP are generated?
|
4 ATP are generated
|
|
What is the net production of ATP?
|
2 ATP per glucose molecule
|
|
What is this type of phosphorylation called?
|
It is called substrate level phosphorylation
|
|
Why?
|
Because since ATP is directly coupled with the degradation of glucose without the participation of an intermediate molecule such as NAD+
|
|
How many NADH is produced per PGAL?
|
1 NADH
|
|
What is the total production of NADH?
|
2 NADH molecules per glucose
|
|
What is the net reaction of glycolysis?
|
Glucose + 2ADP + 2Pi + 2NAD+ à 2 Pyruvate + 2ATP + 2NADH + 2H+ + 2H20
|
|
Does this occur in eukaryotes and prokaryotes or just eukaryotes?
|
It takes place in both kinds
|
|
Where can pyruvate degradation occur from this point?
|
It can occur to fermentation or cellular respiration in the mitochondria
|
|
What causes it to go the fermentation route?
|
If it is an anaerobic environment
|
|
What about toward the cellular respiration route in the mitochondria?
|
If there is oxygen the route will be this way
|
|
What is fermentation?
|
This is the reduction of pyruvate into ethanol or lactic acid
|
|
Why does this occur?
|
Because NAD+ must be regenerated for glycolysis to continue in the absence of O2
|
|
How many ATP does fermentation produce per glucose molecule?
|
It produces 2 ATP total
|
|
What is alcoholic fermentation?
|
It is a type that commonly occurs only in yeast and some bacteria
|
|
What occurs?
|
The pyruvate produced in glycolysis is decarboxylated to become acetaldehyde
|
|
Then what happens?
|
The acetaldehyde is reduced by the NADH generated in glycolysis to yield ethanol
|
|
What does this produce?
|
It produces NAD+ so that glycolysis can continue
|
|
What is lactic acid fermentation?
|
It occurs in certain fungi and bacteria
|
|
When does it occur in humans?
|
It occurs during strenuous activity
|
|
Why would it occur then?
|
It occurs then because during that time the oxygen supply to muscle cells lags behind the rate of glucose catabolism
|
|
What happens here?
|
The pyruvate generated is reduced to lactic acid
|
|
What is a similar thing that occurs between this an alcoholic fermentation?
|
They both include the regeneration of NAD+ when pyruvate is reduced
|
|
What may accumulate in humans during exercise as a result of this type of fermentation?
|
Lactic acid
|
|
What happens then?
|
The pH goes down in the blood, which causes muscle fatigue
|
|
What happens when the oxygen supply is replenished?
|
The lack acid is oxidized back to pyruvate and the cell enters cellular respiration
|
|
What is the amount of oxygen needed for this conversion to occur called?
|
Oxygen debt
|
|
What is cellular respiration?
|
It is the most efficient catabolic pathway used by organisms to harvest energy stored in glucose
|
|
How much energy does cellular respiration yield?
|
36-38ATP
|
|
What type of process is it?
|
It is an aerobic process
|
|
What does oxygen act as?
|
It acts as the final acceptor of electrons that are passed from carrier to carrier during the final stage of glucose oxidation
|
|
Where does it occur?
|
It occurs in eukaryotic mitochondrion
|
|
What is it catalyzed by?
|
Reaction-specific enzymes
|
|
What are the three stages of cellular respiration?
|
Pyruvate decarboxylation, the citric acid cycle, and the electron transport chain
|
|
What happens during pyruvate decarboxylation?
|
The pyruvate formed during glycolysis is transported from the cytoplasm into the mitochondrial matrix where it is decarboxylated
|
|
What does this mean?
|
It means it loses its CO2
|
|
What happens to the remaining acetyl group?
|
It is transferred to coenzyme A to form acetyl CoA
|
|
During this process, what happens to NAD+?
|
It is reduced to NADH
|
|
What is the citric acid cycle also known as?
|
It is known as the Krebs cycle or the tricarboxylic acid cycle
|
|
When does the cycle begin?
|
It begins when the two carbon acetyl group from acetyl CoA combined with oxaloacetate
|
|
What is oxaloacetate?
|
A four-carbon molecule
|
|
What does this form?
|
It forms the six-carbon citrate
|
|
What happens during the series of reactions that follow?
|
2 CO2 are released, and oxaloacetate is regenerated for use in another turn of the cycle
|
|
How many ATP are produced per turn of the cycle?
|
1 ATP is produced
|
|
What type of phosphorylation occurs here?
|
Substrate level phosphorylation
|
|
What happens to NAD+ and FAD during the cycle?
|
Electrons are transferred to them, making NADH and FADH2
|
|
Where do these coenzymes transport the electrons to?
|
They transport the electrons to the electron transport chain, where more ATP is produced
|
|
How is it produced?
|
Through oxidative phosphorylation
|
|
Per molecule of glucose, how many pyruvates are decarboxylated and channeled into the citric acid cycle?
|
2 Pyruvates
|
|
What is the net reaction of the citric acid cycle per glucose molecule?
|
2 Acetyl CoA + 6NAD+ + 2FAD + 2GDP + 2Pi + 4H2O --> 4CO2 + 6NADH + 2FADH2 + 2ATP + 4H+ + 2CoA
|
|
What is the electron transport chain?
|
It is a complex carrier mechanism located on the inside of the inner mitochondrial membrane
|
|
What happens during oxidative phosphorylation?
|
ATP is produced when high energy potential electrons are transferred from NADH and FADH2 to oxygen by a series of carrier molecules located in the inner mitochondrial membrane
|
|
What happens as electrons are transferred from carrier to carrier?
|
Free energy is released
|
|
What is this new free energy used for?
|
It is used to form ATP
|
|
What are most of the molecules in the ETC chain called?
|
They are mostly cytochromes
|
|
What are those?
|
They are electron carriers that resemble hemoglobin in the structure of their active site
|
|
What does the functional unit contain?
|
A central iron atom, which is capable of undergoing a reversible redox reaction
|
|
What does that mean?
|
It means that is can alternatively be reduced and oxidized
|
|
What is FMN or flavin mononucleotide?
|
It is the first molecule of the ETC
|
|
What happens to it when it accepts electrons from NADH?
|
It is reduced
|
|
What happens to NADH?
|
It is reduced from NADH to NAD+
|
|
What is the last carrier of the ETC?
|
Cytochrome a3
|
|
What does it do?
|
It passes its electron to the final electron acceptor, O2
|
|
What else does the O2 pick up besides electrons?
|
It also picks up a pair of hydrogen ions from the surrounding medium
|
|
What does this form?
|
H2O
|
|
What happens if there is no oxygen?
|
The ETC becomes backlogged with electrons
|
|
What does this do?
|
NAD+ cannot be regenerated and glycolysis cannot continue unless lactic acid fermentation occurs
|
|
What does cyanide or dinitrophenol do?
|
They stop ATP synthesis
|
|
Why?
|
They are known as respiratory poisons
|
|
How do they work?
|
Cyanide blocks the transfer of electrons from cytochrome a3 to O2. Dinitrophenol uncouples the electron transport chain from the proton gradient established across the inner mitochondrial membrane
|
|
What are the three large protein complexes that electron carriers are classified as?
|
NADH dehydrogenase, the b-c1 complex, and cytochrome oxidase
|
|
An electron passing through the entire ETC supplies enough energy to generate how many ATP?
|
3 ATP
|
|
NADH delivers its electrons to NADH dehydrogenase complex, which produces how many ATP?
|
For each NADH, 3 ATP are produced
|
|
What does FADH2 do that is different?
|
It bypasses the NADH dehydrogenase complex and delivers its electrons directly to carrier Q
|
|
What is carrier Q?
|
It is called ubiquinone, which lays between the NADH dehydrogenase and b-c1 complexes
|
|
For each FADH2, how many energy drops and corresponding ATPs are produced?
|
2 energy drops, so 2 ATPs are produced
|
|
What does the operating mechanism in this type of ATP production involve?
|
The coupling of oxidation of NADH to the phosphorylation of ADP
|
|
What is the coupling agent for these two things?
|
The proton gradient across the inner mitochondrial membrane
|
|
What is it maintained by?
|
The electron transport chain
|
|
What happens as NADH passes its electrons to the ETC?
|
Free hydrogen ions are released and accumulate in the mitochondrial matrix
|
|
What does the ETC do to these ions?
|
It pumps them out of the matrix, across the inner mitochondrial membrane, and into the intermembrane space at each of the three protein complexes
|
|
What does this continuous translocation of H+ create?
|
A positively charged acidic environment in the intermembrane space
|
|
What does the electrochemical gradient generate?
|
A proton-motive force
|
|
What is that?
|
It is what drives the H+ back across the inner membrane and into the matrix
|
|
There is a problem, what is it?
|
To pass through the membrane which is impermeable to ions, the H+ must flow through specialized channels provided by enzyme complexes
|
|
What are the enzyme complexes called?
|
ATP synthetases
|
|
What happens as the H+ passes through the ATP synthetases?
|
Energy is released to allow for phosphorylation of ADP to ATP
|
|
What is the coupling of the oxidation of NADH with the phosphorylation of ADP called?
|
Oxidative phosphorylation
|
|
What happens when glucose supplies run low?
|
The body utilizes other energy sources
|
|
What are the sources used by the body?
|
It uses carbohydrates first, then fats, then proteins
|
|
How does it work?
|
These substances are first converted to either glucose or glucose intermediates, which can be then degraded in the glycolytic pathway and the TCA cycle
|
|
How does it work with carbohydrates?
|
Disaccharides are hydrolyzed into monosaccharides, most of which can be converted into glucose or glycolytic intermediates
|
|
What can glycogen in the liver be converted into?
|
When needed, it can be converted into glucose-6-phosphate, a glycolytic intermediate
|
|
What about fats?
|
Fat molecules are stored in adipose tissue in the form of triglyceride. When needed, they are hydrolyzed by lipases to fatty acids and glycerol, and are carried by the blood to other tissues for oxidation
|
|
What can glycerol be converted into?
|
PGAL, a glycolytic intermediate
|
|
What must first happen for the fatty acid?
|
It must be activated in the cytoplasm
|
|
What does this process require?
|
2ATP
|
|
Once activated, what occurs?
|
The fatty acid is transported into the mitochondrion and taken through a series of beta-oxidation cycles
|
|
What do the cycles do?
|
They convert it into two-carbon fragments
|
|
What happens to them?
|
They are converted into acetyl CoA
|
|
What happens to the acetyl CoA?
|
It enters the Citric Acid Cycle
|
|
With each round of beta-oxidation of a saturated fatty acid, what is generated?
|
1 NADH and 1 FADH2
|
|
What yields the largest number of ATP per gram?
|
Fats
|
|
What does this imply?
|
It means they are extremely efficient energy storage molecules
|
|
How do proteins get converted?
|
The body degrades amino acids only when there is not enough carbohydrate available
|
|
How does this occur?
|
Most undergo a transamination reaction
|
|
What happens with one of those?
|
They lose an amino group to form an alpha-keto acid
|
|
What happens to the carbon atoms of most amino acids?
|
Most are converted into acetyl-CoA, pyruvate, or one of the intermediates of the citric acid cycle
|