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What is another name for the citric acid cycle and where does it take place?
- krebs cycle
- takes place within the mitochondrial matrix
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What is the function of the citric acid cycle?
The cycle oxidizes organic fuel from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn.
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What is the total energy yield per glucose molecule in the citric acid cycle?
- 2 FADH2, 2ATP, 6 NADH, 4 CO2 (everything's doubled)
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The citric acid cycle has ___ steps, each catalyzed by a specific enzyme.
eight
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Briefly describe the eight steps in the citric acid cycle. (2)
- The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate.
- the next seven steps decompose the citrate back to oxaloacetate, making the process a cycle.
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What do the NADH and FADH2 produced by the citric acid cycle do?
They relay electrons extracted from food to the electron transport chain.
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What makes the citric acid cycle a cycle?
the regeneration of oxaloacetate
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Citric acid cycle ___________ under anaerobic conditions.
cannot function
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CoA is actually used in how many steps in the citric acid cycle?
- two
- acts as an agent to drive anabolic steo forward
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What happened to the carbons of acetyl CoA in the citric acid cycle?
got turned in to CO2
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What happened in terms of redox reactions in the citric acid cycle
Acetyl CoA fully oxidized, electrons got transferred to NADH+ and FADH2
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Following glycolysis and the citric acid cycle, what accounts for most of the energy extracted from food?
NADH and FADH2
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Where does the electron transport chain take place?
in the inner membrane of the mitochondria
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How do the carriers (proteins) in the electron transport chain alternate as the accept and donate protons?
the carriers alternate reduced and oxidized states as they accept and donate electrons
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Electron drop in energy as they go down the chain and are finally passed to oxygen, forming ___________.
water
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What is a protein used in the electron transport chain?
cytochromes
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The electron transport chain generates how much ATP?
no ATP!
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What is the electron transport chain's function?
it's to break the large free-energy drop from the food to oxygen into smaller steps that release energy in manageable amounts.
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Electron transfer in the electron transport chain causes proteins to do what?
causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space.
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How does H+ then move back across the membrane into the mitochondrial matrix?
by passing through channels in ATP synthase
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what is the function of ATP synthase?
uses exergonic flow of H+ to drive phosphorylation of ATP
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What is example of chemiosmosis?
the use of energy in H+ gradient to drive cellular work.
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What was the net energy yield from the oxidative phosphorylation (per glucose molecule)?
about 34
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Each pair of electrons released by NADH provides enough energy to produce how many ATP?
about 3
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Each pair of electrons released by FADH2 provides enough energy to produce how many ATP?
about 2
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The H+ gradient is referred to as a __________________.
- proton-motive force
- ATP synthesis occurs here
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In cellular respiration, what sequence does most energy flow?
glucose-->NADH-->electron transport chain-->proton-motive force-->ATP
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What is the efficiency of cellular respiration?
about 40%
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Before entering the pathway to cellular respiration, what happens to carbohydrates, amino acids, and fats?
- carbohydrates: converted to glucose
- Amino acids: deaminated
- Fats: undergo beta oxidation
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What is required to keep glycolysis running?
re-oxidizing
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In the absence of oxygen, how is ATP produced?
glycolysis couples with fermentation (anaerobic respiration) to produce ATP
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what does anaerobic respiration use instead of oxygen in the electron transport chain?
an electron acceptor like sulphate
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Fermentation uses __________ instead of an electron transport chain to generate ATP.
phosphorylation
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What are the two types of fermentation?
- Alcohol fermentation
- lactic acid fermentation
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What is alcohol fermentation? give an example.
- pyruvate is converted to ethanol in two steps, while releasing CO2.
- ex. used by yeast in baking
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What is lactic acid fermentation? give an example.
- pyruvate is reduced to lactate to oxidize NAD+. no release of CO2
- ex. used by bacteria to make cheese and yogurt
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What is a similarity between cellular respiration and fermentation?
both process use glycolysis to oxidize glucose and other organic fuels into pyruvate
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What are the final electron acceptors in fermentation and cellular respiration?
- Fermentation: organic molecule (such as pyruvate)
- Cellular respiration: oxygen
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What are obligate anaerobes?(2)
carry out fermentation
cannot survive in the presence of oxygen
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What are facultative anaerobes? Example?
- they can survive using either fermentation OR cellular respirationyeast and many bacteria
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