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Oxidative Phosphorylation and TCA Review
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1
Question
What are the four protein complexes of the inner mitochondrial membrane in the ETC, and which mobile carriers do they interact with?
Answer
Complexes I–IV; interact with CoQ and cytochrome c.
2
Question
Which complex pumps protons at Complex I and how many protons are pumped per NADH oxidized?
Answer
Complex I pumps 4 H+ per NADH.
3
Question
Which complex does not pump protons during electron transfer and why?
Answer
Complex II; electrons flow without proton pumping.
4
Question
What is the role of Coenzyme Q (CoQ) in the ETC?
Answer
Transfers electrons from Complex I/II to Complex III.
5
Question
Which complex is also called cytochrome c oxidase and why?
Answer
Complex IV; reduces O2 to H2O with four electrons.
6
Question
What are the four main protein complexes of the ETC and their primary function?
Answer
I NADH dehydrogenase; II succinate dehydrogenase; III cytochrome bc1; IV cytochrome c oxidase; transfer electrons, pump protons.
7
Question
Name common inhibitors for Complex I, II, III, IV and their effect.
Answer
I: rotenone; II: TTFA; III: antimycin; IV: cyanide—block electron flow.
8
Question
What uncouplers disrupt oxidative phosphorylation and how do they work?
Answer
CCCP, DNP, dicoumarol; dissipate proton gradient, generate heat.
9
Question
Explain the chemiosmotic hypothesis in 2–3 steps.
Answer
Proton gradient drives ATP synthase; protons flow through Fo, rotation of c-ring, F1 catalyzes ADP+Pi to ATP.
10
Question
How many ATP are produced per complete rotation of the Fo c-ring according to textbooks?
Answer
3 ATP per rotation.
11
Question
Which shuttle transfers cytosolic NADH electrons into mitochondria via glycerol-3-phosphate?
Answer
Glycerol phosphate shuttle.
12
Question
What are the two main cytosolic-to-mitochondrial NADH shuttles?
Answer
Glycerol phosphate and malate-aspartate shuttles.
13
Question
In the glycerol phosphate shuttle, what molecule carries electrons into the mitochondrion?
Answer
Glycerol-3-phosphate (converted inside to DHAP).
14
Question
What molecule accepts electrons in Complex I after FMN in the ETC?
Answer
Iron-sulfur centers transfer electrons to CoQ.
15
Question
Why is Complex II not involved in proton pumping?
Answer
Electron transfer from FADH2 to CoQ does not pump protons.
16
Question
What is the role of cytochrome c in the ETC?
Answer
Mobile carrier transferring electrons between Complex III and IV.
17
Question
What is the end product of mitochondrial electron transport with sufficient O2?
Answer
H2O from O2 reduction.
18
Question
What happens to the energy not captured as ATP in oxidative phosphorylation?
Answer
Used for transport and heat generation.
19
Question
Define substrate-level phosphorylation and give two cellular examples.
Answer
Direct phosphate transfer from high-energy donor to substrate; glycolysis and TCA (GTP formation).
20
Question
Name macroergic compounds cited and their role in substrate-level phosphorylation.
Answer
ATP, GTP, creatine phosphate; donate phosphate to substrates.
21
Question
During glycolysis, which step generates ATP via substrate-level phosphorylation?
Answer
1,3-bisphosphoglycerate to 3-PG in glycolysis (phosphorylation step).
22
Question
What is the amphibolic nature of the citric acid cycle?
Answer
TCA is both catabolic and anabolic, supplying energy and biosynthetic precursors.
23
Question
Which enzyme initiates the TCA cycle by condensing acetyl-CoA with oxaloacetate?
Answer
Citrate synthase.
24
Question
Which step in the TCA cycle is a major rate-limiting dehydrogenase producing NADH?
Answer
Isocitrate dehydrogenase.
25
Question
Which molecule is produced with the succinyl-CoA to succinate step, and what is phosphorylated?
Answer
GTP produced; GDP phosphorylated to GTP (substrate-level).
26
Question
Which TCA cycle enzyme is bound to the inner mitochondrial membrane and acts as Complex II?
Answer
Succinate dehydrogenase.
27
Question
What amino acids form oxaloacetate via transamination and deamination pathways?
Answer
Aspartate forms OAA via transamination; Asparagine via asparaginase to aspartate.
28
Question
Which amino acids yield α-ketoglutarate through catabolic routes?
Answer
Gln, Glu, Pro, Arg, His.
29
Question
Which amino acids yield fumarate in their catabolism?
Answer
Phe, Tyr.
30
Question
Which amino acids yield Succinyl-CoA in catabolism?
Answer
Ile, Met, Val, The (threonine via propionyl-CoA).