Respiration (glycolysis, TCA cycle, oxidative phosphorylation)

Question 1

What is the general formula for many carbohydrates?

Answer 1

Cn(H2O)n.

Question 2

What are the main functions of carbohydrates?

Answer 2

Energy storage, signaling, and structural components.

Question 3

Why is glucose considered an excellent fuel?

Answer 3

It yields high energy, stores easily, and can fuel many tissues.

Question 4

What are the four major pathways of glucose utilization?

Answer 4

Storage, glycolysis, pentose phosphate pathway, and synthesis of structural polysaccharides.

Question 5

Where does glycolysis occur in the cell?

Answer 5

In the cytoplasm.

Question 6

What are the two phases of glycolysis?

Answer 6

Preparatory (energy investment) phase and payoff (energy production) phase.

Question 7

What are the products of glycolysis from one glucose molecule?

Answer 7

2 pyruvate, 2 ATP (net), and 2 NADH.

Question 8

What happens in the preparatory phase of glycolysis?

Answer 8

Glucose is phosphorylated and cleaved into two 3-carbon units.

Question 9

What happens in the payoff phase of glycolysis?

Answer 9

ATP and NADH are generated.

Question 10

What are the three key regulatory steps in glycolysis?

Answer 10

Hexokinase, phosphofructokinase-1, pyruvate kinase.

Question 11

What enzyme catalyzes the first step of glycolysis?

Answer 11

Hexokinase.

Question 12

What allosteric activators and inhibitors regulate phosphofructokinase-1?

Answer 12

Activators: AMP, ADP, fructose-2,6-bisphosphate; Inhibitors: ATP, citrate.

Question 13

What does 2,3-bisphosphoglycerate (2,3-BPG) regulate in erythrocytes?

Answer 13

Regulates oxygen release from hemoglobin.

Question 14

What is the Warburg effect?

Answer 14

Cancer cells exhibit high glycolysis even under oxygenated conditions.

Question 15

How is ATP produced in glycolysis?

Answer 15

Via substrate-level phosphorylation.

Question 16

What is anaerobic glycolysis?

Answer 16

Energy production without oxygen by converting pyruvate to lactate or ethanol.

Question 17

What is the fate of pyruvate under anaerobic conditions in humans?

Answer 17

Reduction to lactate to regenerate NAD+.

Question 18

What is the Cori Cycle?

Answer 18

Recycling lactate produced by muscles to glucose in the liver.

Question 19

What is ethanol fermentation?

Answer 19

Conversion of pyruvate to ethanol and CO2 in yeast.

Question 20

What is gluconeogenesis?

Answer 20

The formation of glucose from non-carbohydrate sources.

Question 21

Where does gluconeogenesis mainly occur?

Answer 21

Mainly in the liver, also in the kidneys.

Question 22

What are irreversible steps important for regulating glycolysis and gluconeogenesis?

Answer 22

Steps catalyzed by hexokinase, phosphofructokinase-1, and pyruvate kinase.

Question 23

Why is glycolysis important for metabolism?

Answer 23

Provides ATP, biosynthetic intermediates, and regulates energy homeostasis.

Question 24

What is the main difference between glycolysis and gluconeogenesis?

Answer 24

Glycolysis breaks down glucose for energy; gluconeogenesis synthesizes glucose.

Question 25

Where does the TCA cycle occur in eukaryotic cells?

Answer 25

In the mitochondrial matrix.

Question 26

What molecule enters the TCA cycle?

Answer 26

Acetyl-CoA.

Question 27

What is the main function of the TCA cycle?

Answer 27

To oxidize acetyl-CoA and produce NADH, FADH2, and GTP.

Question 28

What are the products of one turn of the TCA cycle?

Answer 28

2 CO2, 3 NADH, 1 FADH2, 1 GTP (per acetyl-CoA).

Question 29

What enzyme converts pyruvate to Acetyl-CoA?

Answer 29

Pyruvate dehydrogenase complex.

Question 30

How many NADH are generated per turn of the TCA cycle?

Answer 30

3 NADH per turn.

Question 31

What is GTP used for in the TCA cycle?

Answer 31

Can be converted to ATP via nucleoside diphosphate kinase.

Question 32

What is the amphibolic nature of the TCA cycle?

Answer 32

It acts in both catabolic and anabolic pathways.

Question 33

What regulates the TCA cycle?

Answer 33

Substrate availability and product inhibition (e.g., by ATP, NADH).

Question 34

What is anaplerosis?

Answer 34

Replenishment of TCA intermediates from other sources.

Question 35

What enzyme catalyzes the step from α-ketoglutarate to succinyl-CoA?

Answer 35

α-Ketoglutarate dehydrogenase.

Question 36

What is the total ATP yield from two turns of the TCA cycle per glucose?

Answer 36

6 NADH, 2 FADH2, 2 GTP → ~20 ATP total from TCA cycle per glucose.

Question 37

Where does oxidative phosphorylation occur?

Answer 37

In the inner mitochondrial membrane.

Question 38

What are the reduced cofactors that donate electrons to the electron transport chain?

Answer 38

NADH and FADH2.

Question 39

What is the final electron acceptor in oxidative phosphorylation?

Answer 39

Oxygen (O2), which forms water.

Question 40

What is the chemiosmotic theory?

Answer 40

Proton gradients drive ATP synthesis rather than direct coupling.

Question 41

What is the proton-motive force?

Answer 41

An electrochemical gradient of protons across the inner mitochondrial membrane.

Question 42

What are the components of the mitochondrial ATP synthase?

Answer 42

F0 and F1 components.

Question 43

What role does the F0 component of ATP synthase play?

Answer 43

Translocates protons across the membrane.

Question 44

What does the F1 component of ATP synthase do?

Answer 44

Synthesizes ATP from ADP and Pi in the matrix.

Question 45

How does ATP synthase produce ATP?

Answer 45

Via rotation induced by proton flow driving conformational changes.

Question 46

What are the two shuttles that transport electrons into mitochondria from cytosolic NADH?

Answer 46

Malate-aspartate shuttle and glycerol-3-phosphate shuttle.

Question 47

What is the net ATP yield from complete glucose oxidation via aerobic respiration?

Answer 47

30 to 32 ATP depending on shuttle used.

Question 48

What is the function of uncoupling proteins like UCP-1?

Answer 48

Generate heat by dissipating the proton gradient without producing ATP.

Question 49

What are inhibitors of the electron transport chain?

Answer 49

Compounds that block electron flow or proton pumping, stopping ATP synthesis.

Question 50

Why does NADH generate more ATP than FADH2?

Answer 50

NADH donates electrons at Complex I, pumping more protons than FADH2 (which enters at Complex II).

Question 51

What is the Q cycle?

Answer 51

A mechanism in Complex III that facilitates electron transfer and proton pumping.

Question 52

What happens at Complex IV of the electron transport chain?

Answer 52

Electrons from cytochrome c are transferred to O2, forming water and pumping protons.