Week 9

Question 2

Where does glycolysis occur?

Answer 2

Cytosol

Question 3

Why are RBCs a good model for glycolysis?

Answer 3

They lack mitochondria → depend entirely on glycolysis for ATP.

Question 4

Why do RBCs perform only anaerobic glycolysis?

Answer 4

No mitochondria → no TCA cycle or ETC.

Question 5

What is the main function of glycolysis?

Answer 5

Convert glucose → pyruvate with ATP and NADH production.

Question 6

When does anaerobic glycolysis occur?

Answer 6

When oxygen is limited or mitochondria absent.

Question 7

What happens to pyruvate in anaerobic conditions?

Answer 7

Reduced to lactate by lactate dehydrogenase.

Question 8

Why must NADH be reoxidized to NAD+?

Answer 8

NAD+ is required for step 6 (G3P dehydrogenase).

Question 9

What tissues rely heavily on anaerobic glycolysis?

Answer 9

RBCs, lens, cornea, kidney medulla, testes, exercising muscle.

Question 10

What enzyme catalyzes Step 1?

Answer 10

Hexokinase (most tissues) / Glucokinase (liver, β cells)

Question 11

Is Step 1 reversible?

Answer 11

No (irreversible).

Question 12

What inhibits hexokinase?

Answer 12

Glucose-6-phosphate (product inhibition)

Question 13

Key properties of hexokinase?

Answer 13

Low Km, low Vmax, broad specificity.

Question 14

How is glucokinase different?

Answer 14

High Km, high Vmax, not inhibited by G6P.

Question 15

What is Step 2?

Answer 15

G6P → F6P (isomerization).

Question 16

What is the rate-limiting step of glycolysis?

Answer 16

Step 3: PFK-1

Question 17

Reaction of PFK-1?

Answer 17

F6P → F1,6-bisphosphate.

Question 18

What enzyme splits F1,6BP?

Answer 18

Aldolase.

Question 19

What is formed after Step 5?

Answer 19

2 molecules of G3P.

Question 20

What happens in Step 6?

Answer 20

G3P → 1,3-BPG + NADH.

Question 21

What type of reaction is Step 7?

Answer 21

Substrate-level phosphorylation.

Question 22

What happens in Step 10?

Answer 22

PEP → Pyruvate (via pyruvate kinase).

Question 23

Is Step 10 reversible?

Answer 23

No (irreversible).

Question 24

ATP used in glycolysis?

Answer 24

2 ATP (Steps 1 and 3).

Question 25

ATP produced?

Answer 25

4 ATP (2 per each 3-carbon fragment).

Question 26

Net ATP in anaerobic glycolysis?

Answer 26

2 ATP per glucose.

Question 27

What happens to NADH in aerobic glycolysis?

Answer 27

Oxidized via ETC → generates more ATP.

Question 28

Why does anaerobic glycolysis require more glucose?

Answer 28

Only 2 ATP per glucose (less efficient).

Question 29

From which intermediate is 2,3-BPG formed?

Answer 29

1,3-BPG.

Question 30

Which enzyme forms 2,3-BPG?

Answer 30

Bisphosphoglycerate mutase.

Question 31

What is the function of 2,3-BPG?

Answer 31

Decreases hemoglobin affinity for O₂ → increases O₂ delivery.

Question 32

Does the 2,3-BPG shunt produce ATP?

Answer 32

No — it bypasses ATP production.

Question 33

Why is 2,3-BPG high in PK deficiency?

Answer 33

Compensatory increase to improve O₂ delivery.

Question 34

How is hexokinase regulated?

Answer 34

Product inhibition by G6P.

Question 35

Is glucokinase inhibited by G6P?

Answer 35

No.

Question 36

What regulates glucokinase?

Answer 36

GKRP (glucokinase regulatory protein).

Question 37

What happens to glucokinase when glucose is high?

Answer 37

Released from GKRP → active in cytosol.

Question 38

What inhibits PFK-1?

Answer 38

ATP, citrate.

Question 39

What activates PFK-1?

Answer 39

AMP, fructose-2,6-bisphosphate.

Question 40

What does high ATP signal?

Answer 40

Energy sufficient → inhibit glycolysis.

Question 41

What hormone increases fructose-2,6-BP?

Answer 41

Insulin.

Question 42

What hormone decreases fructose-2,6-BP?

Answer 42

Glucagon.

Question 43

What activates pyruvate kinase?

Answer 43

Fructose-1,6-bisphosphate (feed-forward activation).

Question 44

What inhibits liver pyruvate kinase?

Answer 44

Phosphorylation via cAMP (glucagon effect).

Question 45

What does glucagon do to PK?

Answer 45

Inactivates it → promotes gluconeogenesis.

Question 46

What does insulin do to glycolytic enzymes?

Answer 46

Increases synthesis of glucokinase, PFK-1, PK.

Question 47

What does glucagon promote?

Answer 47

Gluconeogenesis and inhibition of glycolysis.

Question 48

What type of anemia occurs?

Answer 48

Chronic hemolytic anemia.

Question 49

Why do RBCs lyse in PK deficiency?

Answer 49

↓ ATP → membrane instability → splenic destruction.

Question 50

Why is severity variable?

Answer 50

Depends on residual enzyme activity + 2,3-BPG compensation.

Question 51

What enzyme does fluoride inhibit?

Answer 51

Enolase.

Question 52

Why is fluoride used in blood collection tubes?

Answer 52

Prevents glycolysis after sample collection.

Question 53

How does arsenate affect glycolysis?

Answer 53

Replaces Pi in Step 6 → no ATP formed.

Question 54

What is the effect?

Answer 54

Glycolysis proceeds but no net ATP gain.

Question 55

Causes of lactic acidosis?

Answer 55

MI, shock, PE, hemorrhage, hypoxia.

Question 56

Why does hypoxia cause lactic acidosis?

Answer 56

Impaired ETC → ↑ anaerobic glycolysis → lactate accumulation.

Question 57

Why does thiamine deficiency cause lactic acidosis?

Answer 57

Impaired PDH → pyruvate accumulates → converted to lactate.

Question 58

Calculate ATP from 1 glucose anaerobically.

Answer 58

4 produced – 2 used = 2 ATP net.