Week 9

Question 1

What is aerobic glycolysis?

Answer 1

Glycolysis occurring in the presence of oxygen where pyruvate enters mitochondria → Acetyl-CoA → TCA cycle.

Question 2

What is anaerobic glycolysis?

Answer 2

Glycolysis occurring without oxygen where pyruvate is converted to lactate to regenerate NAD⁺.

Question 3

Why must NAD⁺ be regenerated in anaerobic glycolysis?

Answer 3

NAD⁺ is required for Step 6 (G3P dehydrogenase) to continue glycolysis.

Question 4

Which tissues rely on anaerobic glycolysis?

Answer 4

RBCs, lens, cornea, kidney medulla, testes, exercising skeletal muscle, some cancers.

Question 5

How many steps are in glycolysis?

Answer 5

10 steps.

Question 6

What are the three phases of glycolysis?

Answer 6

1. Energy investment 2. Splitting phase 3. Energy payoff

Question 7

What is the rate-limiting step of glycolysis?

Answer 7

Step 3: F6P → F1,6BP via PFK-1.

Question 8

What regulates PFK-1?

Answer 8

Activated by: AMP, Fructose-2,6-bisphosphate Inhibited by: ATP, Citrate

Question 9

What are the 3 irreversible steps of glycolysis?

Answer 9

Step 1 – Hexokinase/Glucokinase Step 3 – PFK-1 Step 10 – Pyruvate kinase

Question 10

What is the difference between hexokinase and glucokinase?

Answer 10

Hexokinase: • Low Km (high affinity) • Low Vmax • Inhibited by G6P • Present in most tissues Glucokinase: • High Km (low affinity) • High Vmax • Not inhibited by G6P • Present in liver & β-cells

Question 11

How is hexokinase regulated?

Answer 11

Product inhibition by glucose-6-phosphate.

Question 12

How is glucokinase regulated?

Answer 12

By GKRP (glucokinase regulatory protein) and insulin (increases synthesis).

Question 13

How is pyruvate kinase (PK) regulated?

Answer 13

Activated by: Fructose-1,6-bisphosphate (feed-forward) Inhibited by: Phosphorylation via glucagon (in liver)

Question 14

What is the effect of arsenic poisoning on glycolysis?

Answer 14

Arsenate replaces Pi in Step 6 → ATP is not formed → ↓ net ATP.

Question 15

What enzyme does fluoride inhibit?

Answer 15

Enolase (Step 9).

Question 16

Why is fluoride used in blood collection tubes?

Answer 16

To prevent glycolysis after blood is drawn.

Question 17

What is the link between glycolysis and dental caries?

Answer 17

Oral bacteria metabolize glucose via glycolysis → produce lactic acid → enamel demineralization.

Question 18

What is the net ATP yield of anaerobic glycolysis?

Answer 18

2 ATP per glucose.

Question 19

What are the net products of anaerobic glycolysis?

Answer 19

2 Lactate + 2 ATP.

Question 20

What are the net products of aerobic glycolysis?

Answer 20

2 Pyruvate + 2 ATP + 2 NADH.

Question 21

What are causes of lactic acidosis?

Answer 21

• Hypoxia • Shock • Myocardial infarction • Pulmonary embolism • Severe anemia • Thiamine deficiency

Question 22

What is the 2,3-BPG shunt?

Answer 22

A pathway in RBCs where 1,3-BPG → 2,3-BPG to decrease hemoglobin’s oxygen affinity (bypasses ATP production).

Question 23

What is the cause of pyruvate kinase (PK) deficiency?

Answer 23

Genetic mutation causing reduced PK enzyme activity (usually autosomal recessive).

Question 24

Why does PK deficiency cause hemolytic anemia?

Answer 24

↓ ATP in RBCs → membrane instability → splenic destruction.

Question 25

What are symptoms of PK deficiency?

Answer 25

Chronic hemolytic anemia, jaundice, fatigue, splenomegaly.

Question 26

Is there treatment for PK deficiency?

Answer 26

• Blood transfusions (severe cases) • Splenectomy (sometimes) • Supportive care

Question 27

Step 1 of glycolysis?

Answer 27

**Glucose → Glucose-6-phosphate (G6P)** Enzyme: Hexokinase (or Glucokinase in liver) Uses 1 ATP Irreversible

Question 28

Step 2 of glycolysis?

Answer 28

**Glucose-6-phosphate → Fructose-6-phosphate** Enzyme: Phosphoglucose isomerase Reversible

Question 29

Step 3 of glycolysis?

Answer 29

**Fructose-6-phosphate → Fructose-1,6-bisphosphate** Enzyme: PFK-1 Uses 1 ATP Rate-limiting step Irreversible

Question 30

Step 4 of glycolysis?

Answer 30

**Fructose-1,6-bisphosphate → DHAP + G3P** Enzyme: Aldolase Reversible

Question 31

Step 5 of glycolysis?

Answer 31

**DHAP → G3P** Enzyme: Triose phosphate isomerase Reversible Now you have **2 G3P molecules**

Question 32

Step 6 of glycolysis?

Answer 32

**G3P → 1,3-bisphosphoglycerate (1,3-BPG)** Enzyme: Glyceraldehyde-3-phosphate dehydrogenase Produces NADH Requires NAD⁺ Reversible

Question 33

Step 7 of glycolysis?

Answer 33

**1,3-BPG → 3-phosphoglycerate** Enzyme: Phosphoglycerate kinase Produces ATP Substrate-level phosphorylation Reversible

Question 34

Step 8 of glycolysis?

Answer 34

**3-phosphoglycerate → 2-phosphoglycerate** Enzyme: Phosphoglycerate mutase Reversible

Question 35

Step 9 of glycolysis?

Answer 35

**2-phosphoglycerate → Phosphoenolpyruvate (PEP)** Enzyme: Enolase Releases H₂O Reversible Inhibited by fluoride

Question 36

Step 10 of glycolysis?

Answer 36

**PEP → Pyruvate** Enzyme: Pyruvate kinase Produces ATP Irreversible

Question 37

Irreversible steps

Answer 37

1, 3, 10 (Hexokinase, PFK-1, Pyruvate kinase)

Question 38

ATP used

Answer 38

Steps 1 & 3

Question 39

ATP made

Answer 39

Steps 7 & 10

Question 40

NADH made

Answer 40

Step 6