Glycolysis

Question 1

Where does glycolysis occur?

Answer 1

Cytosol

Question 2

Does glycolysis occur aerobically or anaerobically?

Answer 2

BOTH

(Glycolysis occurs both aerobically and anaerobically.)

Question 3

What is the function of a kinase?

Answer 3

Transfers/adds phosphate groups (phosphorylation).

Question 4

What is the main purpose of glycolysis?

Answer 4

Glucose is converted into 2 three-carbon pyruvate molecules.

Question 5

What are the five most important enzymes in glycolysis?

Answer 5

1. hexokinase OR glucokinase
2. PFK-1
3. Glyceraldehyde-3-phosphate (G3P) dehydrogenase
4. 3-phosphoglycerate kinase
5. pyruvate kinase

Question 6

Which enzyme is the rate limiting enzyme and main control point of glycolysis?

Answer 6

PFK-1

Once this reaction occurs, glucose is committed to glycolysis.

Question 7

What are the three irreversible enzymes of glycolysis?

Answer 7

1. hexokinase OR glucokinase
2. PFK-1
3. pyruvate kinase

Question 8

In glycolysis, what effect does hexokinase or glucokinase have on glucose?

Answer 8

Adds a phosphate group to glucose which “traps” it inside the cell.

Glucose becomes glucose-6-p.

Question 9

How is ATP produced in anaerobic glycolysis?

Answer 9

Via substrate-level phosphoryation

ADP is phosphorylated into ATP.

Question 10

Both hexokinase and glucokinase function in glycolysis by phosphorylating glucose. Where exactly do they function?

Answer 10

Hexokinase: in most tissues

Glucokinase: in liver cells and pancreatic β-islet cells

Question 11

1,3-bisphosphoglycerate is an important molecule in glycolysis. Which two molecules does it produce?

Answer 11

1. ATP
2. NADH

Question 12

In glycolysis, what is the process of feed forward activation?

Answer 12

When an earlier step activates a later step.

Fructose 1,6-bisphosphate from the PFK-1 reaction activates pyruvate kinase.

Question 13

PFK-1 is the rate-limiting enzyme of glycolysis and is able to regulate it through allosteric inhibition. Which three molecules inhibit PFK-1?

Answer 13

1. glucagon
2. ATP
3. citrate

Question 14

PFK-1 is the rate-limiting enzyme of glycolysis and is able to regulate it through allosteric inhibition. Which three molecules activate PFK-1?

Answer 14

1. insulin
2. AMP
3. F 2,6-BP

Question 15

In glycolysis, what is the main function of the enzymes 3-phosphoglycerate kinase and pyruvate kinase?

Answer 15

Generate ATP via substrate-level phosphorylation.

Question 16

Does fermentation occur aerobically or anaerobically?

Answer 16

Anaerobically

(Fermentation is anaerobic glycolysis.)

Question 17

What is the main purpose of fermentation?

Answer 17

Replenishes NAD⁺ to continue glycolysis.

Pyruvate from glycolysis is used to oxidize NADH to NAD⁺.

Question 18

For fermentation, the conversion of pyruvate is different in animal and yeast cells. What does each cell convert pyruvate into?

Answer 18

animal cells: pyruvate → lactate

yeast cells: pyruvate → ethanol and CO₂

Question 19

In animal cells, which enzyme is the rate limiting enzyme of fermentation?

Answer 19

Lactate dehydrogenase

NADH is oxidized to NAD⁺.

Question 20

Pyruvate from aerobic glycolysis has different fates. What are the three fates?

Answer 20

1. converted to acetyl-CoA by PDH for the citric acid cycle
2. converted to lactate by LDH for fermentation
3. converted to oxaloacetate (OAA) by pyruvate carboxylase for gluconeogenesis

Question 21

Pyruvate from aerobic glycolysis may be converted to acetyl-CoA for entry into the citric acid cycle if ATP is needed. Where does this conversion occur?

Answer 21

Mitochondrial matrix

Question 22

For galactose metabolism, which enzyme adds a phosphate group to galactose “trapping” it inside of the cell? Fructose metabolism?

Answer 22

galactose metabolism: Galactokinase

fructose metabolism: Fructokinase