Module 04 - Glycolysis (Section 02)

Question 1

Where does Glycolysis occur?

Answer 1

in the cytoplasm of cells

Question 2

What happens during Glycolysis?

Answer 2

conversion of one molecule of glucose into two molecules of pyruvate

Question 3

Where is Glycolysis used? Why?

Answer 3

widespread - used in all cells where glucose is broken down to provide ATP and intermediates for other pathways

Question 4

What does the Energy Investment Phase include?

Answer 4

• first 5 reactions
• 2 ATP used

Question 5

What does the Energy Generation Phase include?

Answer 5

• final 5 reactions
• 2 NADH produced
• 4 ATP produced

Question 6

What are the net products of Glycolysis?

Answer 6

• 2 pyruvate
• 2 ATP
• 2 NADH

Question 7

When does the breakdown of glucose occur?

Answer 7

when the cell is in an energy poor state

Question 8

What must the cell invest first to begin the breakdown of glucose?

Answer 8

• 2 ATP molecules
• regulate two enzymes in the process

Question 9

What occurs during the first step of glycolysis?

Answer 9

• phosphate is transferred from ATP and added to glucose to form glucose 6-phosphate (G6P)

Question 10

What is the phosphorylation of glucose reaction catalyzed by? Are they activated or inhibited?

Answer 10

• hexokinase in all cells except liver and pancreas
• glucokinase in liver and pancreas
• inhibited

Question 11

Why is Hexokinase used for Glycolysis?

Answer 11

• has a low Km for glucose, allowing efficient phosphorylation and metabolism of glucose
• has low Vmax, preventing cells from consuming all their cellular phosphate to phosphorylate sugars

Question 12

Why is Glucokinase used for Glycolysis?

Answer 12

• serves as glucose sensor for the liver and pancreas
• high Km, most active when glucose concentrations are high in the body
• high Vmax to allow the liver to quickly remove glucose from circulation after meal

Question 13

What occurs during the third step of glycolysis?

Answer 13

• phosphate from ATP is transferred to fructose 6-P to form fructose 1,6-bisphosphate

Question 14

What enzyme is used the catalyze the phosphorylation of fructose 6-P?

Answer 14

phosphofructokinase-1 (PFK-1)

Question 15

What is PFK-1 activated by? (2)

Answer 15

• allosterically activated by AMP (indicates that cell is in energy poor state)
• activated by fructose 2,6-bisphosphate

Question 16

What is PFK-1 inhibited by?

Answer 16

• its energy substrate ATP and citrate (indicates the cell is in energy rich state)

Question 17

Summarize the energy investment phase of glycolysis.

Answer 17

• 1 molecules of glucose is oxidized to form 2 molecules of glyceraldehyde 3-phosphate
• step 1 and step 3 are the regulatory steps, each requiring the investment of1 molecule of ATP

Question 18

Summarize the energy generation phase of glycolysis.

Answer 18

• begins with 2 molecules of glyceraldehyde 3-P, so all products are doubled from a single glucose molecule
• one regulatory step
• by the end, 2 NADH, 4 ATP, and 2 pyruvate are produced

Question 19

What occurs during the sixth step of glycolysis?

Answer 19

• both molecules of glyceraldehyde 3-P are oxidized for form 1, 3-bisphosphoglycerate by glyceraldehyde 3-P dehydrogenase
• oxideizes the aldehyde and attaches a phosphate
• 1 NAD+ is reduced to NADH for each glyceraldehyde 3-P

Question 20

What occurs during the seventh step of glycolysis?

Answer 20

• high energy phosphate is transferred from 1,3-bisphosphoglycerate to ADP forming 3-phosphoglycerate and ATP

Question 21

What is the dephosphorylation of 1,3-bisphosphoglycerate catalyzed by?

Answer 21

phosphoglycerate kinase

Question 22

How many ATP are produced during step 7 of glycolysis?

Answer 22

• 2 ATP
• at this point, the cell has paid off the ATP debt from the energy investment phase of glycolysis

Question 23

What occurs during the tenth step of glycolysis?

Answer 23

• pyruvate kinase transfers a phosphate from phosphoenolpyruvate to ADP, forming 2 molecules of ATP and 2 molecules of pyruvate
• third irreversible regulatory step

Question 24

What is pyruvate kinase activated by in step 10 of glycolysis? What does this do?

Answer 24

• the product of PFK-1, fructose 1,6-bisphosphate, in a feed-forward mechanism
• accelerates conversion of PEP to pyruvate and ATP, guaranteeing no buildup of glycolytic intermediates

Question 25

What occurs during Aerobic Glycolysis?

Answer 25

• occurs when oxygen is readily available to the cell
• there is sufficient O2 present, therefore NADH produced by glycolysis is passed onto the ETC where it can be re-oxidized
• pyruvate is converted to acetyl-CoA for the TCA cycle

Question 26

What occurs during Anaerobic Glycolysis?

Answer 26

• cells lack the O2 required by the ETC for it to function; must generate NAD+ through alternative pathway
• latase dehydrogenase reduces pyruvate to lactate and oxidized NADH to NAD+

Question 27

How do hormone levels flactuate and regulate glycolysis in the well fed state?

Answer 27

• causes insulin levels in blood to rise
• insulin causes an increase in te levels of glucokinase, PFK, and PK by increasing their rates of synthesis
• increases the rate of glycolysis

Question 28

How do hormone levels flactuate and regulate glycolysis in the fasting state?

Answer 28

• causes glucagon levels in blood to rise
• glucagon decreases the levels of glucokinase, PFK, and PK by decreasing their rates of synthesis
• decreases the rate of glycolysis

Question 29

What are three types og pyruvate kinase defects?

Answer 29

1. Changes in Km or Vmax for enzyme substrates or co-enzymes
2. Alteration in enzyme gene expression or enzyme stability
3. Abnormal response to the activator fructose 1,6-bisphosphate