Test 3: Glycolysis

Question 1

What is glycolysis?

Answer 1

• first metabolic pathway
• metabolises 1 molecule of glucose into 2 molecules of puruvate
• produces 8 ATP
• anaerobic process

Question 2

What is the first metabolic pathway?

Answer 2

glycolysis

Question 3

What are the products and reactants of Glycolysis?

Answer 3

reactant: 1 glucose
product: 2 pyruvate + 8ATP

Question 4

How many molecules of ATP does glycolysis yield?

Answer 4

8 molecules of ATP

Question 5

Is glycolysis aerobic or anaerobic?

Answer 5

anaerobic

Question 6

What can happen after glycolysis to the pyruvate molecules? (with and without oxygen presence)

Answer 6

anaerobically:
pyruvate is fermented into lactate or ethanol and CO2

aerobically:
pyruvate is completely oxidised to carbon dioxide, generating more ATP

Question 7

State the anaerobic reactions of pyruvate.

Answer 7

2pyruvate –> 2ethanol + 2CO2
2pyruvate –> 2lactate

Question 8

State the aerobic reactions of pyruvate.

Answer 8

2pyruvate –> 2acetyl-CoA –> 4CO2 + 4H2O

Question 9

How many enzyme catalysed reactions are there in glycolysis? How many stages are they divided into? What is the stage-division based on?

Answer 9

10 enzyme catalysed reactions
2 stages

STAGE 1 (preparatory phase):
- glucose –> 2G3P
- (loss of 2 ATP)

STAGE 2 (payoff phase):
- 2G3P –> 2pyruvate
- (gain 4 ATP and 2 NADH)

Question 10

What are the major steps of stage 1?

Answer 10

1) phosphorylation of glucose –> glucose 6-phosphate
2) isomerization of G6P –> fructose 6-phosphate
3) transpher of phosphoryl group from ATP to C’1 –> fructose 1,6-bisphosphate
4) cleavage of fructose 1,6-bisphosphate –> glyceraldehyde 3 phosphate (aldose) + dihydroxy acetone phosphate (ketose)
5) triose phosphate mutose reaction: dihydroxy acetone phosphate (ketose) –> glyceraldehyde 3 phosphate (aldose)

Question 11

What catalyses step 1?

Answer 11

glucose hexokinase

Question 12

What catalyses step 2?

Answer 12

• phosphohexose isomerase
• Mg2+

Question 13

What catalyses step 3?

Answer 13

• phosphofructokinase
• Mg2+
  (ATP –> ADP + Pi)

Question 14

What catalyses step 4?

Answer 14

aldolase

Question 15

What catalyses step 5?

Answer 15

triose phosphate isomerase

Question 16

What are the major steps of stage 2?

Answer 16

6) glyceraldehyde-3-phosphate dehydrogenase reaction: G3P + Pi –> 1,3-bisphosphoglycerate
7) phosphoglycerate kinase reaction: 1,3-bisphosphoglycerate + ADP –> 3-phosphoglycerate + ATP
8) phosphoglycerate mutase reaction:–> 2-phosphoglycerate (2PG)
9) dehydration: –> phosphoenolpyruvate (PEP)
10) pyruvate kinase reaction: PEP + ADP –> pyruvate + ATP

Question 17

What catalyses step 6?

Answer 17

• glyceraldehyde 3-phosphate degydrogenase
• (NAD+ –> NADH + H+)

Question 18

What catalyses step 7?

Answer 18

• phosphoglycerate kinase
• Mg2+

Question 19

What catalyses step 8?

Answer 19

• phosphoglycerate mutase
• Mg2+

Question 20

What catalyses step 9?

Answer 20

• enolase
• H2O lost (dehydration)

Question 21

What catalyses step 10?

Answer 21

• pyruvate kinase
• Mg2+
• K+

Question 22

What are the two forms of pyruvate? How to tell them apart?

Answer 22

keto:
- -CH3 group and =O group
- (no -OH group)

enol:
-OH group and =CH2

Question 23

How is lactate formed?

Answer 23

reactant: pyruvate
product: lactate
enzyme: lactate dehydrogenase

other reaction: NADH + H+ –> NAD+

Question 24

How does alcoholic fermentation occur?

Answer 24

2 step process

1) pyruvate –> acetalaldehyde
enzyme: pyruvate decarboxylase

2) acetalaldehyde –> ethanol
enzyme: alcohol dehydrogenase

Question 25

Explain the importance of glycolysis.

Answer 25

• only pathway taking place in all body cells
• only energy source in erythrocytes
• anaerobic glycolysis: major muscle energy when oxygen is lacking
• provides carbon skeletons for synthesis of non-essential amino acids and glycerol
• reversable (in gluconeogenesis)

Question 26

What are the 3 stages of cellular respiration? Where do they occur?

Answer 26

1) acetyl-CoA production (in cytosol)
2) acetyl-CoA oxidation (mitochondria)
3) electron transfer and oxidative phosphorylation (mitochondria)

Question 27

What is FAD?

Answer 27

Flavin Adenine Dinucleotide
- derived from riboflavin
- part of E3
- FAD + 2e- + 2H+ <->FADH2

Question 28

Explain the energy produced in the Cytric Acid Cycle.

Answer 28

3NADH (3,4,8) –> 9ATP
1FADH2 (6) –> 2ATP
1GTP (5) –> 1ATP

Question 29

Explain the energy yield of aerobical Glycolysis.

Answer 29

1: - 1ATP
3: - 1ATP
6: +6ATP (2NADHx3ATP)
7: +2ATP (2x1ATP)
10: +2ATP (2x1ATP)

TOTAL: 8ATP

Question 30

Explain the energy yield of anaerobical Glycolysis.

Answer 30

1: - 1ATP
3: - 1ATP
6: +6ATP (2NADHx3ATP)
7: +2ATP (2x1ATP)
10: +2ATP (2x1ATP)
11: -6ATP (2NADHx3ATP) (pyruvate –> lactate)

TOTAL: 8ATP

Question 31

What is the total energy yield when converting glucose to CO2 and H2O?

Answer 31

glycolysis (aerobic): +8ATP
piruvate decarboxylation: +6ATP
(2NADHx3ATP)
TAC: +24ATP

TOTAL: 38ATP