5.7.2 glycolysis

Question 1

glycolysis

Answer 1

first stage of respiration; 10-stage metabolic pathway that converts glucose to pyruvate

Question 2

where does glycolysis occur

Answer 2

cytoplasm of cells

Question 3

3 main stages of glycolysis

Answer 3

1. phosphorylation of glucose to hexose bisphosphate
2. splitting each hexose bisphosphate molecule into two triose phosphate molecules
3. oxidation of triose phosphate to pyruvate

Question 4

describe step 1: phosphorylation of glucose to hexose bisphosphate

Answer 4

• glucose = hexose sugar (6C)
• 2 molecules of ATP are hydrolysed & released phosphate group added to glucose (6C) forming hexose bisphosphate
• 1 phosphate group at C1 & another at C6

Question 5

describe step 2: splitting the hexose bisphosphate into 2 triose phosphate

Answer 5

• hexose bisphosphate molecule split into two 3C molecules (triose phosphate)

Question 6

describe step 3: oxidation of triose phosphate to pyruvate

Answer 6

(anaerobic but involves oxidation)

1. dehydrogenase enzymes (aided by coenzyme NAD) remove hydrogens from triose phosphate
2. two molecules of NAD accept hydrogen atoms (protons & electrons) & become reduced (NADH)
3. two molecules of NAD reduced for every glucose molecule & four ATP are made for every 2 triose phosphate

Question 7

what happens to glucose

Answer 7

undergoes phosphorylation (adding 2 phosphate molecules - activated) & becomes hexose bisphosphate

Question 8

products of glycolysis

Answer 8

• net gain of 2 molecules of ATP (4 made but 2 used at start)
• 2 molecules of reduced NAD (NADH)
• 2 molecules of pyruvate

Question 9

4 stages of respiration

Answer 9

1. glycolysis
2. link reaction
3. the Krebs cycle
4. oxidative phosphorylation

Question 10

what occurs under aerobic conditions for respiration

Answer 10

1. glycolysis
2. link reaction
3. the Krebs cycle
4. oxidative phosphorylation

Question 11

what occurs under anaerobic conditions for respiration

Answer 11

1. glycolysis
2. lactate fermentation (= lactate) or ethanol fermentation (= ethanol & carbon dioxide)

–> occurs in cytoplasm
–> reduced NAD molecules reoxidised

Question 12

where do pyruvate molecules from glycolysis go

Answer 12

actively transported into mitochondria for link reaction