Glycolysis

Question 1

Basic outline of glycolysis

Answer 1

Produces ATP without O2 and mitochondria but only 10% of what’s produced in full breakdown of O2. Most cells rely on low levels of glycolysis.

Question 2

Sources of glucose:

Answer 2

1. Fed state -> glucose from digestion
2. Glycogen in fasting state/exercise -> muscle + liver
3. Starvation -> gluconeogenesis

Question 3

Resting muscle stores

Answer 3

Glycogen grannules

Question 4

Liver primarily uses glycogen between

Answer 4

Fed and fasting state, only lasts 48 hours

Question 5

Glycogen breakdown

Answer 5

1. Glycogen phosphorylase converts glycogen to glucose phosphate
2. Phosphoglucomtase converts glucose phosphate to glucose

Question 6

Mechanism of glycolysis

Answer 6

1. Glucose diffuses into cell via transporter using ATP
2. Hexokinase phosphorylates glucose so it can’t bind to transporter again
3. Glucose-phosphate-isomerase used to convert glucose-6-p to fructose-6-p
4. Phosphofructo-kinase converts fructose-6-p to fructose-1,6-bisP using ATP
5. Aldolase splits it into dihydroxyacetone phosphate and glyceraldehyde-3-P
6. Triose phosphate isomerase converts dihydroxyacetone phosphate into glyceraldehyde-3-P
7. Glyceraldehyde-3-P dehydrogenase converts 2 glyceraldehyde-3-P into 2 1,3-biphosphoglycerate making 2 NADH
8. Phosphoglycerate kinase converts this to 2 3-phosphoglycerate making 2 ATP
9. Phosphoglycerate mutase converts this to 2 2-phosphoglycerate
10. Enolase to 2 phosphoenolpyruvate making 2 ATP
11. Pyruvate kinase to 2 pyruvate

Question 7

Reaction by aldolase

Answer 7

reversible

Question 8

What happens when there’s too much glucose-6-P?

Answer 8

Hexokinase is inhibited

Question 9

Why is glucose-phosphate-isomerase needed?

Answer 9

Convert glucose-6-p to fructose-6-p to allow phosphorylation at C1

Question 10

What happens when NAD accepts H at glyceraldehyde-3-P

Answer 10

Oxidation of glyceraldehyde-3-P and energy is used for phosphorylation -> 1,3,

Question 11

When is ATP produced in glycolysis?

Answer 11

1. When phosphoyglycerate kinase converts 2 phosphoglycerate to 3-phosophoglycerate
2. When enolase converts 2 2-phosphoglycerate to 2 phosphoenolpyruvate

Question 12

How is NADH converted back to NAD?

Answer 12

1. NADH converted to NAD in mitochondria with O2
2. Pyruvate -> lactate with lactate dehydrogenase
3. Acetalaldehyde -> ethanol

Question 13

How can glycolysis occur at low levels of glucose in humans?

Answer 13

1. Galactose, fructose and mevinose can also be used as substrates in glucose
2. Only 1 ATP used if glucose-1-P generated from glycogen in glycolysis

Question 14

Does glycolysis only occur in anaerobic conditions?

Answer 14

No, anaerobic glycolysis quick but low efficiency -> rate is sped in anaerobic conditions. Glycolysis can be used to bring down glucose levels in blood.

Question 15

How does glycolysis occur anaerobically in humans?

Answer 15

All tissues produce lactate (RBC + white muscle) -> liver takes up lactate b/c good blood supply