Carbohydrates 3

Question 1

What is glycolysis?

Answer 1

Biochemical reaction, not involving oxygen, that splits carbohydrates into pyruvic or lactic acid whilst producing ATP

Question 2

What kind of phosphorylation does glyclysis produce ATP through?

Answer 2

Substrate level phosphorylation

Question 3

What is the only way that energy can be made when O₂ is not present?

Answer 3

Substrate level phosphorylation

Question 4

Why is glycolysis often the process used to generate energy initially during exercise?

Answer 4

O₂ cannot get to the cells quick enough

Question 5

What are the 2 phases of glycolysis?

Answer 5

Preparation phase

Payoff phase

Question 6

What happens during the preparative phase of glycolysis?

Answer 6

Two molecules of glucose-3-phosphate are produced per molecule of glucose

Question 7

What happens during the payoff phase of glycolysis?

Answer 7

ATP is produced

Question 8

What is the net gain of ATP in glycolysis and how is this distributed between the preparative and payoff phases?

Answer 8

2 ATP is used during the preparative phase and 4 ATP is gained during the payoff phase

Net gain of 2 ATP per molecule of glucose

Question 9

How many steps are there in glycolysis?

Answer 9

10

Question 10

How many of the 10 glycolysis steps are irreversible?

Answer 10

3

Question 11

Why are the irreversible steps of glycolysis irreversible?

Answer 11

Delta G during those reactions is to highly negative, too much energy put be required to reverse the reaction

Question 12

What are the 10 steps of glycolysis?

Answer 12

1. Phosphorylation of glucose (glucose → glucose-6-phosphate)
2. Conversion of G-6-P to F-6-P
3. Phosphorylation of F-6-P to F-1,6-bisP
4. Cleavege to F-1,6-bisP
5. Interconversion of triose sugars
6. Oxidation of glyceraldehyde-3-phosphate (G-3-P) to 1,3-bisphosphoglycerate (1,3-bisPG)
7. P transfer from 1,3-bisPG to ADP
8. Conversion of 3-PG to 2-PG
9. Dehydrogenase of 2-PG to phosphoenolpyruvate (PEP)
10. Transfer of P from PEP to ADP, producing pyruvate

Question 13

What is fructose-1,6-bisP broken down to into step 4 of glycolysis?

Answer 13

Glyceraldehyde-3-P or dihydroxyacetone-P

Question 14

What are the 3 irreversible steps of glycolysis?

Answer 14

Step 1 - Phosphorylation of glucose (glucose → glucose-6-phosphate)

Step 3 - Phosphorylation of F-6-P to F-1,6-bisP

Step 10 - Transfer of P from PEP to ADP, producing pyruvate

Question 15

Why is glucose converted to fructose in step 3?

Answer 15

This lowers the activation energy to proceed due to the negative charges of fructose repelling each other

Question 16

What is the first commited step of glycolysis?

Answer 16

Phosphorylation of F-6-P to F-1,6-bisP because previous intermediates can be used for other pathways but F-1,6bisP is destined for glycolysis

Question 17

What is a difference in the requirments of substrate level phosphorylation compared to oxidative phosphorylation, in terms of enzymes?

Answer 17

Substrate level phosphorylation requires soluble enzymes and chemical intermediates, whereas oxidative phosphorylation involves membrane bound enzymes and gradients of protons

Question 18

What does a diagram of glycolysis look like?

Question 19

Why does NAD⁺ need to be regenerated?

Answer 19

It is limited in the cell

Question 20

Where does NAD⁺ come from?

Answer 20

Niacin which is an essential vitamin

Question 21

What do all fates of pyruvate do?

Answer 21

Regenerate NAD⁺ to replinish what was used during glycolysis

Question 22

What is redox balance?

Answer 22

The replinishment of NAD⁺ after glycolysis

Question 23

What are the 3 pathways that pyruvate can take?

Answer 23

Fermentation in yeast to ethanol

Aerobic respiration to CO₂

Fermentation in vigorously contracting muscle cells to lactate

Question 24

What does the reaction of yeast producing ethanol look like?

Question 25

How much pyruvate is produced per molecule of glucose?

Answer 25

2

Question 26

How much lactate can be produced per molecule of pyruvate?

Answer 26

1

Question 27

How much acetyl coenzyme A can be produced per molecule of pyruvate?

Answer 27

1

Question 28

What does pyruvate becoming in the absence of oxygen?

Answer 28

Lactate

Question 29

What does the reaction of pyruvate to lactate look like?

Question 30

What is the Cori cycle?

Answer 30

Metabolic pathway where lactate is produced by anaerobic glycolysis

Question 31

What happens if we exercise vigorously?

Answer 31

Muscles don’t recieve O₂ fast enough to make ATP by oxidative phosphorylation, instead using substrate level phosphorylation producing lactate

Question 32

What is the fate of lactate that is produced from pyruvate?

Answer 32

Transfered to the liver and converted to glucose through gluconeogenisis

Question 33

Where does glycolysis happen?

Answer 33

In a cells cytoplasm

Question 34

What happens to pyruvate when cells have access to O₂?

Answer 34

Oxidised to form acetyl coenzyme A

Question 35

Where does the reaction of pyruvate to acetyl coenzyme A take place?

Answer 35

In the mitochondria of cells

Question 36

Why can red blood cells only do glycolysis (substrate level phosphorylation)?

Answer 36

They do not have any mitochondria to do oxidative level phosphorylation

Question 37

What is also formed when pyruvate is converted into acetyl coenzyme A?

Answer 37

NADH which later gives up its hydride ion (H^-) in the electron transport chain

Question 38

What does the reaction of pyruvate to acetyl conenzyme A look like?