Carbohydrates 3

Question 1

Define glycolysis

Answer 1

A series of cellular reactions, not requirin oxygen, that splits glucose, glycogen or other carbohydrates into pyruvic or lactic acid while storing energy in ATP molecules.

Question 2

Why is glycolysis important?

Answer 2

Its the only way ATP can be made when lacking oxygen (e.g. during strenuous exercise) or in cells lacking mitochondria (RBCs)

Question 3

How many stages/steps are involed in glycolysis?

Answer 3

2 stages
The preparatory phase has 5 steps
The payoff phase has 5 steps

Question 4

Why cant glycolysis be easily reversed?

Answer 4

It has an overall -delta G making it spontaneous and thermodynamically impossible to reverse. This applies mainly to 3 steps that are very spontaneous.

Question 5

What happens overall in the preparatory phase?

Answer 5

Glucose is converted to two Glucose-3-phosphates at the cost of 2 ATP

Question 6

What occurs in step one of the preparatory phase?

Answer 6

Glc is converted to G-6-P by hexokinase at the cost of 1 ATP

Question 7

What occurs in step 3 of the preparatory phase?

Answer 7

F-6-P is phosphorylated to F-1,6-bisP by phosphofructokinase-1 (PFK-1) at the cost of 1 ATP

Question 8

Why is Step 3 of the preparatory phase especially importnat?

Answer 8

It is the first commited step of glycoslysis because it has a very -deltaG so is irreversible.

Question 9

What happens overall in the payoff phase?

Answer 9

Two G-3-P molecules are converted to two pyruvates. This produces 4 ATP and 2 NADH.

Question 10

What occurs at step 6 of glycolysis (step one of payoff phase)?

Answer 10

Two G-3-P are converted to 1,3-Bisphosphoglycerate (1,3-bisPG) producing two NADH

Question 11

What happens in step 7?

Answer 11

Phosphate is transfered form the two 1,3-bisPG molecules to ADP to form two ATP and 3-phosphoglycerate

Question 12

What occurs in step 10?

Answer 12

Phosphate transferred from two PEP to ADP to form two ATP and two Pyruvate.

Question 13

What is different between substrate level and respiration-linked phosphorylation?

Answer 13

Substrate level phosphorylation needs soluble enzymes and chemical intermediates
Respiration linked phosphorylation requires membrane bound enzymes, oxygen and gradients of protons.

Question 14

How is NAD+ replenished?

Answer 14

By converting pyruvate to Lactace (or other intermediates e.g. ethanol & CO2) which has a by-product of using up NADH.

Question 15

What term is used to describe the constant use and replenishment of NAD+?

Answer 15

A redox Balance

Question 16

How is pyruvate converted to Lactate?

Answer 16

By Fermentation involving oxidation of NADH using Lactate Dehydrogenase

Question 17

What is the Cori Cycle?

Answer 17

The cori cycle is the process for the conversion of glucose to lactate durin glycolysis and back again. I.e. the liver is repaying the muscles oxygen debt,

Question 18

Where does the Cori cycle occur?

Answer 18

In the muscle and liver

Question 19

What two pathways make up the Cori Cycle?

Answer 19

Glycolysis and Gluconeogenisis

Question 20

When happens to pyruvate under aerobic conditions?

Answer 20

It is converted to Acetyl-CoA and fed into the Citric acid cycle (CAC)

Question 21

How is pyruvate converted to Acetyl-CoA?

Answer 21

It is moved to the mitochondria and is reacted with CoA-SH to form Acetyl-CoA and CO2. This also involves the reduction of NAD+.

Question 22

What enzyme catalyses the conversion of pyruvate to acetyl-CoA?

Answer 22

Pyruvate dehydrogenase.