CHO Energy Extraction (Glycolysis)

Question 1

Summarise glycolysis (Embden-Meyerhof pathway):

Answer 1

Oxidation of glucose of glycogen that takes place in the cytoplasm of the cell. Glycolysis will produce either lactate or pyruvate. Oxidation of glucose creates a net gain of 2 ATP molecules whilst oxidation of glycogen produces 3.

Question 2

What is energy investment during glycolysis?

Answer 2

At stages 1 and 3 of glycolysis, ATP is consumed to (a) prevent glucose from diffusing out of the cell and to (b) increase the energy yield at the end of the reaction.

Question 3

Why does glucose produce a net positive of 2 ATP whilst muscle glycogen produces 3 through the same process?

Answer 3

Glucose requires one phosphate molecule (gained from reacting with ATP at stage 1) to prevent diffusion out of the cell. Glycogen, on the other hand, is already stored within the muscle cell so skips the first stage.

Question 4

How many stages are in a the glycolysis pathway?

Answer 4

10 stages

Question 5

What are the three most important glycolytic enzymes and what stages are they used in?

Answer 5

Hexokinase (Stage 1)
Phosphofructokinase (Stage 2)
Pyruvate kinase (Stage 10)

Question 6

What is the purpose of hexokinase?

Answer 6

Catalyses the reaction between glucose and ATP in the first stage of glycolysis.

Question 7

What is the purpose of phosphofructokinase?

Answer 7

Catalyses the reaction between fructose 6-phosphate and ATP, creating fructose 1,6-biphosphate to increase energy yield.

Question 8

What is the purpose of pyruvate kinase?

Answer 8

Catalyses the reaction between phosphoenolpyruvate, ADP, and H+ to produce pyruvate and ATP in stage 10.

Question 9

Which stage first produces a molecule of ATP?

Answer 9

Stage 7 - 1,3-biphosphoglycerate + ADP –> 3-phosphoglycerate + ATP

Question 10

What is the significance of phosphofructokinase in the sustainability of glycolysis?

Answer 10

Phosphofructokinase is the primary regulator for the speed of glycolysis and is sensitive to pH. As muscle acidity increases, the activity levels of the enzyme decreases, slowing glycolysis.

Question 11

What process occurs that duplicates the reactions from stage 6 onwards?

Answer 11

The six-carbon sugar (fructose 1,6-biphosphate) gets split into 2 three-carbon sugars (glyceraldehyde 3-phosphate) during stages 4 and 5.