Lecture 24 - Glucose as a fuel molecule #2

Question 1

What are the basic steps of Glycolysis?

Answer 1

1. Splitting of glucose (one 6 Carbon glucose to two 3 Carbon pyruvate molecules)
2. Energy is conserved in ATP and NADH
3. Pyruvate may be further metabolised aerobically or anaerobically

Question 2

What is the activation of glucose?

Answer 2

Getting the molecule into a form so energy can be captured - this requires an energy input

Question 3

What are the two phases of glycolysis?

Answer 3

1. Energy Investment phase
2. Energy Payoff phase

Question 4

What happens during the energy investment phase?

Answer 4

The molecule is split
(1X6C to 2X3C) at the
end of the investment
phase

Question 5

What happens during the energy payoff phase?

Answer 5

After a conversion,
both 3C molecules
processed in the
same way

Question 6

What is the first key reaction for the activation of glucose?

Answer 6

Glucose + phosphate ➔ glucose-6-phosphate + H2O

Question 7

Is the first key reaction for the activation of glucose energetically favourable?

Answer 7

No, has +ve ΔG, but is required for glucose to be used as a fuel molecule

Question 8

How is this non-spontaneous first key reaction for the activation of glucose carried out then?

Answer 8

By the coupling of the reaction (+ΔG) to ATP hydrolysis(-ΔG). Allowing the overall reaction to be spontaneous (-ΔG)

Question 9

What is the overall coupled reaction?

Answer 9

Glucose + ATP ➔ glucose-6-phosphate + ADP

Question 10

What is the second key reaction in the activation of glucose?

Answer 10

Glucosephosphate isomerase - rearrangement from glucose-6-phosphate into fructose-6-phosphate (F-6-P) (+ΔG)

Question 11

What is the third key reaction in activation of glucose?

Answer 11

Phosphofructokinase - 2nd activation of glucose that uses ATP hydrolysis to convert Fructose-6-phosphate into Fructose-1,6-biphosphate (FBP)

Question 12

What occurs during the splitting (aldolase) reaction?

Answer 12

Occurs after the third key step of glucose activation.

FBP is split by aldolase forming DHAP, and G-3-P

Question 13

What phase of glycolysis is G-3-P used?

Answer 13

In the energy payoff phase

Question 14

What is the consequence of G-3-P being used up in the energy payoff phase?

Answer 14

The G-3-P concentration is low which drives the reaction from DHAP to G-3-P

Question 15

What enzyme catalyses the rearrangement of DHAP into G-3-P?

Answer 15

Triose phosphate isomerase

Question 16

What is substrate level phosphorylation? (SLP)

Answer 16

The direct use of energy from a substrate molecule to drive the synthesis of ATP (or equivalent)

Question 17

What is one way to release energy to drive a SLP?

Answer 17

By the cleavage of a high-energy phosphate ester bond on a substrate

Question 18

What is NAD?

Answer 18

A coenzyme required by some enzymes that catalyse redox reactions

Question 19

What is NAD derived from ?

Answer 19

Niacin (vitamin B3)

Question 20

What are the two forms of NAD?

Answer 20

NAD+(the oxidised form)
NADH(the reduced form)

Question 21

What is the importance of oxidising G-3-P?

Answer 21

It is a reaction for making an ATP profit