Glycolysis And The Krebs Cycle

Question 1

What is the name of ATP and what is its function?

Answer 1

Adenosine triphosphate.
It is an energy carrier. The phosphate bonds are high energy and will release this energy when broken.

In simple terms:
ATP — energy used in metabolic process — ADP + Pi — energy produced in respiration — ATP…

ATP — ADP + Pi

Question 2

What do kinase enzymes do?

Answer 2

Also involved in the movement of phosphate

Question 3

Overall what does glycolysis produce?

Answer 3

1 molecule of glucose:
2 molecules of ATP
2 NADH
2 molecules of pyruvate

Question 4

What is the job of co-enzymes?

Answer 4

In many metabolic pathways they transfer electrons in oxidation and reduction reactions.
They can also go on to be used in ATP production

Question 5

What does glucose form in the first step of glycolysis?

Answer 5

Glucose — Glucose-6-phosphate

Using hexokinase in most the body and glucokinase in the liver

Question 6

What does Glucose-6-Phosphate form in the second step of glycolysis?

Answer 6

Glucose—phosphate forms Fructose -6-Phosphate
Using Phosphoglucose isomerase

Reversible reaction

Question 7

Fructose-6-phosphate forms…

Answer 7

Fructose-1,6-bisphosphate

Using phosphofructokinase-1

This is also the rate limiting step of glycolysis and hence controls the mechanism.

Question 8

What does fructose-1,6-bisphosphate form…

Answer 8

Both Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

Using enzyme adolase

Triose phosphate isomerase also converts dihydroxyacetone phosphate into glyceraldehyde-3-phosphate

Favoured as G-3-P is used up

Question 9

You now have 2 glyceraldehyde-3-phosphate molecules which produce…

Answer 9

2 (1,3-bisphosophoglycerate) and 2 NADH

Using 2pi and 2 NAD

Uses the enzyme Glyceraldeyde-3-phosphate dehydrogenase

Also reversible

Question 10

2(1,3-Bisphosophoglycerate) is converted into….

Answer 10

2(3-phosphoglycerate)
Using phosphoglycerate kinase

2 ADP— 2 ATP

Question 11

2 (3-phosphoglycerate) is converted into…

Answer 11

2 (2-phosphoglycerate)
Using phosphoglyceromutase

Reversible

Question 12

2 (2-phosphoglycerate) is converted into…

Answer 12

2 (phosphoenolpyruvate)

Using enolase and H20 is produced

Question 13

2 (phosphoenolpyruvate) is converted into…

Answer 13

2 pyruvate molecules
Using pyruvate kinase
ADP-ATP

Question 14

Overall glycolysis equation:

Answer 14

Glucose + 2NAD + 2Pi + 2ADP — 2 Pyruvate + 2 NADH + 2H + 2ATP + 2H20

Question 15

Pyruvate is converted into… during anaerobic respiration.

Answer 15

Into Lactate, using lactate dehydrogenase

Question 16

Regulators of glycolysis?

Answer 16

AMP and ATP can bind to a site away from is active site and cause the change in shape of PFK-1 (non-competitive inhibitors)

In low ATP conditions its rate increase, in high it is inhibited
In low AMP conditions its rate is inhibited, in high its increased
Citrate may also play a role in PFK-1 inhibition

Question 17

2 ADP — AMP + ATP using which enzyme?

Answer 17

Adenylate Kinase

Question 18

What are all the names for the krebs Cycle?

Answer 18

Citric acid cycle and TCA cycle

Question 19

Overview of the Krebs Cycle…

Answer 19

Pyruvate is transported into the mitochondria and converted into Acetyl-CoA (link reaction)

The Acetyl-CoA is then used in the Krebs cycle. It is added to Oxaloacetate to form citrate and the cycle continues.

Overall:
Acetyl-CoA + 3NAD + FAD + GDP + Pi + 2H20 — 2CO2 + 3NAD + FADH2 + GTP + 3H* + CoA

Question 20

What is the links reaction:

Answer 20

Pyruvate + CoA +NAD — Acetyl-CoA + CO2 + NADH + H*

Main point produces Acetyl-CoA and a NADH

Question 21

Citrate forms…

Answer 21

Isocitrate

Using aconitase

Question 22

Isocitrate forms…

Answer 22

Ketoglutarate

Using isocitrate dehydrogenase

Also forms NADH and CO2

Question 23

Ketoglutarate forms…

Answer 23

Succinyl-CoA

Using a-Ketoglutarate

Also forms NADH + H*

Question 24

Succinyl-CoA forms…

Answer 24

Succinate
Using succinyl CoA thiokinase
Also forms GTP from GDP

Question 25

Succinate is converted into…

Answer 25

Fumarate

Using succinate dehydrogenase

Question 26

Fumarate is converted into…

Answer 26

Malate

Using fumarase

Question 27

Malate is converted into…

Answer 27

Oxaloacetate
Using Malate dehydrogenase

And the cycle starts again, with a new molecule of Acetyl-CoA

Question 28

What are the three enzymes that regulate the Krebs cycle?

Answer 28

Isocitrate DH

a-Ketogluterate DH

Citrate synthase (converts Acetyl - CoA + oxaloacetate into Citrate)

Question 29

How does Isocitrate DH regulate the Krebs cycle?

Answer 29

An increase in isocitrate dehydrogenase leads to an increase in citrate synthase reaction rate increased.

Question 30

How does a-ketoglutarate DH regulate the Krebs cycle.

Answer 30

It is inhibited by its products NADH and succinyl-CoA
Also inhibited by GTP, ATP

Activated by Ca2+ - useful in generating ATP during intense muscle excerice

Question 31

How does citrate synthase regulate the Krebs cycle?

Answer 31

ATP and NADH, allosterically inhibit citrate synthase.
Hence reduces rate of reaction.

Succinyl Co-A ( a Krebs cycle product), competitively inhibits citrate synthase.
It competes for binding to the active site of citrate synthase with its substrates.