Catabolism of pyruvate

Question 1

How is NAD+ derived?

Answer 1

From a vitamin called niacin

Question 2

How is NAD+ regenerated?

Answer 2

Through the oxidative metabolism of pyruvate

Question 3

What does NADH deliver to the respiratory chain?

Answer 3

Electrons

Question 4

What is NAD+

Answer 4

An electron acceptor

Question 5

What are the 3 names for stage 2?

Answer 5

Citric acid cycle
Krebs cycle
Tricarboxylic acid (TCA) cycle

Question 6

Where does the TCA cycle occur?

Answer 6

In the mitochondria -the inner membrane contains proteins for the electron transport chain, ATP synthase and transport proteins
The matrix contains the enzymes needed for the TCA cycle

Question 7

How does pyruvate enter the mitochondrial matrix?

Answer 7

It follows the H+ gradient from the cytosol to the matrix
There is a pyruvate transporter that trasports H+ and pyruvate by facilitated diffusion
There is a similar process that regulated ADP, ATP and Pi movement into and out of the cell

Question 8

What enzyme catalyses the oxidative decarboxylation of pyruvate to acetly-CoA?

Answer 8

Pyruvate dehydrogenase complex (PDC)

Question 9

How is PDC regulated?

Answer 9

Phosphorylation, it consists of 3 enzymes in a complex`

Question 10

What does PDC determine?

Answer 10

Glucose oxidation in well oxygenated tissues

Question 11

Is the reaction from pyruvate to acetly-CoA reversible?

Answer 11

No

Question 12

What reaction does PDC initiate?

Answer 12

Pyruvate loses a carbon dioxide to form HETPP

Question 13

How many reactions are in the TCA cycle?

Answer 13

Eight reactions in total

Question 14

What will acetyl Co-A bind with to form?

Answer 14

The 2 carbon acetyl Co-A will bind with a four carbon unit to form a six-carbon unit

Question 15

What reaction will this six carbon unit undergo?

Answer 15

Decarboxylation twice, forming 2 CO2 molecules

Question 16

How many oxidation reactions are there?

Answer 16

4, yielding NADH, H+ and FADH2

Question 17

In what form is energy stored?

Answer 17

One GTP is formed in the TCA cycle

Question 18

Where are all the enzymes bar one in the TCA cycle located?

Answer 18

In the mitochondrial matrix

Question 19

What enzyme is not located in the mitochindrial matrix and where is it located?

Answer 19

Succinate dehydrogenase, it is located in the inner mitochondrial membrane

Question 20

What reaction does succinate dehydrogenase do?

Answer 20

Succinate + FAD = Fumarate + FADH2

Question 21

What can all the products from stage 2 metabolism give rise to?

Answer 21

Acetyl-CoA which can be oxidised completely to form CO2

Question 22

What are all the enzymes of the TCA cycle associated with?

Answer 22

The mitochondria

Question 23

What does each turn of the TCA cycle involve?

Answer 23

The uptake of 2 carbon atoms in the form of acetyl-CoA and the release of two carbon atoms as CO2
Transfer of 3 pairs of electrons to NAD+ from NADH + H+
Transfer of 1 pair of electrons to reduce FAD to FADH2

Question 24

What does one substrate level of phosphorylation result in?

Answer 24

The formation of GTP from GDP + Pi

Question 25

How is the TCA cycle controlled?

Answer 25

The conversion of pyruvate to Acetyl-CoA, acetly-CoA to citrate, and many of the other steps in the cycle are controlled by ATP, acetyl-CoA and NADH

Question 26

What does high levels of ATP, acetyl-CoA and NADH mean?

Answer 26

There is lots of energy and so the cycle can be slowed down

Question 27

What does high levels of ADP and NAD+ mean?

Answer 27

There is a lack of energy and so the cycle needs to be sped up

Question 28

What does high levels of succinyl-CoA and acetyl-CoA mean?

Answer 28

There is plenty of precursor molecules for bio-synthetic reactions

Question 29

What is the net yield for each moleculs of glucose after the TCA cycle?

Answer 29

4 ATP
10 NADH
10 H+ 
2 FADH2
6 CO2

Question 30

What is an example of a stage 2 metabolic disorder?

Answer 30

PDC deficiency. The pyruvate dehydrogenase is an enzyme of the pyruvate dehydrogenase complex. It is located on the X chromosome. Results in neurological disease, hypotonia, respiratory problems