Cell Metabolism

Question 1

What is the difference in Phosphodiester bonds and Phosphoanhydride bonds?

Answer 1

A bond between a sugar group and a phosphate group

The high energy of this molecule comes from the two high-energy phosphate bonds. The bonds between phosphate molecules are called phosphoanhydride bonds. They are energy-rich and contain a ΔG of -30.5 kJ/mol.

Question 2

How many molecules of ATP are formed per molecule of glucose?

Answer 2

36-38 molecules.

38 * -31 = 1178 kJ/mol

1178 / 2872 ( combustion of glucose ) =

41% efficient

Question 3

What reaction is defined by formation of covalent bonds?

Answer 3

Ligation requiring ATP cleavage

Question 4

What type of reaction is glucose to glucose 6 phosphate?

Answer 4

Phosphate group transfer (phosphorylation)

Hexokinase required

irreversible reaction

traps glucose by means of negative charge

Question 5

What reaction does Phosphoglucose isomerase aid?

Answer 5

Glucose 6 phosphate to fructose 6 phosphate

isomerization

Question 6

Why does phosphofructokinase need to be regulated?

Answer 6

Fructose 1,6 biphosphate is created which is entered into the glycolysis pathway.

Group transfer reaction

Question 7

What hydrolytic reaction does the enzyme aldolase aid?

Answer 7

Fructose 1,6 biphosphate to G3P ( glyceraldehyde 3 phosphate) and DHAP (Dihydroxyacetone phosphate)

Both high energy compounds

hydrolytic reaction

Question 8

What does TPI stand for and what reaction does it affect?

Answer 8

It is the enzyme: Triose phosphate isomerase.

Dihydroxyacetone phosphate to glyceraldehyde 3 phosphate

isomerisation reaction

Question 9

what deficiency is the most severe form of a group of diseases known as glycolytic enzymopathies, which are rare genetic diseases that lead to the degeneration of the red blood cells.

Answer 9

Triosephosphate isomerase deficiency. most sufferers die within the first 6 years of their lives

Question 10

When is NADH first generated in glycolysis?

Answer 10

2 are formed when 2 G3Ps made into 1,3 biphosphate by G3P dehydrogenase

Redox and group transfer

Question 11

What does 1,3 biphosphate become and what enzyme is involved?

Answer 11

3-phosphoglycerate ( 3PG)

3-phosphoglycerate kinase ( creates 1 ATP)

group transfer

Question 12

What does 3 phosphaglycerate become and what enzyme is involved?

Answer 12

2-phosphoglycerate

phosphoglycerate mutase

isomerisation reaction

Question 13

What reaction is enolase involved in and why is it a dehydration/group removal reaction?

Answer 13

2-phosphoglycerate to phosphoenolpyruvate + H2O (removed)

also a group removal

Question 14

How is pyruvate created at the end of glycolysis?

Answer 14

Phosphoenolpyruvate to pyruvate through a group transfer reaction.
By pyruvate kinase, generates ATP

group transfer

Question 15

What are the net results of glycolysis?

Answer 15

2 NADHs
2 ATPs ( 4 ATP - 2 ATP)
2 pyruvates

Question 16

What uses the Alcoholic fermentation of pyruvate?

Answer 16

Yeast and can occur under anaerobic conditions

Question 17

How is Pyruvate turned into Ethanol through alcoholic fermentation?

Answer 17

Pyruvate is turned to Acetylaldehyde through pyruvate decarboxylase

Acetylaldehyde is reduced into Ethanol by alcohol dehydrogenase and NADH oxidation to NAD

Question 18

How is lactate generated by Pyruvate and why?

Answer 18

By lactate dehydrogenase and NADH oxidised to NAD+. It is a reversible reaction

Cells will produce lactate to replenish NAD+

Question 19

Why is NAD+ needed?

Answer 19

for the dehydrogenation of G3P which is the first step pf generating ATP for the body, it may become reduced as NADH formation is greater than oxidation occuring by oxidative chain for NAD

Question 20

What role does Creatine phosphate play?

Answer 20

Acts as a buffer

Can be broken down into Creatine and ATP when phosphate is in high demand.

Question 21

How is Pyruvate turned into Acetyl CoA and CO2?

Answer 21

Pyruvate reacts with HS-CoA through pyruvate dehydrogenase (PDH) and NAD reduction.

(ligation reaction)

occurs in mitochondria of cell

Question 22

What is the high Energy bond in Acetyl CoA and why is it important?

Answer 22

Thioester bond

Readily hydrolysed enabling Acetyl CoA to donate the Acetate ( 2 carbons ) to other molecules.

Question 23

How can a Vitamin B12 deficiency lead to a Beri Beri?

Answer 23

VB12 creates Thiamine which acts as a cofactor for PDH. A deficiency causes damage to peripheral nervous system, musculature weakness and decreased cardiac output.

Thiamine pyrophosphate is a cofactor of PDH complex - readily loses proton and results in carbanion attacking pyruvate

Question 24

Why is the brain vulnerable in Beri Beri?

Answer 24

It relies heavily on glucose metabolism, Need to break down pyruvate to Acetyl CoA which is compromised in Beri Beri

Question 25

What is oxidation-reduction reaction?

Answer 25

Electron transfer

Question 26

ATP hydrolysis during exercise?

Answer 26

ATP stores decrease creatine phosphate increases - all happen in 4 seconds

Anaerobic metabolism starts slowly and before aerobic metabolism which eventually overtakes it

hence why creatine used as a dietary supplement