Cell metabolism 1

Question 1

What are the stages of cell metabolism?

Answer 1

1. glycolysis
2. TCA cycle
3. Oxidative phosphorylation

Question 2

Where does glycolysis occur?

Answer 2

Cytoplasm

Question 3

Is glycolysis aerobic or anaerobic?

Answer 3

Anaerobic

Question 4

What is the net gain of ATP and NADH in glycolysis?

Answer 4

2x ATP

2X NADH

Question 5

What is the first step of glycolysis?

Answer 5

Glucose -> Glucose-6-phosphate

Enzyme: Hexokinase
ATP to ADP
Group transfer
Irreversible

Question 6

What is the second step of glycolysis? (after glucose-6-phosphate)

Answer 6

glucose-6-phosphate -> fructose-6-phosphate

Enzyme: phosphoglucose isomerase
Isomerisation

Question 7

What is the third step of glycolysis? (After fructose-6-phosphate)

Answer 7

fructose-6-phosphate -> fructose-1,6-bisphosphate

Enzyme: Phosphofructokinase
ATP to ADP
Group transfer

Question 8

What is the fourth step of glycolysis? (After fructose-1,6-bisphosphate)

Answer 8

fructose-1,6-bisphosphate -> glyceraldehyde 3-phosphate + dehydroxyacetone phosphate

Enzyme: aldolase
Hydrolytic

Question 9

Whats the 5th step of glycolysis? (After glyceraldehyde 3-phosphate + dehydroxyacetone phosphate)

Answer 9

dehydroxyacetone phosphate -> glyceraldehyde 3-phosphate

Enzyme: Triose phosphate isomerase
Isomerisation

Question 10

Whats the 6th step of glycolysis? (after glyceraldehyde 3-phosphate)

Answer 10

glyceraldehyde 3-phosphate -> 1,3- bisphosphoglycerate

Enzyme: glyceraldehye 3-phosphate dehydrogenase
Nad+ + Pi to NADH
Redox and group transfer

Question 11

Whats the 7th step of glycolysis? ( 1,3- bisphosphoglycerate)

Answer 11

1,3- bisphosphoglycerate -> 3-phosphoglycerate

Enzyme: phosphoglycerate kinase
Group transfer
ADP to ATP

Question 12

Whats the 8th step of glycolysis? (after 3-phosphoglycerate)

Answer 12

3-phosphoglycerate -> 2-phosphoglycerate

Enzyme: phosphoglycerate mutase
Isomerisation

Question 13

Whats the 9th step of glycolysis? (after 2-phosphoglycerate)

Answer 13

2-phosphoglycerate -> phosphoenolpyruvate (+H2O)

Enzyme: enolase
Dehydration reaction
Group removal

Question 14

Whats the 10th step of glycolysis? (After phosphoenolpyruvate)

Answer 14

phosphoenolpyruvate -> pyruvate

Enzyme: pyruvate kinase
ADP to ATP
Group transfer

Question 15

In what steps of glycolysis does ATP go to ADP?

Answer 15

Step 1

Step 3

Question 16

In what steps of glycolysis does ADP go to ATP?

Answer 16

Step 7 (x2)
Step 10 (x2)

Question 17

What are the 3 fates of pyruvate?

Answer 17

1. Alcohol fermentation
2. Lactate production
3. Acetyl CoA production

Question 18

What happens in alcohol fermentation?

Answer 18

`Pyruvate -> Acetaldehyde -> Ethanol

1st enzyme: pyruvate decarboxylase H+ to CO2
2nd enzyme: alcohol dehydrogenase NADH + H+ -> NAD+

Characteristic of yeast
Anaerobic
REDUCTION

Question 19

What happens in lactate production?

Answer 19

Pyruvate -> lactate

Enzyme: lactate dehydrogenase
NADH + H+ -> NAD+
Reversible
Anaerobic
Characteristic of mammalian muscle
REDUCTION

Question 20

What happens in Acetyl CoA Production?

Answer 20

Pyruvate + HS-CoA -> Acetyl CoA + CO2

Enzyme: Pyruvate dehydrogenase complex
NAD+ -> NADH
Occurs in mitochondria
OXIDATION

Question 21

How is lactate dehydrogenase used as a diagnostic tool?

Answer 21

LDH is present in many body tissues
Elevated serum levels can be used to diagnose stoke and myocardial infarction
LDH can also be used to see which patients undergoing chemotherapy for follicular lymphoma will likely undergo relapse

Question 22

What is the outcome of the TCA/Krebs cycle?

Answer 22

Each cycle produces:
2x CO2
3x NADH
1x GTP
1x FADH2
One cycle for each pyruvate

Question 23

What kind of reaction does protein metabolism require?

Answer 23

Transaminase reactions: amine group transferred from one amino acid to ketoacid forming new amino acid and ketoacid
Its a group transfer reaction

Question 24

What are the 7 molecules that all 20 amino acids can degrade into?

Answer 24

Pyruvate
Acetyl CoA
Acetoacetyl CoA
Alpha-ketogluterate
Succinyl CoA
Oxaloactate 
Fumarate

Question 25

What happens to an amino acid once its entered the TCA cycle?

Answer 25

Amino group is removed (Excreted in urea) whilst C skeleton is funnelled into glucose production or Krebs cycle

Question 26

How does glucose metabolism differ in cancer?

Answer 26

Cells can use increased expression of glucose transporters to propel tumour growth e.g. GLUT-1 We can target GLUT-1 in treatment Give patient radio labelled 18F glucose- this will accumulate in tissues with high expression of glucose transporters and can be used to locate tumour through imaging

Question 27

What are 2 ways in which electrons from NADH are transported to the mitochondrial matrix?

Answer 27

1. Glycerol-phosphate shuttle | 2. Malate- Aspartate Shuttle

Question 28

How does the glycerol-phosphate shuttle work?

Answer 28

For skeletal muscle and brain Cytosolic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to dihydroxyacetone phosphate to generate glycerol 3-phosphate Membrane bound form of same enzyme transfers electrons to FAH, these then pass on to Co-enzyme Q

Question 29

How does the maltate-aspartate shuttle work?

Answer 29

For liver, kidney and heart Also relies on cytosolic and membrane bound forms of these enzymes: Aspartate transaminase Malate dehydrogenase Transamination reaction as well as redox reaction (NAD+ to NADH)

Question 30

What is beri beri?

Answer 30

A thiamine deficiency Thiamine is a cofactor of pyruvate dehydrogenase complex Deficiency of thiamine means difficulty to make acetyl CoA Brain particularly vulnerable

Question 31

What are symptoms of beri beri?

Answer 31

damage to PNS weakness of musculature decreased cardiac output