Energy I

Question 1

Why do we need energy

Answer 1

Metabolism

1. Synthesis of new molecules
2. Establishing ion gradients
3. Mechanical work
4. keeping warm

Question 2

Define catabolism

Answer 2

The breakdown of complex molecules to release energy to carry out mechanical work

Question 3

Catabolism pathway

Answer 3

Carbohydrates, fats proteins > degradation > heat

02 to CO2

Question 4

Anabolism

Answer 4

Synthesis of new molecules from less complex compounds

Question 5

Anabolism pathway

Answer 5

Amino acids, nucleotides, sugars and fats > biosynthesis > new cells

Question 6

What does ATP do

Answer 6

Acs as both an acceptor and donator of energy

It acts a short term reservoir of energy

Question 7

What are the major oxidative pathways

Answer 7

1. Glycolysis
2. Citric acid cycle
3. Electron transport coupled to oxidative phosphorylation
4. Fatty acid oxidation

Question 8

Glycolysis pathway

Answer 8

1. Glucose is phosphorylated into glucose-6-phosphate using 1 ATP
2. Which is then isomerised into fructose-6-phosphate
3. This is then phosphorylated into fructose 1,6 bisphosphate using 1 ATP
4. This splits into two 3 carbon molecules; dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
5. These molecules are made into phosphoenol pyruvate as NAD+ and Pi are made into NADH and one ATP is generated from ADP and Pi
6. This is then made into pyruvate as 1 ATP is generated again

Question 9

What are the overall net gain of glycolysis

Answer 9

• 2 ATP molecules

- 2 NADH molecules

Question 10

Where can glycolysis be regulated and how

Answer 10

Where there are enzymes catalysing irreversible reactions

Question 11

How are these enzymes regulated

Answer 11

1. Reversible binding of allosteric effectors
2. Covalent modification
3. transcription

Question 12

What are the 3 regulatory kinases used and how they regulated

Answer 12

1. Hexokinase - Regulated by its product, G-P-6
2. Phosphate-fructokinase - Regulated by ATP, citrate and H+ and stimulated by F26BP and AMP
3. Pyruvate kinase - regulated by ATP

Question 13

How is PFK (phosphate-fructokinase) inhibited

Answer 13

High concentrations of ATP inhibit PFK by lowering the affinity for its substrate fructose-6-phosphate
Its also inhibited by low pH
Inhibition of PF leads to inhibition of hexokinase because of the backup of substrates

Question 14

What are the differences between hexokinase and glucokinase

Answer 14

1. Glucokinase has a higher Km so its only really active at high glucose concentrations
2. Hexokinase is inhibited by G-P-6 but glucokinase isn’t
3. Glucokinase is induced by insulin

Question 15

How are tumours and exercising muscles similar

Answer 15

Both rely on anaerobic respiration for the generation of ATP

Question 16

What is a limiting factor of anaerobic respiration

Answer 16

NAD+ since it limits the production of pyruvate

Question 17

How is NAD+ resynthesised

Answer 17

Lactate is made from pyruvate so NADH is metabolised back into NAD+

Question 18

Why does muscle fatigue and how does it counteract it

Answer 18

Lactate is highly acidic because of H+ ion production
Low pH is an inhibitor of glycolysis
The muscle overcomes this by exporting lactate back to the liver, here it is metabolise back to glucose

Question 19

Why do tumours use glycolysis

Answer 19

When tumours outgrown their blood supply, oxygen delivery is reduced and therefore tumour cell metabolism reverts to glycolysis

Question 20

How does tumour physiology change to accommodate glycolysis

Answer 20

A reduction in O2 leads to he activation of the transcription factor HIF-1 alpha
HIF-1 alpha regulates the expression of a number of enzymes in the glycolytic pathway such as hexokinase and phosphate-fructokinase
HIF-1 alpha also leads to blood vessel growth