26. Energy I: Metabolism, ATP, Glycolysis

Question 1

Describe Metabolism? (3pts)

Answer 1

1. Energy is derived from the food we eat.
2. We use this energy for:
3. The synthesis of new molecules
4. Establishing ion gradients
5. Perform mechanical work
6. Keep warm
7. Metabolism is the sum of catabolic processes and anabolic processes.

Question 2

What are catabolic processes?

Answer 2

The breakdown of complex molecules to release energy

Question 3

What are anabolic processes?

Answer 3

Synthesis of new molecules from less complex components.

Question 4

What is Glycolysis?

Answer 4

Glucose to Pyruvate

Question 5

Describe Catabolic processes and anabolic processes?

Answer 5

1. Large complexes such as carbohydrates, fats and proteins are ingested from the diet.
2. These are then broken down to form heat, C02 and ATP.
3. They produce precursors which are then used in anabolic processes to synthesise more complex molecules.
4. These are then used for physiological processes such as growth, repair, cell movement an d to synthesise new movement.

Question 5

Describe Catabolic processes and anabolic processes? (4pts)

Answer 5

1. Large complexes such as carbohydrates, fats and proteins are ingested from the diet.
2. These are then broken down to form heat, C02 and ATP.
3. They produce precursors which are then used in anabolic processes to synthesise more complex molecules.
4. These are then used for physiological processes such as growth, repair, cell movement an d to synthesise new movement.

Question 6

Describe ATP? (5pts)

Answer 6

1. The total amount of energy available from the hydrolysis of ATP is 65 kj/mole.
2. We use 40kg/24 hour.
3. During exercise we use 0.5 kg/minute,
4. The body has 100g ATP content. To meet the demands of the body it must re-synthesise ATP from ADP.
5. Hydrolysis of ATP drives an otherwise unfavourable reaction.

Question 7

What are the co-factors central to metabolism? (2pts)

Answer 7

1. NAD
2. FAD

• NAD is the oxidised form which is converted to NADH + H+ which is the reduced form.
• FAD+ is the oxidised form which is converted to FADH2 which is the reduced form.

Question 8

Descrribe the process of Glycolysis? (9pts)

Answer 8

1. The phosphorylation of glucose occurs to form glucose-6-phosphate catalysed by the enzyme hexokinase.
2. This energy requiring processes results in the hydrolysis of ATP to form ADP.
3. Glucose-6-Phopshate maintains the glucose gradient and traps the glucose within the cell which means the glucose-6-phosphate is unable to be transported out of cells.
4. The Glucose-6-phosphate is converted to Fructose 6 Phopshate catalysed by the enzyme Phospho-fructokinase.
5. The fructose 6 phosphate is further phosphorylated to form Fructose 1,6 Bisphophate.
6. Fructose 1,6 bisphosphate is spit into 2 3 carbon units- Dihydroxyaceton phosphate and Glyceraledhyde 3 Phosphate.
7. Glyceraldehydge 3 undergoes a series of reactions to form Phosphoenl pryuvate.
8. NADH and ATP is formed.
9. The phosphonel pryuvate is converted into Pryuvate (C3) catalysed by the enzyme pyruvate kinase.

Question 9

What are the reactants of Glycolysis? (4pts)

Answer 9

1. 1 Glucose
2. 2 NAD+
3. 2 ADP
4. 2 Pi

Question 10

What are the products of Glycolysis? (3pts)

Answer 10

1. 2 Pyruvate
2. 2 NADH
3. 2 ATP

Question 11

Describe Glycolysis regulation? (2pts)

Answer 11

1. Enzymes regulate glycolysis
2. Activity of enzymes is regulated by:
3. Reversible binding of allosteric effectors.
4. Covalent modification
5. Transcription.

Question 12

How is Hexokinse regulated? (2pts)

Answer 12

1. Regulates the conversion of glucose to glucose-6-phosphate
2. Regulated by Glucose-6-phosphate which inhibits further conversion of glucose to glucose-6-phosphate.

Question 13

How is Phospho-fructokinase regulated? (3pts)

Answer 13

1. Negatively regulated by ATP, Citrate ions, Hydrogen ions.
2. Hydrogen ions prevents the skeletal muscle cells being damaged by the low PH of continued glycolysis.
3. AMP is a positive regulator of glycolysis which is an indicator of the energetic state.

Question 14

How is Pryuvate kinase regulated? (2pts)

Answer 14

1. Pryuvate kinase in the liver is assoterically regulated by ATP.
2. Occurs only in the liver

Question 15

How is glycolysis regulated in the muscles to meet the need for ATP? (5pts)

Answer 15

1. AMP is produced when there is high amounts of ADP.
2. 2 molecules of ADP combine to form ATP and AMP catalysed by the enzyme adenylate kinase.

ADP+ ADP - ATP + AMP
- adenylate kinase

3. High concentrations of ATP inhibit PFP by lowering the affinity for Frucotse 6 phopshate.
4. Pathway is inhibited by low PH
5. Inhibition off PFK leads to inhibition of hexokinase.

Question 16

How does the regulation of glycolysis in the liver reflect its diverse function? (4pts)

Answer 16

1. High concentration of ATP inhibits PFK
2. PFK is inhibited by citrate
3. PFK is stimulated indirectly by a build up of F6P
4. Hexokinase is inhibited by G6P but the liver also has glucokinase which is not inhibited by G6P.

Question 17

Describe glycolysis in excersizing muscles? (5pts)

Answer 17

1. The formation of Pyruvate allows the generation of ATP.
2. There is a limit to the amount of glycolysis that takes place which depends on the concentration of NAD which is available in the cell.
3. Glycolysis is anaerobic in heavily exercising muscles.
4. The limitations of the muscles to generate ATP is dependant on the availability of NADH. The muscles can overcome this limitation by producing lactic acid via Pyruvate leading to the generation of NAD allowing the glycolysis reaction to continue,
5. The build of lactic acid leads to a drop in PH.

Question 18

Describe tumours? (4pts)

Answer 18

1. As the size of the tumour increases the need for the blood supply in the tumour increases.
2. This causes angionetic factors to stimulate the endothelial cells of the nearby vessels to profilerate and migrate.
3. This leads to the formation of a vascular network.
4. The rate at which a tumour grows outstrips the ability of the newly formed vessels to deliver sufficient oxygen to the tissue.
   - cells are kept in a hypoxic state to the reliance on anaerobic respiration for the energy need is apparent.

Question 19

How does low oxygen stimulate the expression of glycolytic enzymes? (3pts)

Answer 19

1. When tumours outgrew their blood supply oxygen delivery is reduced and tumour cell metabolsim reverts to glycolysis.
2. A reduction in 02 leads to the activation of the transcription factor HIF-1s.
3. HIF-1a regulates the expression of a number of enzymes in the glycolytic pathway.