Energy I: Metabolism, ATP and Glycolysis

Question 1

List the processes included in the term ‘metabolism’.

Answer 1

• Synthesis of new molecules
• Establishing ion gradients
• Mechanical Work
• Keeping warm

Question 2

Where do we derive all our energy from?

Answer 2

The food we eat

Question 3

What is catabolism?

Answer 3

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

Question 4

What is anabolism?

Answer 4

Synthesis of new molecules from less complex components.

Question 5

Why must we know about Metabolism?

Answer 5

To know the metabolic basis of diseases like diabetes, atherosclerosis and gall stones. Diseased sate changes the way the body uses food - to understand disease we need to know hoe the body normally deals with nutrients. Can use changes in metabolites to aid diagnostics and to follow treatment.

Question 6

What processes in metabolism do you need to know about?

Answer 6

Glycolysis, gluconeogenesis, TCA and Urea Cycle.

Question 7

Discuss the importance of ATP.

Answer 7

ATP is central to a cell and therefore a bodies energy provision.
Can act as both an acceptor and donator of energy. It acts as a short term reservoir of energy.

Question 8

How much energy is available from the hydrolysis of ATP?

Answer 8

65kj/mole

Question 9

How much energy is used at rest?

Answer 9

40Kg/24hr

Question 10

How much energy is used during exercise?

Answer 10

0.5Kg/minute

Question 11

How much ATP does the body have?

Answer 11

Only 100g - to meet the demands of the body it must re-synthesise ATP from ADP, this is largely done through oxidative phosphorylation and this takes place in the mitochondria

Question 12

List the major oxidative pathways.

Answer 12

• Glycolysis -Citric acid cycle -Electron Transport coupled to oxidative phosphorylation
• Fatty acid oxidation

Question 13

Recite the reactants and products for glycolysis.

Answer 13

Reactants                    Products
1 Glucose                    1 Pyruvate
2NAD+                        2NADH
2ADP                           2ATP
2Pi

Question 14

What regulates glycolysis?

Answer 14

Enzymes catalysing irreversible reactions are potential sites for regualtion.
Activity of such enzymes can be regulated by - reversible binding of allosteric effectors -covalent modification -transcription

Question 15

What can glycolysis rate be measured in?

Answer 15

Milliseconds, seconds and hours

Question 16

What Enzyme catalyses the first part of glycolysis?

Answer 16

Hexokinase is the initial enzyme of glycolysis, catalyzing the phosphorylation of glucose by ATP to glucose-6-P. It is one of the rate-limiting enzymes of glycolysis. Its activity declines rapidly as normal red cells age. Helps to store glucose, is inhibited by its product G-6-P.

Question 17

What enzyme cataylses the second part of glycolysis? Stimulators/inhibitors?

Answer 17

Phosphofrucktikinase - catalyses the ATP dependent phosphorylation to convert fructose-6-phosphate into fructose 1,6 Phosphate and ADP, it’s one of the key regulating and rate limiting steps of glycolyis.

• inhibited by ATP, citrate and H+
• Stimulated by AMP

Question 18

Final enzyme used in glycolysis?

Answer 18

Pyruvate kinase - catalyses the transfer of a phosphate group from phosphoenol pyruvate to pyruvate and ATP. Inhibited by ATP (product)

Question 19

What happens in muscle s in terms of glycolysis?

Answer 19

Glycolysis is regulated to meet the need for ATP.
ADP+ADP—>ATP+AMP (catalysed by Adenylate kinase)
PFK id the most important control point - high concentrations of ATP inhibit PFK by lowering the affinity for fructose 6 phosphate. Also inhibited by low pH.

Question 20

Inhibition of PFK leads to…

Answer 20

Inhibition of hexokinase

Question 21

AMP is a signal for…

Answer 21

Low energy state

Question 22

Discuss the regulation of glycolysis in the liver?

Answer 22

-Regulation is more complex-
-High concentrations of ATP inhibit PFK
-PFK is inhibited by citrate
-PFK is stmulated by a build up of F6P
-Hexokinase is inhibited by G6P
-But the liver also had gluckinase which is not inhibited by G6P
REFER TO DIAGRAM

Question 23

Tumours and exercising muscles…

Answer 23

Use a common metabolic pathway - their energy needs are met through anaerobic respiration

Question 24

Explain how ow oxygen stimulates the expression of many glycolytic enzymes, in tumours?

Answer 24

When tumours outgrown their blood supply, oxygen delivery is reduced, tumour cell metabolism reverts to glycolysis. Reduction in oxygen leads to the acivation of transcription factor HIF-1alpha - this regulates the expression of a number of enzymes in the glycolytic pathway.

Question 25

Who ways pyruvate can be used?

Answer 25

made into lactate ( muscles) or Acetyl CoA. Look at diagram