Metabolism

Question 1

What happens and what is produced in Glycolysis?

Answer 1

• Degradation of glucose to pyruvate
• 10 enzymatic reactions involved
• 2 phases:
  1. preparation phase ( glucose to 2 biphosphate) uses 2 ATP
  2. payoff phase , 2 biphosphate to 2 pyruvate

NET: 2 ATP , 2 NADH

Question 2

What is produced in the Link reaction?

Answer 2

1 NADH from each pyruvate
1 C02 released from each pyruvate
Overall product is 1 acetyl coA from each pyruvate

Question 3

What is produced in the Krebs Cycle? (from both cycles)

Answer 3

6 NADH
2 FADH
2 GTP
4 carbon

Question 4

What is produced in oxidative phosphorylation?

Answer 4

34 ATP

Question 5

What controls glycolysis?

Answer 5

• Pyruvate kinase is inhibited by ATP and Acetyl coA
• Activated by fructose and biphosphate

Question 6

What happens during the Krebs Cycle?(mainly focussing on carbon)

Answer 6

• Acetyl CoA (2C) joined to a 4C molecule to form a 6C molecule
• In oxidation phase, 2 carbons are pulled off and sent to oxidative phosphorylation, two NADH made
• To regenerate oxaloacetate from 4C molecule, One FADH produced, One NADH and one ATP
• Amino acids are also fed into the krebs cycle at different points as seen y comparing similar structures

Question 7

What are fatty acids turned into and how?

Answer 7

Beta oxidation:
- Breaking up fatty acid chain into two carbon molecules
- Fed via acetyl CoA into the krebs cycle
- Large amount of electrons generated to create ATP
CANNOT BE MADE INTO GLUCOSE only ATP

Question 8

How does NADH feed in to the electron transport chain?

Answer 8

• Electrons are transferred from NADH and FADH to 02 producing H20
• 4 membrane protein complexes transfer electrons across themselves
• The net result is that hydrogen protons are pumped across mitochondrial membrane at complex 1,3 and 4
• Builds up proton concentration at intermembrane space
• This is released through ATP synthase allowing the hydrogen ions back thorugh itself generating ATP

Question 9

How is oxidative phosphorylation regulated?

Answer 9

• One of the key determinants is ATP levels
• High ATP levels and a high proton moving force can be inhibited by an enzyme which reduces proton flow
• When exercising and ATP is being used up this enzyme will be released so the gradient can continue

Question 10

What do uncoupling agents do?

Answer 10

• They can bind protons on one side of the membrane and move it to the opposite side where it loses the protons
• Bind a proton where H+ concnetration is highest so it dissipates the gradient
• ATP synthase has to work sm harder and generates lots of heat and cells start to boil <3

Question 11

What does it mean that metabolism is compartmentalised?

Answer 11

That different parts of the cell carry out specific parts of the metabolism pathways

Question 12

What metabolic processes occur on the cytosol?

Answer 12

• Glycolysis
• Pentose phosphate (breaks down glucose into pentose 5-phosphate used in nucleotide synthesis)
• Fatty acid synthesis

Question 13

What metabolic processes occur in the mitochondrial matrix?

Answer 13

• Krebs cycle
• Oxidative phosphorylation
• B-oxidation of fatty acids
• Ketone body formation (production of ketone bodies from fatty acids which serve as an alternate energy source)

Question 14

Give two examples that different tissues use different fuels to meet their metabolic needs

Answer 14

1. Your brain needs glucose
2. Your muscles need ATP

Question 15

What are Ketone bodies?

Answer 15

Contain ketone groups produced by fatty acids from the liver, brain uses this alongside glucose for metabolism

Question 16

Describe Metabolism in the Kidney

Answer 16

• Kidneys produce urine
• Plasma is filtered through glomerulus and water and glucose is reabsorbed in the proximal convulate tube
• Big site for gluconeogenesis

Question 17

Describe metabolism in the muscle

Answer 17

• Major fuel= glucose (preferable), fatty acids, ketone bodies
• Burst activity (anaerobic) glucose is mobilised from glycogen stores
• Aerobic activity uses fatty acids

Question 18

Describe the creatine system

Answer 18

• ATP generating using creatine kinase
• Allows rapid production of ATP if the glycogen method is taking a while
• Phosphocreatine transfers its P to ADP catalysed by creatine kinase to generate ATP

Question 19

What happens during anaerobic respiration?

Answer 19

• No Krebs Cycle or Oxidative phosphorylation
• Produce lactate, exported form muscle and goes back to liver via bloodstream
• 6 ATP are used to convert lactate back to G6P and then glucose
• This is called the cori cycle

Question 20

What happens after you have eaten a meal (fed state)?

Answer 20

• Rise in glucose, gets in to pancreatic beta cells and stimulates a rise in insulin
• Drop in glucagon
• Glycogen synthesis

Question 21

What does insulin do?

Answer 21

• Signals to Glut-4 to uptake glucose
• Any plasma membrane containing Glut4 is insulin dependent ie. the skeletal muscle
• Glut1,2,3 are insulin independent and can take up glucose on its own (brain)
• Control amino acid uptake

Question 22

What happens during the fasted state?

Answer 22

• Glucagon concentration increases
• Insulin secretion drops
• Stimulates glucose production in the liver
• Ketogenesis and gluconeogenesis
• Glycogen mobilisation

Question 23

How can fatty acids and acetyl coA work together?

Answer 23

Fatty acids from the blood can feed straight into acetyl coA in the muscle to produce energy