Biochemistry

Question 1

Enzyme lock and key model

Answer 1

1. Enzyme is like a lock, active site is like a keyhole. The active site only fits certain molecules.
2. The substrate fits into the active site and forms an enzyme-substrate complex.
3. The enzyme catalyses a chemical reaction, and products are released.

Question 2

Enzyme induced fit model

Answer 2

Active site and substrate don’t fit perfectly. Substrate is flexible and binds to the active site, changing the enzymes shape.

Question 3

GLYCOLYSIS (FED)

Answer 3

1. Glycolysis is the oxidation of glucose and occurs in the cell cytosol.
2. It converts 1 glucose molecule into 2 molecules of pyruvate.
3. These pyruvate molecules can EITHER:
   -go into the mitochondria to be converted into 6 Carbon dioxides and 6 H2Os (aerobic glycolysis)
   OR
   -be converted to lactate (anaerobic glycolysis)
4. Each glucose molecule entering glycolysis results in the production of ATP and NADH.
5. Pyruvate is converted into Acetyl Coenzyme A in the matrix, which enters the KREBS CYCLE.
6. Products are NADH, ATP and PYRUVATE OR ACETYL COENZYME A.

Question 4

KREBS CYCLE (FED)

Answer 4

1. Acetyl CoA enters the krebs cycle and combines with Oxaloacetate to form citrate. 2 CO2 molecules are released.
2. Reactions with the citrate occur and release high-energy electrons.
3. FADH2 and NADH feeds electrons to the electron transport system.
4. Oxaloacetate regenerates for the next Acetyl CoA molecule.
5. Products are NADH, CO2 and ATP

Question 5

ELECTRON TRANSPORT CHAIN

Answer 5

1. Electrons enter this and are transferred to oxygen and energy is released.
2. This energy pumps Hydrogen ions at 3 complexes that pump into the intermembrane space. 3 hydrogen ions are pumped per pair of electrons.
3. This creates a concentration gradient of hydrogen across the mitochondrial matrix to generate ATP.

Question 6

Gluconeogenesis (unfed state)/anabolic

Answer 6

-Conversion of lactate and pyruvate to glucose by the liver.
1. Blood glucose drops and the pancreas releases glucagon.
2. This stimulates the breakdown of glycogen to glucose, which is released into blood.
3. Glucagon also stimulates gluconeogenesis and the breakdown of triglycerides in fat tissue.
(Muscle stores glycogen)

Question 7

Beta Oxidation (unfed state)/catabolic

Answer 7

-Process in the mitochondrial matrix that breaks down fatty acids 2 carbon atoms at a time to yield Acetyl CoA molecules.
1. Glucagon activates a lipase enzyme that releases free fatty acids and glycerol from adipose tissue
2. In the liver, beta oxidation turns the fatty aids into Acetyl CoA, and this can be converted into ketone bodies

Question 8

Catabolism vs Anabolism

Answer 8

Catabolism breaks down complex molecules and yields energy.
Anabolism synthesizes biomolecules from simpler molecules and requires energy

Question 9

Urea cycle

Answer 9

-Occurs in liver
-Converts ammonia to urea, which is excreted in urine.
-Essential for removing toxic ammonia produced from amino acid breakdown.
-Also the main source of arginine production in the body which is involved in immune function and wound healing.

Question 10

Effects of glucagon on metabolism

Answer 10

Glucagon promotes gluconeogenesis, glycogenolysis and lipolysis. It also facilitates Beta-oxidation of fatty acids and ketone body synthesis.

Question 11

Effect of insulin on metabolism

Answer 11

Insulin promotes the uptake of glucose into cells. It also stimulates glycolysis, fatty acid synthesis and triglyceride synthesis. It enhances protein synthesis. Blood glucose is also regulated by insulin.