Molecules: Enzymes And Metabolism

Question 1

What is anabolism

Answer 1

Synthesis of complex molecules from simpler molecules

Requires input of energy

Question 2

What is catabolism?

Answer 2

Breakdown of complex molecules into simpler molecules (e.g. hydrolysis)

Energy is released

Question 3

Describe the structure of a catalyst

Answer 3

Active site formed by folding of polypeptide chain(s)

Resulting 3D shape forms the active site, where substrate interacts with enzyme

Question 4

What is collision theory?

Answer 4

1. Particles must collide to react
2. Must have sufficient energy to break and make new bonds
3. Must collide at the correct orientation

Question 5

What is the induced fit model?

Answer 5

Active site undergoes a slight change in shape to tighter fit the substrate (lock and key)

Enzyme then induces weakening of bonds thus reducing activation energy needed for reaction

Goes back to its original shape after releases products

Question 6

How does Denaturation destroy enzyme function?

Answer 6

Destroys tertiary/quaternary conformation of protein

Occurs due to: extreme temp, pH, heavy metal

Question 7

Activation energy and transition state

Answer 7

Activation energy is minimum amount of energy needed to reach transition state in which bonds in substrate are broken

Enzymes help lower activation energy (MODS)

Question 8

What are the 3 factors affecting enzyme concentration?

Answer 8

Temp
pH

Substrate concentration
Enzyme concentration

Question 9

What happens when pH is extreme?

Answer 9

Will alter 3D structure of its active site:

Affects charges on amino acid molecule=no more attraction between amino acids—> Denaturation

Question 10

Intracellular enzyme-catalysed reactions

Answer 10

Metabolic reactions in cell catalysed by enzymes produced by free ribosomes

Glycolysis—>cytoplasm
Krebs cycle—>mitochondria

Question 11

Extracellular enzyme-catalysed reactions

Answer 11

Outside cell, catalysed by enzymes produced by bound rbibosomes and secreted outside cell by exocytosis

Lipase, protease, amylase in gut

Question 12

Explain the generation of heat by metabolic reactions

Answer 12

2nd law thermodynamics no energy transformation is 100% efficient

Some energy is always lost in metabolic reaction and used to maintain constant body temp in warm blooded mammals

Question 13

Competitive vs non-competitive inhibition

Answer 13

Competitive: inhibitor competes w substrate to bind to active site (increase in substrate conc.=reduced inhibitor rate) chemically similar to substrate

Non-competitive: inhibitors bind to allosteric site (away from active site) altering enzyme shape, increase in conc. no effect

Question 14

Example or competitive & non-competitive inhibition

Answer 14

Statin drugs competitive lower cholesterol levels (inhibit enzyme HMG-CoA that plays role in cholesterol synthesis)

Hexokinase role in glucose metabolism. Glucose-6-phosphate a product of hexokinase activity can bind to allosteric site of hexokinate and regulate glucose metabolism in brain

Question 15

What is end-product inhibition?

Answer 15

Where end-product of reaction acts as non-competitive inhibitor (e.g. hexokinase)

Question 16

Mechanism based inhibition

Answer 16

Inhibitor binds permanently to active site—> produces stable inhibitor eb]nzyme complex= no catalytic activity

Harmful to organisms e.g. penicillin weakens cell wall of bacteria, wall bursts