2.5 Enzymes

Question 1

Define enzymes

Answer 1

ENZYMES: globular proteins which act as biological catalysts by lowering the activation energy

Enzyme-substrate specificity in active site

Question 2

Stages of enzyme catalysis

Answer 2

1. Molecular motion - collision of enzyme and substrate
2. Substrate binding to active site
3. Subtrates are converted into products by catalysed reactions
4. Products separate from active site, enzyme - unchanged - able to bind another substrate

Question 3

Role of water in catalysis

Answer 3

Substrates and enzymes dissolved in water - continous motion - successful collisions

Question 4

Factors which influence enzyme activity

Answer 4

1. Temperature: higher temp - higher kinetic E - molecules move faster - more collisions but optimum temperature - beyond that enzymes denature
2. pH: optimum pH, if active range is disrupted - denaturation
3. Substrate/enzyme concentration: if conc increases - number of collisions increase - certain conc when enzymes are fully saturated - rate will not increase

Question 5

Immobilised enzymes

Answer 5

Immobilisation: attachment of enzyme into aggregation, movement restricted (glass surf, alginate gel, bonding together)

Areas of use:

• medicine
• food industry (lactose)
• biofuels
• diagnostics
• biotech

Advantages fo immobilisation:

• separated from reaction products
• increased stability
• can be recycled - no contamination
• higher enzyme conc created - higher rate

Question 6

Digestion of starch

Answer 6

Starch digested by amylase (breaking glycosidic bonds - H2O used - hydrolysis) into maltose -> maltase -> alfa glucose

Amylase: in mouth, pancreas

Maltase: in small intestine

Question 7

Lactose intolerance

Answer 7

Production of lactase decreases with age - lactose undigested - bacteria break it - gas produced - bloating, cramps, diarrhea

Question 8

Lactose-free dairy products

Answer 8

1. Lactase obtained from yeast
2. Extract lactase, purify - immobilised - lactose broken down into glucose and galactose

Advanatges:

• lactose intolerant can drink without side effects
• monomers are sweeter - no added sugar
• lactose crystalises in ice cream production - smoother ice cream without lactose
• bacteria/yeast ferment monomers faster - faster production of youghurts/cheese

Question 9

Temperature - enzyme activity graph

Answer 9