chapter 5 enzymes

Question 1

what are enzymes

Answer 1

biological catalysts made out of mostly protein

Question 2

what the properties of enzymes? (6)

Answer 2

1. speed up chemical reactions by lowering the activation energy of the reaction
2. remain chemically unchanged at the end of the reaction (leading to point 4)
3. highly specific in actions
4. required in minute amounts
5. have an optimum temperature
6. have an optimum pH level

Question 3

what is the lock and key hypothesis?

Answer 3

enzyme: lock/ substrate: key

active site of enzyme has unique 3D shape

1. active site of enzyme is complementary to substrate
2. substrate will fit into active site of enzyme
3. substrate is attached to enzyme (enzyme-substrate complex)
4. chemical reaction occurs substrate converted to products
5. products released from active site

Question 4

how does ph or temp affect enzyme activity?

Answer 4

extreme changes in pH level causes denaturation

temperature beyond optimum temperature causes denaturation

Question 5

what is denaturation

Answer 5

Denaturation (enzyme): alters shape of active site = substrate cannot fit into active site - cannot form enzyme substrate complex = no enzyme reaction

Denaturation is irreversible

Question 6

how does low temperature affect enzyme activity

Answer 6

enzyme is inactive
kinetic energy of enzymes and substrates are low
rate of effective collisions (REC) between enzymes and substrates is low
rate of formation of enzyme-substrate complex (ESC) is low
rate of enzyme activity (REA) is low

Question 7

how does increasing temperature affect enzyme activity

Answer 7

Increasing temperature = the enzymes are more active
kinetic energy in the enzymes and substrates increases
rate of effective collisions between enzymes and substrates increases
rate of formation of enzyme-substrate complex increases
rate of enzyme activity increases.

Question 8

how does optimum temperature affect enzyme activity

Answer 8

optimum temperature = enzymes are the most active
kinetic energy in the enzymes and substrates are high
rate of effective collisions between enzymes and substrates is highest
rate of formation of enzyme-substrate complex is the highest
rate of enzyme activity highest

Question 9

how does temperature beyond optimum temperature enzyme activity

Answer 9

beyond optimum temperatures = enzymes are denatured
3D active sites of enzymes are altered
substrates can no longer fit into the active sites of enzymes
NO formation of enzyme-substrate complex
enzyme activity decreases sharply

Question 10

how does extreme changes in pH level affect enzyme activity

Answer 10

below/beyond optimum pH level: enzymes are denatured
3D active sites of enzymes are altered
substrates can no longer fit into the active sites of enzymes
NO formation of enzyme-substrate complex
enzyme activity decreases sharply

Question 11

what are limiting factors

Answer 11

factors that affect the rate at which a chemical reaction occurs when their quantity is changed
more the value of the LF, the higher the rate of chemical reaction

Question 12

what are limiting factors of enzymes

Answer 12

substrate concentration, enzyme concentration, temperature, pH

Question 13

what happens when substrate concentration is in excess?

Answer 13

substrate is in excess/substrate concentration no longer LF
enzymes are saturated
rate of ESC formed per unit time remains the same
rate of reaction is constant (plateaus) even when substrate conc increases (rxn further down x axis)

Question 14

what reactions do enzymes catalyse?

Answer 14

digestion: food molecules are too large and insoluble in water = cannot diffuse through cell membrane - digestive enzymes break down food molecules into simpler smaller substances - small enough to diffuse through cell membrane and soluble in water
-> anabolic reactions: build up complex substances (eg amino acids to protein)
-> catabolic reactions: break down complex substances (eg digestion)
-> metabolic reactions: chemical reactions that occur in an organism (eg food into energy)