Topic 1.4 Enzymes

Question 1

Affects the rate of collisions

Answer 1

-Temperature (kinetic energy)
-Substrate concentration
-Enzyme concentration
-Inhibitors (competitive)

Question 2

Affects the active site

Answer 2

-Temperature (denaturation)
-pH (denaturation)
-Inhibitors (non-competitive)

Question 3

Competitive inhibitors

Answer 3

-Similar shape to substrate
-Binds to active site of enzyme
-Affects collision rate

Question 4

Non-competitive inhibitors

Answer 4

-Binds to the enzyme (not active site) and changes the shape of the active site
-Binds to allosteric site
-Substrate no longer fits
-Affects active site

Question 5

How enzymes affect activation energy

Answer 5

Enzymes are catalysts because they lower the activation energy needed to drive a reaction.

Question 6

Induced fit model

Answer 6

States a substrate binds to an active site and both change shape slightly, creating an ideal fit.

Question 7

Rate equation

Answer 7

Rate= change/time

Question 8

Trypsin investingation variables

Answer 8

Milk —> amino acids (trypsin used)
-Regulate the temperature using a water
-Keep concentration of trypsin the same
-Keep the intervals regular (5° each time-then add intervals to find the optimum)
-Regulate the repeats (3 repeats for each)

Question 9

Investigating enzymes: Catalyse

Answer 9

Hydrogen peroxide —> water + oxygen (catalyse used)
-Add catalyse to hydrogens peroxide
-Use a gas syringe to collect the oxygen
-Serial dilution of the stock solution
-Repeats to find outliers and a mean

Question 10

Investigating enzymes: Amylase

Answer 10

Starch —> maltose (amylase used)
-Add buffer solution to enzymes (to regulate pH)
-Add the amylase to starch solution and add it to spotting tile at regular intervals
-Add iodine solution to test for starch- when it stops turning blue/black all the starch has reacted

Question 11

The structure of enzymes

Answer 11

Globular proteins
-Specific tertiary structure determines shape of active site, complimentary to specific substrate

Question 12

Function of enzymes

Answer 12

-Biological catalyses for intra and extracellular reactions
-Formation of enzyme substrate complexes lowers activation energy of metabolic reactions

Question 13

The induced fit model affect on enzyme action

Answer 13

-Shape of active site is not directly complimentary to substrate and is flexible
-Conformational change enables enzymes substrate complexes to form
-This puts strain on substrate bonds, lowering activation energy

Question 14

how does substrate concentration affect the rate of reaction?

Answer 14

-Enzyme concentration is fixed, so rate increases proportionally to substrate concentration
-Rate levels off when maximum number of enzyme substrate complexes form at any given time

Question 15

How does enzyme concentration affect rate of reaction?

Answer 15

-Substrate is in excess, rate increases proportionally to enzyme concentration
-Rate levels off when maximum number of enzymes,e substrate complexes form at any given time.

Question 16

How does temperature affect rate of reaction?

Answer 16

-Rate increases as kinetic energy increases and peaks at an optimum temperature
-Above optimum, ionic and H- bonds in tertiary structure break= active site no longer complimentary to substrate (denaturation).

Question 17

How does pH affect the rate of reaction?

Answer 17

-Enzymes have a narrow optimum pH range
-Outside range H+/OH- ions interact with H- bonds and ionic bonds in tertiary structure= denaturation.

Question 18

How do competitive inhibitors work?

Answer 18

Bind to active site since they have similar shape to substrate.
Temporarily prevent enzyme substrate complexes from forming until released.
-Increased substrate concentration decreases their effect.

Question 19

How do non competitive inhibitors work?

Answer 19

-Binding at allosteric binding site
-Trigger conformational change of active site
-Increasing substrate concentration has no impact on their effect

Question 20

How to work out initial rate of reaction on a graph

Answer 20

Calculate gradient of tangent at t=0

Question 21

Why is it advantageous to calculate initial rate?

Answer 21

Represents maximum rate of reaction before concentration of reactants and end-production inhibition.

Question 22

Investigating enzymes: Trypsin

Answer 22

1. Take three test tubes and measure 5cm3​ ​ ​milk​​ into each. Place in ​water bath​​ at 10°C for 5 minutes​​ to equilibrate.
2. Add 5cm​3​ ​​trypsin​​ to each test tube simultaneously and​ start the timer immediately.
3. Record how long it takes for the ​milk​​ samples to ​completely hydrolyse​​ and become ​colourless​​.
4. Repeat steps 2-3 at temperatures of ​20°C, 30°C, 40°C and 50°C​​.
5. Find the ​mean​​ time for the milk to be hydrolysed at ​each temperature​​ and use this to work out the ​rate of reaction​​.