Enzyme action

Question 1

What are enzymes

Answer 1

Biological catalysts

Question 2

3 conditions needed for enzyme catalysts

Answer 2

Substrate and enzyme must collide successfully
Energy of products must be less than substrates
Activation energy must be met

Question 3

Active site

Answer 3

Region which is similar to a substrates shape so the enzyme and substrate can bind

Question 4

What is formed when an enzyme and substrate bind together

Answer 4

Enzyme substrate complex

Question 5

Induced fit model of enzyme action

Answer 5

1) Substrate and enzyme collide in a certain way so that the substrate binds to the enzymes active site
2) Active site changes shape to fit with substrate
3) When bind, enzyme substrate complex is formed
4) Bond between molecules breaks
5) Product molecules released from active site

Question 6

Whole process of how all products are made

Answer 6

1) Lots of substrate, no product
2) Lots of empty active sites, high chance for substrates to collide with active sites
3) All active sites filled and substrate broken down into products
4) Substrate decreases as its broken down, products increase
5) Fewer substrate molecules available so more difficult to collide
6) Rate formation slows, fewer substrate molecules
7) Graph flatterns as substrate has been used up

Question 7

Effect of temperature

Answer 7

Temperature rises, thermal energy transferred to kinetic energy
Molecules move faster -> more successful collisions, producing more enzyme-substrate complexes
Denatured at around 60C

Question 8

Effect pH and why it denatures

Answer 8

Denatures = Charges on the amino acids in active site changes, affects the formation of enzyme-substrate complex
This changes shape of the active site
Bonds can also break, changing active site

Question 9

Effect of substrate concentration

Answer 9

As substrate concentration increases there are more chances of successful collisions, so more enzyme-substrate complexes form
The rate reaches a maximum as all the active sites are occupied (graph platos)

Question 10

Effect of enzyme concentration

Answer 10

Increases successful collisions, increases rate of enzyme substrate complex production
All substrate is turned into product at the same rate

Question 11

What are competitive inhibitors

Answer 11

Bind to active site

Question 12

What are non-competitive inhibitors

Answer 12

Bind to enzyme in position other than active site

Question 13

Competitive inhibitors and how they act

Answer 13

Compete with substrate for active site
Difference in concentration of substrate and inhibitor, determines effect on enzyme activity
Substrate concentration increases so effect of inhibitor decreases
Longer it will take for product to be made if greater concentration of inhibitor

Question 14

Non-competitive inhibitors and how they act

Answer 14

Attach at binding site which isn’t active site
Inhibitor alters shape of enzyme where it binds, so active site changes
Substrate can no longer fit
Enzyme cannot function
Inhibitor and substrate are not competing for same site
Concentration increases in substrate, does not decrease effect of inhibitor

Question 15

What do enzymes change in reactions

Answer 15

Lower the activation energy and catalyse the reaction

Question 16

Absolute specificity

Answer 16

Enzyme catalyses ONE reaction

Question 17

Group specificity

Answer 17

Enzyme acts on molecules having specific functional groups like phosphate, amino, methyl groups

Question 18

Linkage specificity

Answer 18

Enzyme acts on a specific type of chemical bond regardless the remaining molecular structure

Question 19

Stereochemical specificity

Answer 19

Enzyme acts on a certain optical or steric isomer

Question 20

How is specificity attained

Answer 20

When the substrate interacts weakly with the enzyme’s active site to form a bond
Producing covalent bonds that the enzyme can only catalyse

Question 21

What do enzymes catalyse

Answer 21

Wide range of intercellular and extracellular reactions
Determining structures and functions of a whole organism

Question 22

What two things can you measure enzyme activity (practical)

Answer 22

Measure rate of formation of a product using catalase
Measuring rate of diappearance of substrate using amylase

Question 23

What is measured for the investigation of amylase activity using iodine

Answer 23

Take samples from reaction mixture at each time interval and adding each sample to iodine in potassium iodide solution
Starch = blue-black
No starch = yellow-brown

Question 24

Why use amylase-starch solution

Answer 24

Amylase = digestive enzyme that hydrolyses starch into maltose and glucose

Question 25

Method

Answer 25

1) Place single drops of iodine solution in rows on tile
2) Label test tube with pH to be tested
3) Use syringe to place 2cm^3 of amylase in test tube
4) Add 1cm^3 of buffer to test tube using syringe
5) Add 2cm^3 using different test tube of starch solution to amylase and buffer solution, start stopwatch whilst mixing using pipette
6) At 10 secs, use pipette and place on e drop of mixture on first drop of iodine (should turn blue black)
7) Wait another 10 secs and place another drop of mixture on second drop of iodine
8) Repeat every 10 secs
9) Repeat at different pH values
Less time iodine solution takes to remain orange-brown, quicker starch has been digested , better enzyme works at that pH