Enzymes

Question 1

What do enzymes do

Answer 1

Affect both structure & function: they catalyse reactions that affect metabolism at a cellular and whole organism level

Question 2

Role of intracellular enzymes e.g. catalase

Answer 2

Produced inside cell
Catalase catalysed decomposition of hydrogen peroxide (which causes oxidative stress) into water & oxygen

Question 3

Role of extracellular enzymes e.g. amylase & trypsin

Answer 3

Amylase - catalyses digestion of starch to maltose in saliva / small intensive lumen
Trypsin - pancreatic endopeptidase catalyses hydrolysis of peptide bonds in small intestine lumen

Question 4

What are the two models of enzyme action

Answer 4

Induced fit model
Vs
Lock & Key hypothesis

Question 5

Lock and key hypothesis steps

Answer 5

Question 6

Induced fit model of enzyme activity

Answer 6

Question 7

Factors that affect enzyme activity

Answer 7

Effects of pH
Temperature
Enzyme concentration
Substrate concentration

Question 8

Effect on pH on enzyme activity

Answer 8

Diff enzymes = diff optimum pH conditions
pH changes affect the amino acids interactions in the chain
Making them unfold & altering the shape of the active site & the enzyme becomes denatured

Changes jn pH affect H bonds, ionic bonds & those between the amino acid variable R groups
All these bonds will act differently in diff concentrations of Hydrogen ions

This impacts the 3D shape therefore, change in reduction of RoR

Question 9

Effect of temperature on enzyme activity

Answer 9

Higher temp = the molecules move faster & collide more often

Q10 - temp co-efficient: measures how much the rate of reaction increases with a 10°C rise in temperature

If the temp is too high… denatured! Bonds holding the proteins together vibrate until the bonds strain and then break
The breaking of these bonds, change in the tertiary structure of the protein
The enzyme = denatured, the active site has changed shape and is no longer complimentary to the substrate & the enzyme can no longer function as a catalyst

Question 10

Enzyme concentration effect of enzyme activity

Answer 10

Question 11

Effect of substrate concentration on enzyme activity

Answer 11

Question 12

Effect of substrate concentration on enzyme activity

Answer 12

Question 13

What are cofactors

Answer 13

Non protein compounds required for enzyme activity
-> coenzymes
-> inorganic cofactors
-> prosthetic groups

Question 14

What are coenzymes

Answer 14

Organic Co-factors & don’t bind permanently & often transport molecules or electrons between enzymes

Question 15

What are inorganic co-factors

Answer 15

E.g. Cl-
Often metal ions
These facilitate temporary binding between substrate & enzymes

Question 16

What are prosthetic groups

Answer 16

Tightly bound cofactors act as a permanent part of enzymes binding site, e.g. Zn2+ for carbonic anhydrase

Question 17

What are enzyme inhibitors

Answer 17

Substances that slow down or stop a reaction by affecting the binding of the substrate to the enzymes
These can be reversible or irreversible

Question 18

What are irreversible inhibitors

Answer 18

E.g. heavy metal ions like mercury & silver
Cause disulphide bonds within the structure to break, causing the active site shape to change, thus affecting the protein activity

Question 19

Reversible inhibitors ?

Answer 19

Bind to the active site through the hydrogen bonds and weak ionic interactions, therefore don’t bind permanent

Question 20

What are the 2 types of reversible inhibitors

Answer 20

Competitive inhibitors
Non-competitive inhibitors

Question 21

How do competitive inhibitors act / work / what are they

Answer 21

Similar in structure to the substrate molecule: they bind to the active site of the enzyme, decreasing its activity ad they compete with substances for the enzyme

Amount of product formed = same, but rate at which product formation occurs decreases

The higher the concentration of competitive inhibitor, the lower the reaction rate

Can be reversed by increasing substrate as this out competes them

Question 22

How do non-competitive inhibitors work

Answer 22

• bind at another site on the enzyme = the allosteric site
• binding to this causes changes in the active site
  Therefore preventing the binding of the substrate
  Increasing substrate conc = no effect

Many drugs are inhibitors e.g. penicillin inhibits an enzyme