ENZYMES

Question 1

Enzyme.

Answer 1

• Biological catalyst.
• Protein.
• Lowers activation energy needed for a reaction, speeding it up.
• Not used up itself.

Question 2

Catabolic reactions.

Answer 2

• Break down.
• Substrate in active site is under strain and requires less energy to break down.

Question 3

Anabolic reactions.

Answer 3

• Build up.
• Both substrates in active site and can overcome repulsions from like charges on molecules.

Question 4

Lock and key model.

Answer 4

• Enzyme has a complementary active site to substrate molecule.
• Substrate and enzyme bind forming enzyme-substrate complex.
• Enzyme breaks down substrate into products.

Question 5

Induced fit hypothesis.

Answer 5

• Active site isn’t perfectly complementary to substrates.
• Interactions of charges in active site and substrate cause AS to become more complementary to substrate.
• Form e-s complex and breaks substrate into products.

Question 6

Effect of temperature.

Answer 6

• Enzyme denatures.
• Enzymes kinetic energy increases causing more vibrations which break the bonds in the tertiary structure which changes the 3d shape of the active site.
• Not complementary to substrate.

Question 7

Effect of pH.

Answer 7

• Enzyme denatures.
• Increases/ decreases hydrogen ion concentration which can cause more repulsion/ attraction of hydrogen and ionic bonds which make up the tertiary structure therefore structure changes, changing 3d shape of active site.

Question 8

Temperature coefficient (Q10).

Answer 8

• As temp increases by 10 degrees Celsius the rate would increase by a factor of …

Question 9

Effect of enzyme/ substrate conc.

Answer 9

• As e/s concentration increases, rate increases until plateau, as there was more e/s molecules and more collisions and more complexes formed until all as full/ no more substrates to fill as therefore no more reactions.

Question 10

Inhibitors definition.

Answer 10

• A substance that stops an enzyme from catalysing a reaction.

Question 11

Competitive inhibitors.

Answer 11

• Similar shape to substrate molecule so can bind to active site of enzyme stopping reaction.
• More inhibitors = lower rate of reaction.
• Can be reversed by increasing amount of substrates.

Question 12

Non- competitive inhibitors. - Permanently binding to active site.

Answer 12

• Can bind permanently to active site and permanently block substrate to enzyme.
• Irreversible.

Question 13

Non- competitive inhibitor. - Different part.

Answer 13

• Bind to allosteric site, changes tertiary structure by disrupting hydrogen and ionic bonds, changes 3d shape of active site, substrate can no longer fit.
• Can be reversible or irreversible (if it permanently changes).

Question 14

End product inhibition.

Answer 14

-

Question 15

Molecules needed for enzyme function. - Cofactor.

Answer 15

• Inorganic molecule.
• Binds loosely to enzyme.
• Obtained via diet.
• E.g. Cl- (needed for amylase to form correctly shaped enzyme)

Question 16

Molecules needed for enzyme function. - Coenzymes.

Answer 16

• Organic molecule.
• Mostly derived from vitamins.
• E.g. Vitamin B3 (needed to synthesise NAD) - NAD is a coenzyme used in respiration.

Question 17

Molecules needed for enzyme function. - Prosthetic groups.

Answer 17

• Tightly bound- form a permanent part of enzyme.
• E.g. Zn2+ (important part of structure of carbonic anhydrase) - enzyme in metabolism of CO2.

Question 18

Molecules needed for enzyme function. - Precursor activation.

Answer 18

1. Addition of cofactor.
   
   • Before, enzyme= apoenzyme. After, enzyme= haloenzyme.
2. Change in conditions.
   
   • Example= Pepsinogen. Released into stomach. Acidic pH causes conversion to pepsin.
     WHY NEEDED?
3. To activate enzyme in certain conditions.
4. To prevent enzyme damaging tissues.