Topic 3. Enzymes

Question 1

most enzyme shape

Answer 1

globular

Question 2

enzymes end in the suffix?

Answer 2

‘ase’

Question 3

applications in biotechnology (4)

Answer 3

• added in animal feed to improve digestion
• clarifying wine
• theraputic drugs
• enzyme inhibitor drugs or poisons

Question 4

fermentation is caused by

Answer 4

yeast secretion not necessarily living yeast cells.

Question 5

The variety of reactions that enzymes catalyse can be divided into just six (6) main classes

Answer 5

1. Oxidoreductases
2. Transferase
3. Hydrolases
4. Lyases
5. Isomerase
6. Ligases

Question 6

these enzymes catalyse oxidation/reduction reactions and this might involve addition/removal of hydrogen atoms, and hence these enzymes are also called dehydrogenases, oxidases, oxygenases, peroxidases, etc. (e.g. lactate dehydrogenase)

Answer 6

Oxidoreductases

Question 7

These enzymes catalyse transfer of functional groups between donor and acceptor molecules (e.g. alanine aminotransferase and aspartate aminotransferase).

Answer 7

transferase

Question 8

These enzymes catalyse reactions that involve addition of water (e.g. phenylalanine hydroxylase).

Answer 8

Hydrolases

Question 9

These enzymes catalyse reactions that involve creation of bonds and can be done by adding water, carbon dioxide, ammonia, etc. (e.g. pyruvate decarboxylase).

Answer 9

Lyases

Question 10

These enzymes catalyses isomerisation (shifts from one isomer to another) e.g. L and D isomers. Mutases shift chemical groups in isomerisation. (e.g. mutarotase).

Answer 10

Isomerase

Question 11

Catalyses reactions in which two chemical groups are joined. They are also called synthetases. (e.g. glutamine synthetase).

Answer 11

Ligases

Question 12

Amylases

Answer 12

Breaks down starch into maltose and glucose which can then be fermented by yeast, used in the brewing industry / beer production. Cleaves a1-4 bond.

Question 13

Pectinases

Answer 13

Breaks down pectin, an insoluble carbohydrate found in fruits, thus they can be used to clarify fruit juice and wine.

Question 14

Invertase

Answer 14

Converts (hydrolyses) the sugar sucrose into x1 glucose and x1 fructose molecule. used in the production of confectionary

Question 15

Proteases

Answer 15

Breaks down proteins, used to tenderise meat, used in meat processing

Question 16

Lipases

Answer 16

Breaks down lipids (fats and oils), used for foam stabilisation in a variety of food production processes.

Question 17

Site on an enzyme where the substrate binds to?

Answer 17

Active site

Question 18

Because enzymes increase the rate of a chemical reaction, the rate of an enzyme-catalysed reaction is normally referred to as its

Answer 18

Enzyme activity

Question 19

Specific Activity of an enzyme.

Answer 19

expresses enzyme activity with respect to total protein.

Question 20

Examples of enzymes used in agriculture biotechnology (4)

Answer 20

Chymosin - making cheese

Phosphotases - phosphorus cycle in the soil and plant growth. They hydrolyse phosphates and make phosphorus in the soil available to plants.

Pectin lyase enzyme - breaks down pectin, preventing hazy wine.

Polygalaturonase - tomato carbohydrate breakdown enzyme (naturally occurring)

Question 21

Xylanase and it’s use in agriculture

Answer 21

Used in poultry (egg) production by ways of adding this enzyme to the feed, increasing the guts ability to digest nutrients in the feed. Increases availability of starch, protein, P and Ca. Chicken and pigs Don’t have a rumen, unable to digest cellulose etc.

Question 22

Enzyme which Releases phosphorus in animal feed production from phytate?

Answer 22

Phytases

Question 23

Phytase, how it works;

Answer 23

60-80% of the mineral P in plant feed for poultry is locked up as phytate. Phytase is an enzyme which breaks down the phytate into a usable P form. Not needed for animals with rumens as bacteria in the rumen emit enough Phytase which efficiently breaks down phytate naturally. This saves P fert prices.

Question 24

Chymosin how it works

Answer 24

Casein contains phenylalanine and methionine amino acids joined together by peptide bonds. Chymosin specifically digests the peptide bonds between the two amino acids. This results in para-caesein chains which are hydrophilic and form a clot with ca2+ ions in the milk.

Question 25

Michael is constant (Km)

Answer 25

Km is defined as [S] which yields 1/2 the maximum velocity of a reaction. You can determine this constant by running experiments for a different set of [S] and plot the Product formed per unit of time.