T3

Question 1

Catalyst

Answer 1

A substance which increases the rate of a chemical reaction without itself being changed at the end of the reaction

Question 2

Enzymes

Answer 2

Organic (biological) catalysts which are used to catalyse a vast number of chemical reactions within
living organisms at relatively low temperatures that is between 5 and 40°C

Question 3

Structure of enzyme molecule

Answer 3

1. Enzymes are globular protein
2. Soluble
3. Large molecules (usually much larger than the substrates they act on)

Question 4

Site of enzymes in cells

Answer 4

1. Intracellular

2. Extracellular

Question 5

Intracellular enzymes

Answer 5

Enzymes which are formed and retained in the cell

Question 6

Extracellular enzymes

Answer 6

Enzymes which are produced in the cell and packaged to be secreted from the cell and work externally

Question 7

Mechanism of enzyme action

Answer 7

1. Lock and key hypothesis

2. Induced fit hypothesis

Question 8

Lock and key hypothesis

Answer 8

1. The active site of an enzyme has a specific shape into which the substrate fit exactly
2. Only the substrate molecule whose shape is complementary to the shape of the active site of an enzyme molecule will fit into the active site to form a temporary structure called the enzyme-substrate complex
3. The substrate is analogous to the ‘key’ that fits exactly into the enzyme ‘lock’.
4. Once the product are formed, they no longer fit into the active site & escape into the surrounding medium, leaving the enzyme molecule unchanged and the active site free to bind with further substraet molecules

Question 9

Induced fit hypothesis

Answer 9

1. The active site have more flexible structures
2. The binding of substrate to the active site induces a conformational change in the shape of the active site, which allows the active site to mould itself into a precise shape around the substrate
3. This suggest that the active site of an enzyme has a shape complementary to that of the substrate only after the substrate is bound
4. A suitable analogy would be that of a hand changing the shape of the globe as the glove is put on

Question 10

Properties of enzymes

Answer 10

1. Most enzymes are globular protein
2. They are biological catalyst
3. They are highly specific
4. They are efficient
5. Enzymes lower the activation energy of the reaction they catalyse
6. Rate of enzyme-catalysed reaction is affected by changes in temperature, pH, substrate concentration and enzyme concentration

Question 11

Factors affecting the rate of enzyme-catalysed reaction

Answer 11

1. Effects of varying temperature
2. Effects of varying pH
3. Effects of varying enzyme concentration
4. Effects of varying substrate concentration

Question 12

How enzymes break down substrates

Answer 12

1. Enzymes have active sites (tertiary structure), complementary to substrate
2. Random movement of enzyme and substrate brings them together, binds by active site
3. Enzyme-substrate complex forms temporarily
4. R groups of amino acids in active site interacts with substrate and break it apart
5. Enzyme-product complex forms temporarily
6. Product molecules leave active site, enzyme remains unchanged
7. Enzyme ready to bind with other substrate

Question 13

Enzyme inhibitor

Answer 13

A molecule which prevents an enzyme from catalysing its own reaction. It does so by combining with they enzyme to form an enzyme-inhibitor complex, which thus prevents substrates from entering the enzyme’s active site. The overall effect is to reduce the rate of an enzyme-catalysed reaction.

Question 14

Inhibitors can be divided into two which is

Answer 14

1. Competitive inhibitor

2. Non-competitive inhibitor

Question 15

Shape of competitive inhibitor

Answer 15

Shape that is sufficiently similar to that of the normal substrate.

or

Has a shape that is complementary to that of the active site of an enzyme molecule and thus is able to fit into the active site

Question 16

Characteristic features of a competitive inhibition

Answer 16

1. Inhibition is always reversible

2. At higher substrate concentration, the rate of reaction increases

Question 17

Shape of non-competitive inhibitor

Answer 17

Has a shape that is different to that of the normal substrate

Question 18

Characteristic features of non-competitive inhibition

Answer 18

1. Inhibition is irreversible
2. An increase in substrate concentration does not affect the rate of reaction. The rate of reaction will never attain its Vmax

Question 19

Enzyme cofactors

Answer 19

Cause the enzyme to function more efficiently

Question 20

Cofactors

Answer 20

Enzymes that requires non-protein molecules

Question 21

Three types of cofactors

Answer 21

1. Activators
2. Prosthetic groups
3. Coenzymes