3.6 Enzymes

Question 1

Define enzyme

Answer 1

A globular protein which acts as a biological catalyst in metabolic reactions.

Question 2

Define active site

Answer 2

The region on an enzyme where it binds to the substrate.

Question 3

Explain enzyme substrate specificity

Answer 3

Enzymes are very specific and will only catalyse one type of reaction, or a small group of similar reactions. Active site and substrate complement each other in terms of both shape and chemical properties (e.g. opposite charges).

Question 4

Outline the lock and key model

Answer 4

Suggests that the enzyme and substrate possess specific, complementary shapes which fit exactly into each other.

Question 5

Define catabolic reactions

Answer 5

Breaking down reactions.

Question 6

Define anabolic reactions

Answer 6

Building up reactions.

Question 7

Define metabolic reactions

Answer 7

Reactions within the body.

Question 8

Explain the effects of temperature on enzyme activity

Answer 8

Low temperatures result in insufficient thermal energy for the activation of a given reaction. Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity.Once above the optimum temperature (peak rate of activity) enzyme begins to denature, resulting in a loss of enzyme activity.

Question 9

Explain the effects of pH on enzyme activity

Answer 9

Enzymes have an optimum pH and moving outside of this range will always result in a diminished rate of reaction. Changing the pH will alter the charge of the enzyme, may change the shape of the molecule, will diminish its ability to bind to the substrate, inhibiting enzyme function.

Question 10

Explain the effect of substrate concentration on enzyme activity

Answer 10

Increasing substrate concentration will increase the activity of a particular enzyme. More substrate means there is an increased likelihood of enzyme and substrate colliding and reacting. Once all enzymes have been saturated, the rate of reaction will cease to rise regardless of further increases to substrate concentration, graph plateaus.

Question 11

Define denaturation

Answer 11

Structural change in a protein that results in the loss (usually permanent) of its biological properties. Heat and pH are two agents which may cause denaturation of an enzyme.

Question 12

Explain the use of lactase in the production of lactose-free milk

Answer 12

Lactase is purified from bacteria (yeast), then bound to an inert substance (alginate beads). Milk is passed over the beads, and lactose in milk is broken down into glucose and galactose by the lactase.

Question 13

Explain the advantages of binding lactase to an inert substance in the production of lactose-free milk

Answer 13

The enzymes can be reused, the product is enzyme free.