Bio Chapter 4 - Enzymes

Question 1

What are enzymes?

Answer 1

A substance that can speed up a chemical reaction without itself being chemically changed at the end of a reaction

Question 2

What are enzymes made up of?

Answer 2

Proteins that function as biological catalysts

Question 3

What are the two properties of enzymes?

Answer 3

Soluble in water
Able to diffuse through cell membranes

Question 4

Name the four digestive enzymes

Answer 4

Amylase
Maltase
Protease
Lipase

Question 5

What are anabolic reactions

Answer 5

Reactions that build up complex substances

Question 6

Name and explain an example of an anabolic reaction - amino acids

Answer 6

Amino acids are taken into cells to build up proteins
Cyoplasm contains special enzymes to catalyse such reactions

Question 7

Give an example of an anabolic reaction - photosynthesis

Answer 7

Glucose synthesised from carbon dioxide and water
The chemical reactions involved are controlled by enzymes

Question 8

What are catabolic reactions?

Answer 8

Reactions that break down complex substances

Question 9

Give an example of a catabolic reaction - cell respiration

Answer 9

During cell respiration, glucose is broken down to release energy to form carbon dioxide and water

Question 10

Why are enzymes highly specific in action?

Answer 10

Only substances with a complementary shape can bind to the active site and undergo a chemical reaction

Question 11

Explain the lock and key hypothesis

Answer 11

The shape of the substrate and the active site of the enzyme are complementary to each other. When substrate encounters he enzyme which acts like a key, is able to fit into the active site of the enzyme. This forms an enzyme-substrate complex.

Question 12

What happens after the enzyme has broken down the substrate?

Answer 12

The enzyme catalyzes the breakdown of the substrate into its constituents. As the shape of the constituent is different from the initial substance, it no longer fits into the active site and detaches from the enzyme

Question 13

Why are enzymes only required in minute amounts and remain unchanged at the end of the reaction?

Answer 13

The same enzyme molecules can be used over and over again and hence a small amount of enzyme can catalyse the reaction for a large amount of substrate.

Question 14

What are the three factors that affect the rate of enzyme reaction?

Answer 14

Temperature, pH and enzyme-substrate concentration

Question 15

With reference to the graph of the rate of enzyme reaction over temperature of the enzyme environment, what happens at the first stage? - low temperature

Answer 15

An enzyme is less active at low temperatures. KE of the molecules is low. Enzyme and substrate molecules move slowly
The rate of the substrate molecules colliding with the enzyme is low.

Question 16

With reference to the graph of the rate of enzyme reaction over temperature of the enzyme environment, what happens at the second stage? - increasing temperature

Answer 16

As the temperature increases, the rate of enzyme reaction also increases
There is an increase in temperature leading to an increase in KE of the molecules
The rate of effective collision increases
Increase in rate of enzyme-substrate complex formation

Question 17

What is the optimum temperature for most human enzymes

Answer 17

40-45 deg cel

Question 18

With reference to the graph of the rate of enzyme reaction over temperature of the enzyme environment, what happens at the fourth stage? - temperature above optimum temperature

Answer 18

An increase in temperature above the optimum causes a rapid increase in the rate of enzyme reaction
The active site of the enzyme molecule loses its original shape
The shape is no longer complementary to the shape of a substrate molecule

Question 19

With reference to the graph of the rate of enzyme reaction over temperature of the enzyme environment, what happens at the last stage? - denaturation

Answer 19

Denaturation occurs which results in a loss or alteration of the enzyme’s active site. Hence, the substrate can no longer fit into the enzyme’s active site no reaction will occur, and the enzyme is no longer a catalyst.

Question 20

What is denaturation

Answer 20

Denaturation occurs when there is a change in 3d structure of an enzyme or any other soluble protein cuaes by heat or chemicals such as acids and alkalis

Question 21

What happens when enzymes are placed in pH conditions that may vary from the optimum

Answer 21

Denaturation