4.1 Enzyme Action

Question 1

What are enzymes?

Answer 1

Globular proteins that act as biological catalysts

Question 2

What is the metabolism?

Answer 2

All of the reactions in a cell

Question 3

What is the metabolism broken down into?

Answer 3

Catabolism and anabolism

Question 4

What is the catabolism?

Answer 4

The reactions that break down molecules (Large –> small)

Question 5

What is the anabolism?

Answer 5

The reactions that build up molecules (Small –> large)

Question 6

What do enzymes do?

Answer 6

They lower the activation energy needed for a reaction to begin

Question 7

What is an extracellular enzyme?

Answer 7

Enzymes that have their effect outside the cells that produce them (eg amylase)

Question 8

What is a substrate?

Answer 8

A substance used or acted on by a process or a substance (eg glucose is a substrate)

Question 9

What is an intercellular enzyme?

Answer 9

Enzymes that have their effect inside the cells that produce them (eg catalase)

Question 10

What factors have an effect on the rate of a chemical reaction?

Answer 10

pH, temperature and pressure

Question 11

What has to occur for a reaction to happen?

Answer 11

Molecules need to collide in the right orientation

Question 12

What is the specificity of an enzyme?

Answer 12

The amount of biological reactions that it will catalyse (typically one)

Question 13

How do enzymes reduce the activation energy?

Answer 13

They help the molecules to collide successfully.

Question 14

What are the names of the two hypotheses which suggest how enzymes work?

Answer 14

Lock and Key theory, and induced fit theory

Question 15

Explain the Lock and Key Theory.

Answer 15

-An area within the tertiary structure of an enzyme has a shape that is complementary to the shape of the specific substrate molecule (ACTIVE SITE)
-Only a specific substrate will fit into the active site of the enzyme.
-When the substrate is bound to the enzyme, and ENZYME-SUBSTRATE COMPLEX is formed.
-The substrates then react, and the products are formed in an ENZYME-PRODUCT COMPLEX
-The R-groups within the enzyme also interact with the substrate, forming temporary bonds, forcing the reaction along
-The products are released, leaving the enzyme UNCHANGED, and able to take part in other reactions

Question 16

Explain the Induced Fit Hypothesis

Answer 16

-Recent evidence suggests that the active site of the enzyme changes shape slightly as the substrate enters
-Initial interaction between the enzyme and substrate is relatively weak, but weak interactions rapidly induce changes in the enzyme’s tertiary structure that strengthen binding, putting strain on the substrate molecule.
-This can weaken particular bonds in the substrate, therefore lowering the activation energy.

Question 17

What do all reactions happening in cells need to make the products needed?

Answer 17

Raw materials

Question 18

How are raw materials needed in reactions supplied to cells?

Answer 18

-Nutrients present in the diet supply the materials
-Nutrients are often found in the form of polymers, so are broken down by extracellular proteins to enter the cell

Question 19

Describe the steps involved in the digestion of starch

Answer 19

1- Starch polymers are partially broken down into maltose (catalysed by amylase)
2- Maltose digested into glucose (catalysed by maltase)
3- Glucose is small enough to be absorbed into cells lining the digestive system, before being absorbed into the bloodstream.