Chapter 4 - Digestion

Question 1

Give a description of what an enzyme is and does.

Answer 1

All enzymes are proteins that function as biological catalysts. (speed up the rate of a reaction e.g Photosynthesis)

Question 2

What is the molecule on which an enzyme acts ?

Answer 2

substrate

Question 3

What is the molecule formed when the enzyme and substrate react ?

Answer 3

product

Question 4

Explain referencing shape how enzymes work.

Answer 4

The shape of the substrate matches exactly the shape of the enzymes active site. (complementary in shape)

Question 5

Is the enzyme used up in the reaction ?

Answer 5

No, its not changed or used up by the reaction, so it is available to repeat the reaction.

Question 6

What is the model used to show the action of enzymes ?

Answer 6

Lock and key model

Question 7

What principle does the Lock and key model show?

Answer 7

The principle of enzyme specificity.

Question 8

What is enzyme specificity ?

Answer 8

Each enzyme is specific that it will only work on it’s normal substrate. e.g only starch will fit into the active site of amylase.

Question 9

Name the enzyme and product for the substrate carbohydrate

Answer 9

Enzyme: carbohydrase
Product: simple sugar, glucose

Question 10

Name the enzyme and product for the substrate starch

Answer 10

Enzyme: amylase
Product: simple sugar, glucose

Question 11

Name the enzyme and product for the substrate protein

Answer 11

Enzyme: Protease
Product: amino acid

Question 12

Name the enzyme and product for the substrate fat

Answer 12

Enzyme: lipase
Product: glycerol and fatty acids

Question 13

Explain the term inhibitors

Answer 13

They are molecules that fit loosely or partially into the active site of some enzymes.

Question 14

Why do inhibitors slow the rate of a reaction ?

Answer 14

substrate molecules cannot enter and be broken down, which leads to a reduced rate of reaction.

Question 15

What two factors affect the activity of all enzymes ?

Answer 15

Temperature

pH

Question 16

Explain how temperature affects enzyme activity .

Answer 16

At low temps the enzyme and substrate molecules have decreased kinetic energy and move more slowly. this results in few collisions which reduces the rate of the reaction.

Increasing the temp increases the kinetic energy and the number of collisions will increase.

Question 17

Explain the term denaturation.

Answer 17

Increasing temp or pH above the optimum cause a decrease in the activity of the enzyme. This is due to an irreversible change to the shape of the enzymes active site, known as denaturation.

Question 18

Explain how enzyme concentration affects the activity of the enzymes .

Answer 18

The more enzymes there are the faster the enzyme reaction. This is because there are more active sites for the substrates to attach to. (This applies up to a limit because there aren’t enough substrates to react)

Question 19

Give two examples of commercial uses of enzymes.

Answer 19

Biological washing powder and baby foods

Question 20

Why do some enzymes have to be thermostable ?

Answer 20

They may be needed to work at a wide range of temperatures.

Question 21

Give the definition of digestion.

Answer 21

Digestion is the breakdown of large, complex, insoluble molecules into small, simple, soluble ones.

Question 22

What is the main function of the ileum ?

Answer 22

The absorption of the digested food products.

Question 23

How is the ileum adapted for its function ?

Answer 23

Great length (3 meters)
large surface area
good blood supply
thin permeable membranes

Question 24

What are the microscopic outgrowths on the ileum called ?

Answer 24

Villi

Question 25

How are villi adapted to absorption ?

Answer 25

excellent blood supply - the digested food products are quickly transported and replaced with blood low in digested food products. This keeps the concetration gradient high.

The thin permeable surface - they have a single layer of surface epithelium cells. Reduces the distance between the lumen of the gut and the capillaries./

Large SA - their finger like shape increases the SA.