Digestion

Question 1

What is the active site on an enzyme?

Answer 1

Part of enzyme molecule substrate molecule fits into as complementary shapes.

Question 2

What is a catalyst?

Answer 2

Something which speeds up rate of reaction but is unchanged by reaction.

Question 3

What does complementary mean?

Answer 3

Shapes that fit into each other.
E.g. enzyme and its substrate.

Question 4

What is denaturation?

Answer 4

Irreversible change in shape of enzyme.
It is no longer complementary to substrate and cannot catalyse reaction.

Question 5

What is digestion?

Answer 5

Enzymes breaking down large, complex, insoluble food molecules into small, simple, soluble ones which can be absorbed across walls of ileum into blood.

Question 6

What is enzyme specificity?

Answer 6

Ability of enzyme to catalyse only one type of substrate.

Question 7

What is an inhibitor?

Answer 7

Molecule which fits into active site of enzyme and stops normal substrate entering so reducing reaction rate of enzyme.

Question 8

What is the ‘Lock and Key Model’?

Answer 8

Model used to explain how enzyme reacts with its substrate.

Question 9

What is a substrate?

Answer 9

Molecule that is acted upon by enzyme.

Question 10

What are villi?

Answer 10

Small finger-like projections lining wall of ileum which increases its surface area for absorption by extending into the lumen.

Question 11

What does optimum mean?

Answer 11

Value of a factor which allows reaction to happen at its fastest rate.

Question 12

What are thermostable enzymes?

Answer 12

Enzymes are to function over wide range of temperatures without being broken down.

Question 13

What are enzymes?

Answer 13

Biological catalysts that speed up rate of reactions without being used up themselves. Made up of proteins.

Question 14

What are the enzyme and products of starch?

Answer 14

Enzyme - amylase
Products - simple sugars, glucose

Question 15

What are the enzyme and products of Fats (lipid)?

Answer 15

Enzyme - lipase
Products - glycerol, fatty acids

Question 16

What is the enzyme and product of protein?

Answer 16

Enzyme - protease
Product - amino acids

Question 17

What are the enzyme and products of carbohydrates?

Answer 17

Enzyme - carbohydrase
Products - simple sugars, glucose

Question 18

What is the ‘Lock and Key Theory’ of enzyme action?

Answer 18

Enzyme’s active site is exact shape of substrate. Enzyme is lock and substrate is key. Two molecules are complementary, ie. they specifically match.

Question 19

How do inhibitors affect the rate of enzyme action?

Answer 19

Molecules called inhibitors fit loosely or partially into active site of enzyme.
While they occupy active site, substrate molecules cannot enter and be broken down, leads to reduced rate of reaction.

Question 20

How does temperature affect enzyme action?

Answer 20

1. Increase in temperature causes kinetic energy of enzyme and substrate molecules to increase.
2. Leads to increases collisions between enzymes and substrates.
3. Leads to more successful collisions.
4. Equals faster rate of reaction.

At optimum temp for enzyme (37-40oC), enzyme works best and has 100% activity.

Question 21

How does denaturation occur?

Answer 21

At high temp molecules have a lot of kinetic energy and vibrate vigorously.
Weakens bonds that hold enzyme in specific shape.
Changes shape of active site and enzyme no longer matches shape of substrate.
Rate of reaction decreases as enzyme can no longer catalyse reaction.

Question 22

How does pH affect enzyme activity?

Answer 22

Each enzyme has optimum pH.
Either side of pH they work less well because shape of active site changes.
At extremes of pH enzyme denatures and stops working.

Question 23

What are examples of different enzymes and their pH conditions?

Answer 23

Amylase (mouth) - slightly alkaline
Trypsin (protease, small intestine) - slightly alkaline
Pepsin (protease, stomach) - acidic

Question 24

How does enzyme concentration affect enzyme activity?

Answer 24

If unlimited supply of substrate, higher enzyme concentration and faster reaction rate.
As enzyme concentration increases more enzyme molecules are in same volume solution and so greater chance of substrate colliding with enzyme active site.
If supply of substrate is limited, rate of reaction levels off as no more substrate molecules to collide with enzyme.

Question 25

What are the uses of enzymes in industry?

Answer 25

Speed up processes and make more efficient.
E.g. production of baby food, cheese making, in biological washing powder, fruit juice production, bread making and alcohol production.

Question 26

Why are thermostable enzymes used in industry and what are their benefits?

Answer 26

Work over wide range of temps.
Break large insoluble stains into small soluble molecules that dissolve in water.
Economic benefits as saves user money for electricity in washing and better for environment.

Question 27

What are the 5 processes in digestion of food?

Answer 27

Ingestion, digestion, absorption, assimilation and egestion.

Question 28

Where do these processes occur?

Answer 28

Ingestion - buccaneers cavity (eating)
Digestion - stomach + duodenum (small intestine)
Absorption - ileum (small intestine)
Assimilation - body cells (building molecules)
Egestion - anus (faeces)

Question 29

What are the adaptations of the ileum (small intestine) for absorption?

Answer 29

Long (3 metres) - more time for absorption of soluble food molecules
Many folds - increases surface area for absorption
Presence of villi (millions) - increases surface area for absorption
Thin membranes - short diffusion distance
Lacteal - absorbs fatty acids and glycerol

Question 30

What are the adaptations of the villi to speed up absorption?

Answer 30

1 cell thick epithelium - allows quick diffusion due to short diffusion distance. Permeable to soluble food molecules.
Rich blood supply - maintained concentration gradient between ileum and capillary network. Promotes diffusion into blood.
Lacteal (lymph vessel) - absorbs fatty acids and glycerol and returns them to blood later.
Microvilli - increase surface area for absorption of food molecules.

Question 31

What is the method for the test for the effect of temperature on enzyme action?

Answer 31

1. Set up 5 water baths at 10oC, 20oC, 30oC, 40oC and 50oC.
2. Label 5 test tubes with ‘starch’ and temp of one of the water baths.
3. Do same with ‘amylase’.
4. Use syringe to measure 5cm3 of 1% starch solution into each test tubes labelled starch.
5. Do same for amylase.
6. Place one starch and amylase labelled test tube in each water bath for at least 5 mins.
7. Prepare spotting tile for each temps by placing one drop of iodine solution in each dimple.
8. Starting with 10oC water bath, pour amylase solution into starch solution. Use clean pipette to sample mixed solution and start timer.
9. Add one drop of sample to iodine solution in first dimple of spotting tile and note any colour change. Return remainder of sample into test tube.
10. Repeat sampling every min and record time taken for starch to be digested.
11. Repeat steps 8, 9 and 10 with each water bath.