Digestion and Enzymes

Question 1

What is the function of the digestive system?

Answer 1

Your digestive system breaks down the food you eat into smaller soluble molecules so that they can then be absorbed into your bloodstream so your body can use them for energy, growth and repair. Unused materials are discarded as faeces.

Molecules we eat must be broken down becuase they are too large to pass through the wall of the gut

Question 2

Why does your digestive system need to break down the food you eat?

Answer 2

The digestive system needs to break down the food you eat becuase food is made of large insoluble molecules. They can’t pass through the wall of the intestine. Therefore, they need to be broken down to from smaller soluble molecules that can then be absorbed and used by cells.

Question 3

What do enzymes do?

Answer 3

The break down of food is catalysed by enzymes. They increase the rate at which the break down of large insoluble food molecules into smaller soluble ones, occurs

Question 4

Describe the journey food undertakes

Answer 4

mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus

Question 5

What do glands do?

Answer 5

They release digestive juices containing enzymes to break down food molecules

Question 6

What are faeces

Answer 6

Faeces are the material left after water and nutrients have been absorbed into the blood

Question 7

Where is water absorbed into the blood?

Answer 7

large intestine

Question 8

Function of the salivary glands?

Answer 8

These produce the amylase enzyme in saliva

Question 9

Function of the stomach? (2)

Answer 9

1. Pummels food with it’s muscular walls + chemical digestion
2. It produces hydrochloric acid to
   a) kill bacteria
   b) to give the right PH for the protease enzyme to work

Question 10

Function of the gall bladder?

Answer 10

Where bile is stored before being released into the small intestine

Question 11

Function of the liver?

Answer 11

Where bile is produced. Bile neutralises stomach acid and emulsifies lipids.

Question 12

Function of the pancreas?

Answer 12

Produces protease, amylase and lipase enzymes and releases these into the small intestine

Question 13

Function of the small intestine? (2)

Answer 13

1. Produces protease, amylase and lipase enzymes

2. This is where the digested food is absorbed out of the digestive system into the blood.

Question 14

Function of the large intestine?

Answer 14

where excess water is absorbed from the food

Question 15

Function of the rectum?

Answer 15

Where faeces (made up mainly of indigestible foods) are stored before they are excreted through the anus

Question 16

Food test for sugars

Answer 16

Benedict’s solution - Add Benedict’s to the food and boil in a water bath.
Blue → Orange

Question 17

Food test for starch

Answer 17

Iodine - Add a few drops of iodine to the food.

Brown → Black

Question 18

Food test for protein

Answer 18

Biurets solution - add a few drops to food

Blue → Purple

Question 19

Food test for lipids

Answer 19

Ethanol - Add water to food then add water food solution to ethanol
Colourless → cloudy

Question 20

What is a catalyst?

Answer 20

a catalyst is a substance which increases the rate of a reaction, without being changed or used up in the reaction

Question 21

What are enzymes made out of?

Answer 21

Large proteins - and all proteins are made up of a chain of amino acids that are folded into unique shapes

Question 22

What are enzymes?

Answer 22

They are biological catalysts

Question 23

What is the lock and key theory?

Answer 23

Every enzyme has an active site (the region where the substrate binds to the enzyme) that only allows a specific substrate (the substance on which the enzyme acts) to fit, similar to how locks and keys work.

Once the substrate binds to the active site, the reaction takes place rapidly and products are released. The enzyme itself remains unchanged

Question 24

Where is amylase (a carbohydrase) produced? (3)

What does it break starch into?

Answer 24

1. Salivary glands
2. Pancreas
3. Small intestine
   Starch →(amylase)→ sugars

Question 25

Where is protease produced? (3)

What does it break proteins into?

Answer 25

1. Stomach
2. Pancreas
3. Small intestine
   Proteins →(protease)→ amino acids

Question 26

Where is lipase produced? (2)

What does it break lipids into?

Answer 26

1. Pancreas
2. Small intestine
   Lipids →(lipids)→ fatty acids + glycerol

Question 27

What does Bile do to lipids?

Answer 27

bile emulsified fats, which means that bile breaks down fats into tiny little droplets, increasing the surface area of the fat for the enzyme lipase to work on, which makes its digestion faster.

Question 28

What causes a protein to change shape?

Answer 28

Heat

Question 29

Why does heat also speed up chemical reaction?

Answer 29

The molecules get more kinetic energy, which means more frequent collision between particles therefore the rate of the reaction increases

Question 30

Why does heat also speed up chemical reaction?

Answer 30

The molecules get more kinetic energy, which means more frequent collision between particles therefore the rate of the reaction increases

Question 31

What happens when an enzyme is heated past the optimum temperature?

Answer 31

The active site changes shape so the substrate can no longer fit = no more reactions = the enzyme is denatured, this happens at what is known as the peak temperature

Question 32

Describe the graph showing temperature and the rate of enzyme reaction

Answer 32

https://www.evolvingsciences.com/

Temperature%20and%20pH.html

Question 33

Why do plants work slower in the winter?

Answer 33

The rate of reactions of their enzymes are slower becuase of the temperature

Question 34

Why do we sweat or shiver?

Answer 34

To try and keep the body’s heat at/as close to optimum temperature as possible

Question 35

What is another factor apart from temperature, that affects enzymes?

Answer 35

Ph - if the PH is to low or to high it interfears with the bonds holding the enzyme together and changes the shape of the active site, denaturing the enzyme.

Question 36

Pepsin optimum PH

Answer 36

PH 2

Question 37

Describe graph showing PH and rate of enzyme reaction

Answer 37

https://www.pathwayz.org/Tree/Plain/ENZYMES+-pH

Question 38

Calculating rate of reaction

Answer 38

change/time - on a graph draw a tangent

y2-y1) / (x2-x1