Digestive system

Question 1

What is the digestive system?

Answer 1

A group of organs that work together to break down and absorb food.

Question 2

What happens during the digestive system?

Answer 2

During digestion, large, insoluble molecules are broken down into smaller soluble molecules by enzymes. The small molecules can then be absorbed into the bloodstream and used by the body’s cells.

Question 3

Name the different parts of the digestive system

Answer 3

Mouth
Salivary glands
Oesophagus
Liver
Gall bladder
Stomach
Pancreas
Large intestine
Small intestine
Rectum
Anus

Question 4

Label the digestive system

file:///C:/Users/44748/Documents/GCSE%20Biology/digestive%20system%20not%20labelled.pdf

Answer 4

https://bam.files.bbci.co.uk/bam/live/content/zgbvw6f/large

Question 5

State the function of mouth

Answer 5

The mouth physically breaks down food into smaller pieces

Question 6

State the function of the salivary glands

Answer 6

The salivary glands produce saliva that contains enzymes

Question 7

State the function of the Gullet (Oesophagus)

Answer 7

Oesophagus is the tube the food travels down to the stomach

Question 8

What does the stomach do?

Answer 8

The stomach churns food with enzymes and acid

Question 9

What does the liver do?

Answer 9

The liver releases bile into the stomach to break down fats

Question 10

What does the Pancreas do?

Answer 10

The Pancreas produces digestive juices containing enzymes

Question 11

What does the small intestine do

Answer 11

In the small intestine, small molecules pass through the wall of the small intestine into the blood stream

Question 12

What does the Large intestine do

Answer 12

In the large intestine, water gets reabsorbed

Question 13

What does the rectum do

Answer 13

The rectum stores the faeces until it leaves the body

Question 14

What does the Anus do

Answer 14

The Anus is a muscular ring through which food passes from the body

Question 15

How is the small intestine adapted for absorbing the products of digestion

Answer 15

The wall of the small intestine is covered in tiny structures called villi.
These villi stick out of the wall and increase the surface area so large amounts of nutrients can pass through.

Microvilli (found on the surface of villi) increase the surface area even further.

The wall of the small intestine has a thin membrane.
The thin membrane ensures a short diffusion path.

The villi have a very good blood supply. The blood capillaries rapidly remove the products of digestion. This increases the concentration gradient.

The small intestine is very long (the human small intestine has a length of around 5m). This provides a very large surface area for absorption of the products of digestion.

All these features mean that there is a rapid rate of diffusion.

Any molecules which cannot be absorbed by diffusion are absorbed by active transport.

Question 16

Why does the stomach produce hydrochloric acid

Answer 16

The stomach produces hydrochloric acid,
to kill bacteria
To give the right pH for the protease enzyme (pespin) to work (which is pH 2 - acidic)

Question 17

Where is the bile made and stored

Answer 17

The bile is made in the liver and it is stored in the gall bladder

Question 18

Why is bile alkaline

Answer 18

The HCl in the stomach makes the pH too acidic for enzymes in the small intestine to work properly.
The Bile is alkaline to neutralises the acid and makes conditions in the small intestine alkaline.
The enzymes in the small intestine work best in these conditions

Question 19

How does the bile help with the digestion of fats

Answer 19

Bile is alkaline to neutralise the hydrochloric acid from the stomach.

The bile emulsifies fats to form small droplets. This increases the surface area of fat for the lipase enzyme to work on.
The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.

Question 20

Describe the process of digestion

Answer 20

1) The mouth physically breaks down food into smaller pieces. Enzymes (Amylase) in the saliva begin to digest the starch into smaller sugar molecules

2) The food travels down the oesophagus into the stomach

3) In the stomach, the food is churned with enzymes and acids. Protease enzymes (pepsin) begin the digestion of proteins in the stomach. The churning action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest, this makes the digestion of proteins faster.

4) The food passes into the small intestine. At this point chemicals are released into the small intestine from the liver and the pancreas.

The pancreas releases protease and amylase enzymes which continue the digestion of starch and protein. The pancreas also releases lipase, to start the digestion of lipids.

The liver releases bile which helps to speed up the digestion of lipids by the process of emulsification - breaking the fat into tiny droplets. The bile also neutralises the hydrochloric acid released from the stomach and makes conditions alkaline.
The enzymes in the small intestine work best in these alkaline conditions.

The walls of the small intestine release protease, amylase and lipase to continue the complete digestion of protein, lipids and carbohydrates.

5) In the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or active transport.

6) The digested food travels through the large intestine, where water is excess water is absorbed into the blood stream.

7) The faeces (undigested food), stored in the rectum, is released from the body by the anus.

Question 21

What are the products of digestion used for by the body

Answer 21

The products of digestion are used by the body, to build new carbohydrates, lipids and proteins. Some of the glucose produced is used in respiration

Question 22

Why are large food molecules digested into smaller soluble ones

Answer 22

Large food, insoluble molecules are too big to pass through the walls of the digestive system, so they have to be broken down into smaller soluble molecules.

Question 23

Name the enzymes that break down proteins

Answer 23

Proteins are broken down by enzymes called proteases

Question 24

Name the enzymes that break down carbohydrates (specifically starch)

Answer 24

Starch (a type of carbohydrate) is broken down by enzymes called amylase.

Question 25

Name the enzymes that break down lipids

Answer 25

Lipid molecules are broken down by enzymes called lipase

Question 26

Where in the digestive system is protease produced

Answer 26

Proteases are produced by the stomach, pancreas and small intestine

Question 27

Where in the digestive system is amylase produced

Answer 27

Amylase is produced by the salivary glands, the pancreas and the small intestine

Question 28

Where in the digestive system is lipase produced

Answer 28

Lipase molecules are produced in the pancreas and the small intestine.

Question 29

What do the protease enzymes convert the protein into.

Answer 29

The protease enzymes convert the protein back to individual amino acids, which are absorbed into the bloodstream

Question 30

What do the amylase enzymes convert the carbohydrate/starch into.

Answer 30

The amylase enzymes convert the starch into simple sugars

Question 31

What do the lipase enzymes convert the lipids into.

Answer 31

The lipase enzymes convert the lipids into fatty acids and glycerol