3.2 & 3.3 Mechanical And Chemical Digestion & digestive roles of the liver and pancreas

Question 1

What do enzymes do for the digestive system?

Answer 1

Chemically change essential nutrients into smaller, soluble units. This is known as chemical digestion.

Question 2

What does the food have to be in order for the enzyme molecules to get at it?

Answer 2

Small enough, so food must also be physically broken down by mechanical digestion.

Question 3

How does mechanical digestion start?

Answer 3

When we chew our food, making it small enough to swallow.

Question 4

What is the most important part of mechanical digestion?

Answer 4

Muscles in the wall of the stomach churn food around, breaking it up into smaller pieces.
When we vomit, chyme is what we see. Pulverised food provides our digestive enzymes with much easier access to the nutrients.

Question 5

What are the different types of large chemical nutrients?

Answer 5

Proteins, carbohydrates and fats- they are too big to pass through the wall of our gut into the blood and then be carried by it.
They must be dismantled into smaller molecules.

Question 6

How do the large chemical nutrients get dismantled into smaller molecules?

Answer 6

Usually involves breaking the chemical bonds that hold them together. Each action is carried out by a particular enzyme that has the precise shape to carry out its function.
This shape can be distorted by high temperatures and extremes of pH.

Question 7

Enzymes in the digestive system- carbohydrate (starch)

Answer 7

Enzyme- salivary amylase
Result of action- starch to maltose
Site of action- buccal cavity

Enzyme- amylase
Result of action- starch to maltose
Site of action- duodenum

Question 8

Enzymes in the digestive system- carbohydrate (maltose)

Answer 8

Enzyme- maltase
Result of action- maltose to glucose
Site of action- duodenum

Question 9

Enzymes in the digestive system- carbohydrate (sucrose)

Answer 9

Enzyme- sucrase
Result of action- sucrose to fructose and glucose
Site of action- duodenum

Question 10

Enzymes in the digestive system- protein

Answer 10

Enzyme- pepsin
Result of action- protein to polypeptides
Site of action- stomach

Question 11

Enzymes in the digestive system- polypeptides

Answer 11

Enzyme- peptidases e.g. trypsin
Result of action- polypeptides to peptides
Site of action- duodenum

Question 12

Enzymes in the digestive system- peptides

Answer 12

Enzyme- peptidases
Result of action- peptides to amino acids
Site of action- duodenum

Question 13

Enzymes in the digestive system- fats

Answer 13

Enzyme- lipases
Result of action- fats to fatty acids and glycerol
Site of action- duodenum

Question 14

Enzymes in the digestive system- DNA/chromosomes

Answer 14

Enzyme- nucleases
Result of action- DNA to nucleotides
Site of action- duodenum

Question 15

Why does the reaction stop when it hits the stomach?

Answer 15

Has a very low pH.

It is acidic.

Question 16

What type of acid does the stomach produce?

Answer 16

Hydrochloride acid- produced from pits in the stomach walls to activate an enzyme called pepsin.

Question 17

What does the chyme have to be when it enters the duodenum?

Answer 17

Neutralised- alkaline salts must be added to make the gut contents slightly alkaline. These salts are supplied by the bile from the liver and the pancreatic juice from the pancreas.

Question 18

Enzymes in the digestive system- carbohydrate (starch)

Answer 18

Enzyme- salivary amylase
Result of action- starch to maltose
Site of action- buccal cavity

Enzyme- amylase
Result of action- starch to maltose
Site of action- duodenum

Question 19

Enzymes in the digestive system- carbohydrate (maltose)

Answer 19

Enzyme- maltase
Result of action- maltose to glucose
Site of action- duodenum

Question 20

Enzymes in the digestive system- carbohydrate (sucrose)

Answer 20

Enzyme- sucrase
Result of action- sucrose to fructose and glucose
Site of action- duodenum

Question 21

Enzymes in the digestive system- protein

Answer 21

Enzyme- pepsin
Result of action- protein to polypeptides
Site of action- stomach

Question 22

Enzymes in the digestive system- polypeptides

Answer 22

Enzyme- peptidases e.g. trypsin
Result of action- polypeptides to peptides
Site of action- duodenum

Question 23

Enzymes in the digestive system- peptides

Answer 23

Enzyme- peptidases
Result of action- peptides to amino acids
Site of action- duodenum

Question 24

Enzymes in the digestive system- fats

Answer 24

Enzyme- lipases
Result of action- fats to fatty acids and glycerol
Site of action- duodenum

Question 25

Enzymes in the digestive system- DNA/chromosomes

Answer 25

Enzyme- nucleases
Result of action- DNA to nucleotides
Site of action- duodenum

Question 26

Why does the reaction stop when it hits the stomach?

Answer 26

Has a very low pH.

It is acidic.

Question 27

What type of acid does the stomach produce?

Answer 27

Hydrochloride acid- produced from pits in the stomach walls to activate an enzyme called pepsin.

Question 28

What does the chyme have to be when it enters the duodenum?

Answer 28

Neutralised- alkaline salts must be added to make the gut contents slightly alkaline. These salts are supplied by the bile from the liver and the pancreatic juice from the pancreas.

Question 29

Why else do the pancreas and walls of the duodenum supply further digestive enzymes?

Answer 29

Bring necessary changes to carbohydrates, proteins, fats as well as to the DNA that makes up the genes and chromosomes found in the cells of the food we eat.

Question 30

What is another problem for chemical digestion in the gut?

Answer 30

The presence of water.
Fats and water don’t mix.
Salts in bile break fats up into tiny globules that firm into an emulsion, allowing the fat-digesting enzymes to reach the fat molecules.

Question 31

What does the gallbladder store?

Answer 31

Bile which it releases when fat is eaten. The more fat eaten in a meal, the more bile is produced.

Question 32

What has happened by the time chyme reaches the ileum of the small intestine?

Answer 32

The bulk of the nutrients are in a form that is readily absorbed.