Digestion

Question 1

What are the 7 major parts of the digestive system?

Answer 1

Oesophagus, stomach, ileum, large intestine, small intestine, salivary glands, pancreas, rectum

Question 2

What does the oesophagus do?

Answer 2

Carries food from the mouth to the stomach

Question 3

What is the stomach and what does it do?

Answer 3

Muscular sac with an inner layer and glands that produces enzymes and stores and digests food

Question 4

What is the ileum?

Answer 4

Long muscular tube making up the small intestine that produces enzymes

Question 5

How is the ileum adapted?

Answer 5

Large surface area folded into villi with microvilli to absorb digested food to the bloodstream

Question 6

What is the large intestine?

Answer 6

Absorbs water mainly from the secretion of digestive glands

Question 7

What do the salivary glands do?

Answer 7

Pass secretions via a duct into the mouth contains the enzyme amylase which hydrolyses starch into maltose

Question 8

What is the rectum?

Answer 8

Where faeces are stored before being removed by the anus in a process called egestion

Question 9

What are the 2 stages of digestion?

Answer 9

Physical breakdown and chemical digestion

Question 10

Where does physical breakdown mainly happen? Why does it happen?

Answer 10

In the mouth where large food molecules are broken down into smaller molecules by chewing of the teeth so they have a larger surface area

Question 11

What other place does physical breakdown take place apart from tbe mouth?

Answer 11

Churned up by muscles in the stomach wall

Question 12

What is chemical digestion?

Answer 12

Hydrolysis of large insoluble molecules into smaller more soluble ones by enzymes

Question 13

What enzyme breaks down carbohydrates and what into?

Answer 13

Carbohydrase breaks carbohydrates down into monosaccharides

Question 14

What enzyme hydrolyses lipids and what does it break them down into?

Answer 14

Lipase hydrolyses lipids into glycerol and fatty acids

Question 15

What enzyme hydrolyses proteins and what into?

Answer 15

Protease hydrolysed proteins into amino acids

Question 16

How is starch digested?

Answer 16

1. Amylase in saliva hydrolyse starch into maltose
2. Food enters acidic stomach that denatures amylase preventing hydrolysis
3. In the small intestine it mixes with pancreatic juices containing pancreatic amylase hydrolyses remaining starch into maltose
4. Muscles in intestine wall push good along the ileum and epithelium lining produces maltose a membrane bound disaccharide hydrolysed by maltase into alpha glucose

Question 17

How is ph maintained in saliva?

Answer 17

Mineral salts

Question 18

How is ph maintained in the small intestine?

Answer 18

Alkaline salts

Question 19

How is sucrose digested?

Answer 19

Sucrase hydrolyses single glycosidic bond in the sucrose molecule producing 2 monosaccharides glucose and fructose

Question 20

How is lactose digested?

Answer 20

Lactase hydrolyses single glycosidic bond in lactose producing two monosaccharides glucose and galactose

Question 21

How are lipids digested?

Answer 21

1. Lipase is produced in pancreas which hydrolyses the ester bonds of the triglycerides to form fatty acids and monoglycerides
2. Split up into tiny droplets called micelles by bile salts produced in the liver called emulsification which increases the SA for lipids to act on

Question 22

How are proteins digested?

Answer 22

1. Endopeptidases hydrolyse peptide bonds between amino acids in central region of protein chain forms a series of peptide molecules
2. Exopeptidases hydrolyse peptide bonds of terminal amino acids at end of peptide molecules formed by endopeptidases it releases dipeptides and single amino acids
3. Dipeptidases are membrane bound as found in the lining of the epithelium and they hydrolyse peptide bonds between the amino acids of the dipeptides formed by exopeptidases

Question 23

How are ileum adapted for diffusion?

Answer 23

1. Large surface area villi and microvilli
2. Thin walls short diffusion pathway
3. Muscle and blood vessels carry blood away maintaining diffusion gradients

Question 24

How are amino acids and monosaccharides absorbed?

Answer 24

1. Sodium ions actively transported out of epithelial cells by sodium potassium pump into the blood
2. Higher conc of Na in lumen than epithelial cells
3. Na ions diffuse down conc gradient
4. Amino acids or glucose cotransport into cells with them by facilitated diffusion

Question 25

How are triglycerides absorbed?

Answer 25

1. Triglycerides and fatty acids are emulsifies into micelles by bile salts increasing SA
2. Micelles broken down when they reach lumen of epithelium cells lining into monoglycerides and fatty acids which can diffuse easily into epithelial cells
3. At ER recombined into triglycerides then associate with cholesterol and lipoproteins to form chlyromicrons that can transport them out
4. Move out by exocytosis and enter lacteal found at centre of each villi