Chapter 9: Nutrition and the Human Digestive System

Question 1

Where is the bile stored?

Answer 1

The gallbladder.

Question 2

Where does the digestive process begin?

Answer 2

The mouth.

Question 3

What are the cells that line the surface of the stomach and what do they form?

Answer 3

The epithelial cells. They have undergone adaptations in structure and function to form gastric glands.

Question 4

What is the content of saliva and what is its use?

Answer 4

Saliva contains salivary amylase which hydrolyses starch to maltose.

Question 5

What is meant by digestion?

Answer 5

The process that breaks down large and complex pieces of food into smaller and simple pieces that can be dissolved for easy absorption.

Question 6

What does the liver produce?

Answer 6

The bile.

Question 7

What is meant by peristalsis and what is its action on bolus?

Answer 7

Peristalsis is the rhythmic contraction and relaxation of muscles along the alimentary canal. It acts in pushing the bolus through the oesophagus until it reaches the stomach.

Question 8

Name the epithelial cells that line the stomach and the substance they secrete respectively.

Answer 8

Chief cells (secrete pepsinogen), parietal cells (secrete hydrochloric acid) and mucous cells (secrete mucus).

Question 9

Name two other substances received by the duodenum and name their respective origins.

Answer 9

The bile - produced by the liver.
The pancreatic juice - secreted by the pancreas.

Question 10

What are the functions of HCl in the digestion of protein in the stomach?

Answer 10

1. Prepare a medium with a suitable pH (pH1.5 - 20) for pepsin to act.
2. Stop the enzymatic action of salivary amylase.
3. Kill bacteria in food.

Question 11

Name the process of hydrolysis occurring with protein.

Answer 11

Erepsin hydrolyses peptides into amino acids.

Question 12

The presence of food in the mouth stimulates the secretion of saliva from the…

Answer 12

…salivary glands.

Question 13

Where does the bile flow into?

Answer 13

The bile flows into the duodenum through the bile duct.

Question 14

What is the pH range of saliva and how does it affect salivary amylase?

Answer 14

The pH range of saliva is between 6.5-7.5 which is the optimal for the action of salivary amylase.

Question 15

What is the first part of the small intestine to receive chyme?

Answer 15

The duodenum.

Question 16

What does the pancreas secrete and how are they secreted?

Answer 16

The pancreas secretes pancreatic amylase, trypsin and lipase into the duodenum through the pancreatic duct.

Question 17

What is meant by physical digestion and chemical digestion?

Answer 17

Physical digestion: Mechanical breakdown of food to form small particles.
Chemical digestion: Decomposition process of complex molecules into simple molecules.

Question 18

What is pepsinogen and what is its usage?

Answer 18

Pepsinogen is an inactive enzyme that is activated by HCl to become pepsin. Pepsin then hydrolyses proteins into polypeptides.

Question 19

How are both physical and chemical digestions achieved?

Answer 19

Physical digestion: Chewing and peristalsis.
Chemical digestion: Enzyme reaction.

Question 20

How does the ileum affect the optimal action of enzymes?

Answer 20

The alkali medium in the ileum allows enzymes to act at its optimum.

Question 21

The food in the stomach is mixed with gastric juice and is churned by peristaltic action of the stomach wall muscles. The contents in the stomach finally change to a semifluid called…

Answer 21

…chyme.

Question 22

Name the process of hydrolysis occurring with lipids.

Answer 22

Lipase hydrolyses lipids into fatty acids and glycerols.

Question 23

What is the function of mucus in the stomach lining?

Answer 23

To protect the stomach walls from the reaction of HCl and digestive enzymes.

Question 24

What do the glands on the ileum wall secrete?

Answer 24

Mucus and intestinal juice which contains maltase, sucrase, lactase, lipase and erepsin.

Question 25

What are the hydrolytic activities that occur within the duodenum?

Answer 25

1. Pancreatic amylase hydrolyses starch to maltose.
2. Trypsin hydrolyses polypeptides into shorter peptides.
3. Lipase hydrolyses lipids into fatty acids and glycerols.

Question 26

Digestion is made up of two parts, that is, …

Answer 26

… physical digestion and chemical digestion.

Question 27

The small intestine consists of…

Answer 27

…duodenum, jejunum and ileum.

Question 28

Name the processes of hydrolysis occurring with carbohydrates.

Answer 28

1. Maltase hydrolyses maltose into glucose.
2. Sucrase hydrolyses sucrose into glucose and fructose.
3. Lactase hydrolyses lactose into glucose and galactose.

Question 29

What are the functions of the bile?

Answer 29

1. Neutralises the acidic chyme.
2. Prepares an alkali medium (pH 7.6-8.6) for enzyme action in the duodenum.
3. Emulsifies lipids by breaking down lipids into tiny droplets to increase surface area for lipase activity.

Question 30

Why is the ileum adapted to absorb nutrients?

Answer 30

1. The long ileum is adapted to absorb nutrients because its internal layer is folded and covered by tiny projections called villi.

Question 31

What are the adaptations of the villus to absorb nutrients?

Answer 31

1. The epithelial layer of the villus is one cell thick to accelerate nutrient absorption.
2. Goblet cells secrete mucus to aid digestion.
3. The network of blood capillaries helps to transport digestive products to the whole body.
4. Lacteal carries droplets of fatty acids and glycerol.
5. The intestinal glands secrete intestinal juices that have digestive enzymes.

Question 32

What are the tiny projections on the surface of the villus epithelium called?

Answer 32

Microvillus.

Question 33

What is the main adaptation of the microvillus?

Answer 33

Microvillus provides a large surface area to increase the rate of nutrient absorption.

Question 34

How is these digested foods absorbed in the ileum?:
(a) Fructose
(b) Galactose
(c) Amino acids
(d) Vitamins B and C
(e) Water

Answer 34

(a) Facilitated diffusion
(b) Active transport
(c) Active transport
(d) Absorbed with water
(e) Osmosis