Nutrition (Digestion)

Question 1

What are the structures that food passes through in the human alimentary canal in order?

Answer 1

• Mouth
• Oesophagus
• Stomach
• Small Intestine (Duodenum and Ileum)
• Large intestine (Colon and Rectum)
• Anus

The liver, gall bladder, pancreas and bile duct are also essential for digestion, but food does not pass through them

Question 2

What are the functions of the mouth/salivary glands?

Answer 2

• Mechanical digestion where teeth break down food, increasing its surface area
• Amylase in saliva begin to break down the starch

Question 3

What are the functions of the oesophagus?

Answer 3

• Connects the mouth to the stomach
• Food is moved down it by wave-like contractions without relying on gravity

Question 4

What are the functions of the stomach?

Answer 4

• Mechanically digests food by churning it
• Protease enzymes like pepsin begin to work
• The hydrochloric acid kills off bacteria and provides the optimum pH for pepsin

Question 5

What are the functions of the small intestine?

Answer 5

• Food is digested by pancreatic enzymes in the duodenum
• Food and water is abosrbed in the ileum

Question 6

What are the functions of the large intestine?

Answer 6

• Water is absorbed from undigested material to produce faeces in the first part called the colon
• The faeces are stored for conveinant release in the rectum to be moved out of the anus

Question 7

What are the functions of the pancreas?

Answer 7

• Releases amylase, protease and lipase
• Secretes them into the duodenum

Question 8

What is the purpose of peristalsis?

Answer 8

To move food along the alimentary canal without the help of gravity

Question 9

Where does peristalsis happen?

Answer 9

• The oesophagus
• The stomach
• The small intestine
• The large intestine

In the stomach and small intestine, peristalsis is also used for the mechanical breakdown of the bolus into a less solid form called chyme

Question 10

How does peristalsis work?

Answer 10

• Circular and longitudinal muscles work in an antagonistic muscle pair
• They contract rhythmically in a wave-like action to move the food along

Mucus continuously lubricates the food, and dietary fibre is required for the muscles to push against

Question 11

What are the roles of digestive enzymes?

Answer 11

To speed up and lower the activation energy of the chemical reactions involved in the chemical breakdown of food

Question 12

What are the three enzymes produced in the pancreas? (Pancreatic enzymes)

Answer 12

• Lipase
• Protease
• Amylase

Question 13

What does amylase break down into what and where is it produced?

Amylase is a carbohydrase enzyme

Answer 13

• It breaks down starch into maltose
• It is produced in the salivary glands, pancreas, and also the small intestine

Question 14

What does maltase break down into what and where is it produced?

Answer 14

• It breaks down maltose into glucose
• It is produced in the small intestine

Question 15

What do all proteases break down into what?

Answer 15

Proteins into amino acids

Question 16

What is the protease enzyme produced in the stomach called and what does it break down into what?

Answer 16

• Pepsin
• It breaks down proteins into amino acids

Pepsins optimum pH is 2, which is why it is in the stomach

Question 17

What do the protease enzymes produced in the pancreas and small intestine break down?

Answer 17

Proteins into amino acids

Question 18

What does lipase break down into what and where is it produced?

Answer 18

• It breaks down lipids into glycerol and fatty acids
• It is produced in the pancreas only

Question 19

Where is bile produced?

Answer 19

The liver

Question 20

Where is bile stored before release to the small intestine through the bile duct?

Answer 20

The gall bladder

Question 21

What are the functions of bile?

Note that the bile salts are what are doing these things

Answer 21

• Neutralises stomach acid allowing optimum pH for pancreatic enzymes once in the duodenum
• Mechanical breakdown of lipids into smaller droplets to increase surface area for lipase (emulsification)

Question 22

How is the small intestine adapted for absorption?

The small intestine absorbs food through diffusion or active transport

Answer 22

• It has an extremely high surface area because it is very long and has millions of villi
• Peristalsis occurs here, which mixes up food and enzymes and keeps food moving, allowing for easier absorbtion and mechanically digesting it
• The production of enzymes turns the food molecules into smaller molecules which are easier to absorb

Question 23

How is the villus adapted for absorption?

Answer 23

• Many microvilli for increased surface area
• Very thin wall for short diffusion distance
• A network of blood capillaries which take amino acids and glucose away to the blood maintain a steep concentration gradient
• A lacteal that runs thorugh the middle takes fatty acids and glycerol away, which also helps to main a steep concentration gradient
• Enzymes assisting in chemical digestion are produced in the walls of the villus

All of these factors are very favourable for diffusion