Digestion

Question 1

What do carbohydrates, lipids and proteins break down into?

Answer 1

Carbohydrate: glucose
Lipids: fatty acids & glycerol
Proteins: amino acids

Question 2

Describe the 4 processes involved in digestion and absorption

Answer 2

1) Ingestion: food taken into mouth
2) Digestion: enzymes break large insoluble molecules into smaller soluble molecules
3) Absorption: products of digestion absorbed into bloodstream
4) Egestion: removal of faeces containing undigested food, bacteria and enzymes

Question 3

What are the two types of digestion that take place in the mouth?

Answer 3

Mechanical; via chewing

Chemical; amylase released from salivary glands turns starch into maltose

Question 4

What is the process that takes place in the oesophagus, stomach and intestines to help move the food down?

Answer 4

Peristalsis; waves of muscular contractions

Question 5

What are the functions of the liver and gall bladder?

Answer 5

Liver: produces bile

Gall bladder: stores and secretes bile

Question 6

What is the function of bile?

Answer 6

1) Neutralises stomach acid in the duodenum prior to the small intestine so that it doesn’t dissolve intestine tissue.
2) Emulsifies fats into smaller droplets (sometimes micelles), this provides a higher surface area for lipase.

Question 7

What is digested in the stomach and how?

Answer 7

Proteins are digested into amino acids by the enzyme pepsin as well as mechanical digestion- peristalsis in the stomach (churning)

Question 8

What cells can be found in the gastric pits of the stomach lining?

Answer 8

1) Mucus cells
2) Chief cells
3) Parietal cells

Question 9

What is the function of mucus cells?

Answer 9

Line the stomach to prevent pepsin enzyme from digesting the stomach

Question 10

What is the function of chief cells?

Answer 10

They produce pepsinogen, which can be activated by pepsin or HCl to convert into pepsin.

Question 11

What does the pancreas do?

Answer 11

Secretes pancreatic juice that contains protease, lipase and amylase.

Question 12

What occurs in the small intestine?

Answer 12

• Digestion and Absorption

Question 13

What chemicals are present in the small intestine?

Answer 13

Bile, amylase, lipase and some gastric juice may enter.

Question 14

What features of the small intestine benefit it’s function?

Answer 14

Villi and microvilli that have good blood supply and can increase surface area for absorption to take place

Question 15

What are the three types of peptidase and what does each one do?

Answer 15

1) exopeptidase- removes terminal amino acids
2) endopeptidase- breaks polypeptides into smaller chains
3) dipeptidase- hydrolyses dipeptides into amino acids

Question 16

What occurs in the large intestine?

Answer 16

This is where water is absorbed

Question 17

How are glucose and amino acids absorbed?

Answer 17

1) Co-transport of Na+ and glucose through the membrane of an epithelial cell
2) Active transport of K+ ions and Na+ ions wiv the use of ATP to maintain a concentration gradient (a potassium pump is used to produce potassium ions)
3) Facilitated diffusion of glucose into capillaries

Question 18

Describe how the small intestine is adapted to its function

Answer 18

1) Large SA- villi/microvilli
2) thin epithelium- short diffusion pathway
3) network of capillaries- good blood supply
4) Mitochondria provide ATP for active transport
5) Lacteals for absorption of digested fats

Question 19

Describe and explain roles of diffusion, facilitated diffusion and active transport in the ileum.

Answer 19

-Diffusion
Down concentration gradient. E.g- micelles moving into epithelial cells and chylomicrons moving into lacteals
-Facilitated diffusion
Down concentration gradient, with help of carrier protein. E.g: amino acids moving into epithelial cells
-Active Transport
Against conc. gradient, requiring ATP,

Question 20

How are lipids absorbed in the digestive system?

Answer 20

1) Bile salts emulsifies fat globules into smaller droplets in the small intestine- this provides a larger surface area
2) Pancreatic lipase digests the far droplets into monoglycerides and fatty acids. These are contained in smaller droplets called micelles
3) Micelles diffuse into the epithelial cells in the small intestine
4) Monoglycerides and fatty acids join together through condensation and form a chylomicron
5) Diffuses into lacteal via exocytosis

Question 21

What makes up a ‘chylomicron’?

Answer 21

Phospholipids, cholesterol, proteins and triglycerides.

Question 22

What is exocytosis?

Answer 22

The process by which a small piece of membrane wraps around the lipid droplet and pinches it off