Stomach, Duodenum and Ileum

Question 1

where is the enzyme pepsin created?

Answer 1

the gastric glands in the stomach

Question 2

enzyme pepsin when reacted with protein?

Answer 2

protein —-pepsin—-> peptide

Question 3

how does the contractions of the stomach wall help enzymes?

Answer 3

it causes mixing of the contents of the stomach, maximising contact between enzymes and food

Question 4

what is pepsin’s optimum pH?

Answer 4

around 2 (an acidic pH)

Question 5

how are the conditions in the stomach made acidic?

Answer 5

due to the release of hydrochloric acid by the gastric glands

Question 6

how does the stomach stop hydrochloric acid from burning through the stomach?

Answer 6

it is covered by a mucus lining

Question 7

what is the two main functions of hydrochloric acid?

Answer 7

• to optimise pH levels for pepsin
• to kill bacteria and fungi in the food we eat

Question 8

where do digestion and absorption happen?

Answer 8

in the small intestine (digestion only happens in the duodenum)

Question 9

where is the final site of chemical digestion?

Answer 9

the duodenum

Question 10

what enzymes do the pancreas make?

Answer 10

• trypsin
• amylase
• lipase

Question 11

where does the pancreas secrete its enzymes?

Answer 11

the duodenum

Question 12

enzyme trypsin when reacted with protein?

Answer 12

protein —-trypsin—-> peptide

Question 13

enzyme amylase when reacted with starch?

Answer 13

starch —-amylase—-> maltose

Question 14

enzyme lipase when reacted with lipids?

Answer 14

lipid (fat) —-lipase—-> glycerol + 3 fatty acids

Question 15

which enzymes does the duodenum wall produce and secrete into the duodenum?

Answer 15

• maltase
• peptidase

Question 16

enzyme maltase when reacted with maltose?

Answer 16

maltose —-maltase—-> glucose

Question 17

enzyme peptidase when reacted with peptide?

Answer 17

peptide —-peptidase—-> amino acids

Question 18

where is bile produced?

Answer 18

the liver

Question 19

where is bile stored?

Answer 19

the gall bladder

Question 20

where is bile released into after being stored?

Answer 20

the duodenum (through the bile duct)

Question 21

what are the two functions of bile?

Answer 21

• neutralises stomach acid - enzymes in the duodenum work best at 7-8
• emulsifies lipids - breaks down large droplets into smaller droplets, increasing surface area for lipase to digest the fats

Question 22

where does absorption happen?

Answer 22

in the ileum

Question 23

how are small soluble molecules absorbed into the villi?

Answer 23

• diffusion
• active transport

Question 24

how is the ileum adapted to increase the rate of diffusion?

Answer 24

• large surface area - folding of ileum, villi and microvilli (folds on the surface of cells lining the villi)
• short diffusion distance - the villi walls are one cell thick
• high concentration gradient - provided by capillary network and lacteals removing absorbed molecules