3.3.3 digestion and absorption

Question 1

what is the role of the mouth?

Answer 1

mechanical chewing/breakdown

Question 2

what is produced in the liver?

Answer 2

bile

Question 3

where is bile stored?

Answer 3

gall bladder

Question 4

what enzymes and processes occur in the duodenum?

Answer 4

lipids > LIPASE > fatty acid + glycerol
trypsin

Question 5

what enzymes and processes occur in the ileum?

Answer 5

maltose > MALTASE > glucose
sucrose
lactase
(breaking down disaccharides)

Question 6

what is the role of the rectum?

Answer 6

egestion

Question 7

what is the role of the large intestine?

Answer 7

absorbs water and nutrients

Question 8

what enzymes does the pancreas release?

Answer 8

amylase and trypsin

Question 9

what enzymes does the stomach release?

Answer 9

pepsin

Question 10

what is the role of the oesophagus?

Answer 10

peristalsis, wave like contractions

Question 11

what enzymes and processes occur in the salivary gland?

Answer 11

starch > AMYLASE > maltose

Question 12

amylase:

Answer 12

salivary glands (mouth) and pancreas (small intestine) = starch to maltose

Question 13

maltase:

Answer 13

(disaccharide)
epithelial cells in ileum = maltose to glucose

Question 14

sucrase:

Answer 14

(disaccharide)
epithelial cells in ileum = sucrose to glucose and fructose

Question 15

lactase:

Answer 15

(disaccharide)
epithelial cells in ileum = lactose to glucose and fructose

Question 16

what are endopeptidases?

Answer 16

enzymes that hydrolyse internal bonds

Question 17

what are two examples of endopeptidases?

Answer 17

pepsin and trypsin

Question 18

pepsin:

Answer 18

stomach cells in gastric lining (stomach)
// HCl (optimum acidic conditions)
// protein to smaller polypeptides

Question 19

trypsin:

Answer 19

pancreas (small intestine)
// protein to smaller polypeptides

Question 20

what are exopeptidase?

Answer 20

enzymes that hydrolyse external peptide bonds

Question 21

what are dipeptidases?

Answer 21

enzymes that break a dipeptide into two amino acids.

Question 22

what are bile salts?

Answer 22

bile salts are produced in the liver and split fats and oils into small droplets called micelles.

Question 23

what affect do micelles have on surface area?

Answer 23

droplets increase surface area.

Question 24

how are bile salts formed?

Answer 24

by emulsification

Question 25

what do bile salts associate with?

Answer 25

bile salts stay associated with fatty acids and monoglycerides

Question 26

what is the process of the absorption of fats?

Answer 26

1) movement of ileum contents brings micelles into contact with the brush border and micelles break down. 2) monoglycerides and fatty acids diffuse across membrane into cell (simple diffusion). 3) monoglycerides and fatty acids transported to the smooth endoplasmic reticulum, where they are recombined = triglycerides. 4) triglycerides are transported to the Golgi, where the triglycerides associate with cholesterol and lipoproteins forming chylomicrons. 5) chylomicrons transported by vesicle to the cell membrane and released by exocytosis. 6) chylomicrons enter lacteal. 7) lacteal transports the lipids via the lymphatic system into blood vessels.

Question 27

what are the adaptations of the villi in the ileum?

Answer 27

- lots of mitochondria to make ATP. - large surface area to increase diffusion and active transport.

Question 28

what is the process of the absorption of monomers in the ileum?

Answer 28

1) Na+ actively transported out of epithelial cells into blood by Na+/K+ pump, which uses ATP. 2) produces Na+ concentration gradient (high Na+ concentration in ileum to low concentration in epithelial cells). 3) glucose/amino acids co-transported into epithelial cells with Na+. > glucose/amino acids move against their concentration gradient. > Na+ moves down it's concentration gradient. 4) glucose/amino acids move by facilitated diffusion from epithelial cell into blood (using a carrier protein).