Nutrient Digestion and Absorption

Question 1

what does lactose break down into?

Answer 1

glucose and galactose

Question 2

what does sucrose break down into?

Answer 2

glucose and fructose

Question 3

what does maltose break down into?

Answer 3

2 glucose monomers

Question 4

what bonds link monomers in starch and glycogen?

Answer 4

alpha-1,4 glycosidic bonds

Question 5

what enzyme breaks down polysaccharides into disaccharides?

Answer 5

amylase

Question 6

how does glucose enter cells in the brush border of the gut?

Answer 6

through sodium coupled transporter SGLT1

Question 7

how does glucose leave the cell in the gut and enter the blood?

Answer 7

glucose accumulates in the cell, increasing the concentration to above 5mm at which point it leaves the cell down the conc. gradient through a facilitated transporter GLUT 2.

Question 8

what sugar enters the blood the same way as glucose?

Answer 8

galactose

Question 9

how does fructose enter the blood stream?

Answer 9

it enters the cell through GLUT-5 then leaves via GLUT-2 by facilitated transport.

Question 10

how do amino acids enter the blood stream?

Answer 10

they enter the cell through a sodium coupled amino acid transporter. they then leave the cell through a specific amino acid transporter.

Question 11

describe how peptides are taken into the bloodstream

Answer 11

the acid microclimate at the brush border means peptides are transported into the cell at a hydrogen ion coupled transporter. the peptides the enter the blood through facilitated transport while the h ion returns to the lumen via a sodium coupled hydrogen transporter

Question 12

what enzyme breaks down triacylglycerol?

Answer 12

lipase

Question 13

what is triacylglycerol broken down into?

Answer 13

monoglyceride and 2 fatty acids

Question 14

define emulsification

Answer 14

dividing larger droplets into smaller droplets

Question 15

name emulsifying agents

Answer 15

> bile salts

> phospholipids

Question 16

what two things emulsify fats in the stomach?

Answer 16

> mechanical disruption

> emulsifying agents

Question 17

how do the emulsifying agents prevent the small droplets of fat from reforming?

Answer 17

they are amphipathic, non-polar facing inwards and polar facing outwards. the polar charge repels other droplets (as they have the same charge) preventing them from reforming.

Question 18

what makes up a micelle?

Answer 18

> bile salts
monoglyceride
fatty acid
phospholipid

Question 19

what size are micelles?

Answer 19

> 4-7 um

Question 20

describe the process of fats in micelles getting in the epithelial cells

Answer 20

the micelle breaks down at the membrane due to the acid microclimate which makes it uncharged so unstable. this releases small amounts of fatty acids and monoglyceride into solution which diffuses across the membrane into absorbing cells.

Question 21

what happens to the fatty acids/monoglycerides when they enter the cell?

Answer 21

they enter the smooth endoplasmic reticulum where they are reformed into triacylglycerol by enzymes.

Question 22

what is triacylglycerol coated with in the smooth endoplasmic reticulum inside the cell?

Answer 22

an amphipathic protein (emulsification)

Question 23

what happens to the triacylglycerol after it has been emulsified in the cell?

Answer 23

it is transported through vesicles, processed in the Golgi apparatus and exocytosed to extracellular fluid

Question 24

what are chylomicrons?

Answer 24

extra cellular fat droplets containing phospholipids, cholesterol and fat soluble vitamins

Question 25

what do chylomicrons pass into between endothelial cells?

Answer 25

lacteals

Question 26

what two classes of vitamins?

Answer 26

> fat soluble vitamins

> water soluble vitamins

Question 27

how do fat soluble vitamins enter the cell?

Answer 27

follow the same absorption pathway as fat

Question 28

how do water soluble vitamins enter the cell?

Answer 28

through carrier mediated diffusion

Question 29

what problems occur in vitamin b12 deficiency?

Answer 29

pernicious anaemia: blood cells fail to mature, symptoms have a slow onset due to large stores in the liver.

Question 30

how are iron ion transported into duodenal enterocytes?

Answer 30

via DMTI

Question 31

what is ferritin?

Answer 31

a protein iron complex that binds iron in the cell to stop the production of harmful free radicals

Question 32

what happens to unbound iron?

Answer 32

it is transported across the serosal membrane and binds to transferrin in the blood

Question 33

what happens to ferritin?

Answer 33

it is shed with the intestinal cells and passed out in faeces

Question 34

what does ferritin expression depend on?

Answer 34

the body’s iron status

Question 35

does hyper anaemia have increased or decreased ferritin levels?

Answer 35

increased, more iron is bound in enterocytes