digestion and absorption

Question 1

lipid absorption and digestion stages
(8)

Answer 1

1. bile slats emulsify lipid droplets into smaller droplets - increases SA for faster hydrolysis by lipase
2. triglycerides hydrolysed into glycerol, fatty acids and monoglycerides
3. bile salts, glycerol and fatty acids form micelles
4. which bring fatty acids to the surface of the epithelial cell membrane and make fatty acids soluble in water
5. fatty acids enter epithelial cell by simple diffusion
6. Smooth ER - fatty acids and glycerol are recombined to form triglycerides
7. Golgi body- triglycerides modified, proteins added, form chylomicrons which are packaged into vesicles
8. chylomicrons are transported into lymph vessel by exocytosis then enter blood

Question 2

digestion definition

Answer 2

large biological molecules hydrolysed into smaller molecules that can be absorbed across cell membrane

Question 3

epithelial cell adaptation

Answer 3

microvilli on cell membrane which increases surface area for disaccharides and dipeptides

Question 4

protein digestion stages
(6)

Answer 4

1. begins in stomach
2. endopeptidase hydrolyse peptide bonds within polypeptide chain
3. produce smaller polypeptide chains which increases the SA for next enzyme, making digestion faster and more efficient
4. exopeptidase removes one amino acid at a time by hydrolysing peptide bonds at terminal ends of polypeptide chain
5. produces amino acids and dipeptides
6. dipeptdase hydrolyses dipeptides into amino acids which can be absorbed my facilitated diffusion, cotransport and active transport

Question 5

where are the enzymes involved in the digestion of starch produced

Answer 5

amylase= salivary glands and pancreas
maltase= within membrane of epithelium cell membrane of ilieum

Question 6

starch digestion stages
(5)

Answer 6

1.food enters mouth, broken up by teeth, mixed with saliva
2. salivary amylase hydrolyses glycosidic bonds in starch into maltose
3. salivary amylase denatures in stomach due to acidic pH
4. pancreatic amylase continues to hydrolyse starch into maltose
5. maltase (membrane-bound) hydrolyses maltose into glucose which is absorbed into blood

Question 7

how is glucose absorbed from the ileum into the blood

Answer 7

1. Na+ actively transported out of epithelial cell into blood by Na/K pump, using ATP for energy
2. creating a conc gradient of Na+
3. Na+ and glucose enter cell by facilitated diffusion using co-transporter proteins
4. Na+ moves into cell down its concentration gradient
5. glucose moves into cell against its concentration gradient
6. glucose moves into blood by facilitated diffusion

Question 8

where is bile produced, stored and released

Answer 8

produced = liver
stored = gall bladder
released = small intestine with food

Question 9

what does bile contain

Answer 9

bile salts
to emulsify fat droplets to form micelles and increase SA for faster hydrolysis by lipase