digestion and absorption

Question 1

describe the process involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (5)

Answer 1

1. micelles contain bile salts and fatty acids/monoglycerides;
2. make fatty acids/monoglycerides (more) soluble (in water)
   OR
   bring/release/carry fatty acids/monoglycerides to cell/lining (of the ileum);
   OR
   maintain high(er) concentration of fatty acids/monoglycerides to cell/lining (of the ileum);
3. fatty acids/monoglycerides absorbed by diffusion;
4. triglycerides (re)formed (in cells);
5. vesicles move to cell membrane;

Question 2

explain the function of ATP hydrolase. (2)

Answer 2

1. release energy;
2. (energy) allows ions to be moved against a concentration gradient
   OR
   (energy) allows active transport of ions;

Question 3

the movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.
explain how. (2)

Answer 3

1. (maintains/generates) a concentration/diffusion gradient for Na+ (from ileum into cell);
2. Na+ moving (in) by facilitated diffusion, brings glucose with it
   OR
   Na+ moving (in) by co-transport, brings glucose with it;

Question 4

after collecting samples, the scientists immediately heated them to 70°C for 10 minutes.
explain why. (2)

Answer 4

1. to denature the enzyme/lipase;
2. so no further digestion/hydrolysis occurred;

Question 5

describe the role of micelles in the absorption of fats into the cells lining the ileum. (3)

Answer 5

1. micelles include bile salts and fatty acids;
2. make the fatty acids (more) soluble in water;
3. bring/release/carry fatty acids to cell/lining (of the ileum);
4. maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
5. fatty acids (absorbed by diffusion);

Question 6

describe the role of enzymes in the digestion of proteins in a mammal. (4)

Answer 6

1. (reference to) hydrolysis of peptide bonds;
2. endopeptidase act in the middle of protein/polypeptide
   OR
   endopeptidase produces short(er) polypeptides/increase number of ends;
3. exopeptidase act at end of protein/polypeptide
   OR
   exopeptidase produces dipeptides/amino acids;
4. dipeptidase acts on dipeptide/between two amino acids
   OR
   dipeptidase produces (single) amino acids;

Question 7

the name of the process by which fatty acids and glycerol enter the intestinal epithelial cell. (1)

Answer 7

diffusion;

Question 8

explain the advantages of lipid droplet and micelle formation. (3)

Answer 8

1. droplets increase surface area (for lipase/enzyme action);
2. (so) faster hydrolysis/digestion (of triglycerides/lipids);
3. micelles carry fatty acids and glycerol/monoglycerides to/ through membrane/ to (intestinal epithelial) cell;

Question 9

suggest how golgi apparatus is involved in the absorption of lipids. (3)

Answer 9

1. modifies/processes triglycerides;
2. combines triglycerides with proteins;
3. packaged for release/exocytosis
   OR
   forms vesicles;

Question 10

cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. explain how. (3)

Answer 10

1. sodium ions actively transported from ileum cell to blood;
2. maintains/forms diffusion gradient for sodium to enter cells from gut (and with it, glucose);
3. glucose enters by facilitated diffusion with sodium ions;