digestion

Question 1

Describe the process of starch digestion

Answer 1

1. (salivary/pancreatic amylase hydrolyses starch into maltose;
2. By hydrolysing glycosidic bonds;
3. Maltose is hydrolysed into glucose;
4. By Maltase;

Question 2

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.

Answer 2

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 iluem) OR Maintain high(er) concentration of fatty acids/monoglycerides to cell/lining (of the ileum);
3. Fatty acids/monoglycerides absorbed by simple diffusion into epithelial cell;
4. Triglycerides (re)formed (in cells);
5. Vesicles move to cell membrane;

Question 3

Describe the role of micelles in the absorption of fats into the cells of the ileum.

Answer 3

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 4

Describe the role of enzymes in the digestion of proteins in a mammal.

Answer 4

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. Exopeptidases 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 5

Describe the absorption of glucose (Cotransport)

Answer 5

1. Sodium ions actively transported from ileum/epithelial 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;

Question 6

Describe how amino acids are absorbed from the ileum into the blood (5)

Answer 6

1. Sodium ions actively transported out of epithelial cell into the blood (by sodium potassium pump);
2. This creates a concentration gradient for Na+(between lumen of ileum and the epithelial cell);
3. Na+ and amino acid enter by facilitated diffusion;
4. Na+ diffuse into the cell down its concentration gradient;
5. Amino acids move into the cell against their concentration gradient;
6. Amino acids move into the blood by facilitated diffusion;