digestion & absorption

Question 1

Describe the process of starch digestion

Answer 1

Salivary/pancreaticAmylase;
Maltose;
Maltase;
Maltose to glucose;
Hydrolysis;
Glycosidic bonds;

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 diffusion;
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 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 glucose is absorbed from the ileum into the blood. (5)

Answer 6

1. Na+ is actively transported out of epithelial cell into the blood
2. Creates a concentration gradient of Nat
3. Nat and glucose enter by facilitated diffusion using cotransporter proteins
4. Na+ diffuse into the cell down its concentration gradient
5. Glucose moves into the cell against its concentration gradient
6. Glucose moves into the blood by facilitated diffusion

Question 7

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

Answer 7

1. Nat actively transported out of epithelial cell into the blood
2. Creates concentration gradient of Nat
3. Nat and amino acid enter by facilitated diffusion
4. Na+ moves into cell down its concentration gradient
5. Amino acids move into cell against their concentration gradient
6. Amino acids move into blood by facilitated diffusion

Question 8

Explain the advantage of lipid droplet and micelle formation (3)

Answer 8

1. Lipid droplets increase surface area
2. Faster diffusion / hydrolysis
3. Micelles carry fatty acids to cell membrane of epithelial cell

Question 9

Describe and explain two features you would expect to find in a cell specialised for absorption (2)

Answer 9

1. Folded membrane SO large surface area
2. Large number of co-transport proteins SO fast rate of absorption
3. Large number of mitochondria SO make
   ATP/ for aerobic respiration
4. Membrane bound enzymes SO maintains concentration gradient

Question 10

Describe how the structure of a protein depends on the amino acid it contains (5)

Answer 10

1. Structure is determined by position of amino acid
2. Primary structure is number and sequence of amino acids
3. Secondary structure formed by hydrogen bonding
4. Tertiary structure formed by hydrogen bonds, ionic bonds and disulphide bridges
5. Creates active site in enzymes
6. Quaternary structure contains more than one polypeptide chain