digestion & absorption exam qs

Question 1

co transport steps

Answer 1

1) sodium ions + glucose co transported from lumen to epithelium
2) sodium goes down conc gradient, glucose against
3) sodium ions actively transported from epithelium into blood via carrier proteins
4) potassium ion pumped from the blood into epithelium (ensures conc gradient)
5) glucose is transported from epithelium into the blood via facilitated diffusion through channel proteins

Question 2

receptors

Answer 2

require channel proteins

Question 3

water potential

Answer 3

the tendency for water to move from one place to another
(e.g if there’s lots of water on the left side of the membrane it will move to the right side where there’s less water molecules = down a wp gradient from a high to low water potential)

Question 4

Describe the mechanism for the absorption of amino acids in the ileum

Answer 4

Facilitated diffusion of amino acid
2. Co-transport;
3. Sodium ions actively transported from cell to
blood
4. Creating sodium ion concentration/diffusion
gradient;
5. Facilitated diffusion of amino acid into
blood

Question 5

Use this information and Figure 2 to suggest how eating its own caecal droppings helps a
rabbit’s digestion and absorption of dietary protein.

Answer 5

More/remaining/undigested (protein) broken down;
Accept all (protein) broken down
2.   (So more) amino acids absorbed;
3.   (Because) protein/food passes again through stomach/ileum;

Question 6

What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid
and pepsin?

Answer 6

Mimics / reproduces) effect of stomach.

Question 7

The addition of a respiratory inhibitor stops the absorption of amino acids.
Use the diagram to expain why.

Answer 7

No/less ATP produced
OR
No active transport;
2. Sodium (ions) not moved (into/out of cell);
3. No diffusion gradient for sodium (to move into cell with amino
acid)

Question 8

Describe how you would use a microscope to find the mean diameter of triglyceride
droplets on a slide

Answer 8

Measure with eyepiece graticule / scale;
Calibrate with stage micrometer / scale on slide / object of known size;
Repeats and calculate the mean;