1. What is the importance of maintaining a stable core temperature and stable blood pH in humans ?
Answer
To ensure enzyme activity continues.
2. Describe the ways in which insulin controls blood glucose concentration.
Answer
Insulin controls blood glucose concentration by binding to receptors on the surface of target cells. This binding triggers the incorporation of channel proteins into the cell-surface membrane, which increases the cell's permeability to glucose and allows more glucose to enter. In addition, insulin activates enzymes that convert glucose into glycogen, thereby reducing the concentration of glucose in the blood.
3. What is the role of the hypothalamus in osmoregulation ?
Answer
The hypothalamus contains osmoreceptors that are sensitive to changes in the water potential of the blood. When the water potential becomes too low, the hypothalamus sends impulses to the posterior pituitary gland, which then releases ADH. This hormone increases the permeability of the distal convoluted tubule and the collecting duct, allowing more water to move by osmosis out of the tubules and back into the blood.
4. The figure below shows the changes in blood glucose concentration and the changes in the two hormones involved in controlling blood glucose. Name hormones X and Y.
Answer
X = glucagon because it rises just before glucose concentration rises and falls when glucose concentration rises
Y = insulin because as glucose concentration rises so does insulin concentration
5. The figure below shows the second messenger model involved in availability of glucose in muscle cells. Identify structures 1–5.
Answer
1 = adrenaline,
6. Molecule 1 is only able to bind to cells with a G protein-coupled receptor. Explain why.
Answer
Adrenaline is only complementary to this receptor due to the receptor's specific tertiary structure.
7. Explain how stimulating the release of ADH increases blood pressure.
Answer
ADH causes more water to be reabsorbed from the filtrate into the blood. This increases blood volume.
8. The figure below shows the concentration of some substances present in the filtrate of a healthy person in different parts of the kidney, expressed as a proportion of the original mass filtered into the Bowman's capsule. Explain the changes in sodium ion concentration between X and Y.
Answer
Water is removed from the filtrate by osmosis, increasing the sodium ion concentration.
9. Explain the changes in sodium ion concentration between Y and Z.
Answer
Between Y and Z sodium ions are actively transported out of the ascending limb.
10. Describe the line on the graph that would represent the expected shape of the "water" line when ADH is not secreted.
Answer
Line drawn above the water line following similar pattern. Line must only be higher in distal convoluted tubule and collecting duct.