Question
▶️Answer/Explanation
The pancreas has both endocrine and exocrine functions.
When blood glucose is low, the alpha cells of the pancreas release glucagon, which stimulates the liver to convert glycogen to glucose.
A (thyroxine) refers to the thyroid gland, not the pancreas.
C is incorrect because insulin is released when blood glucose is high.
D is incorrect because endopeptidases digest proteins, not regulate glucose.
Question
The graph illustrates the relationship between blood glucose levels and liver glycogen concentrations in animals after consuming different glucose meals. Which statement best explains the correlation depicted in the graph?
A. Liver cells store excess blood glucose as glycogen in response to glucagon.
B. Glucagon increases the release of glucose by liver cells to restore concentrations.
C. Insulin decreases respiration rates in liver cells for storage of excess blood glucose.
D. Liver cells respond to insulin by speeding up the conversion of blood glucose into glycogen.
▶️Answer/Explanation
Answer: D. Liver cells respond to insulin by speeding up the conversion of blood glucose into glycogen.
Explanation:
After a meal, blood glucose rises.
The pancreas releases insulin, which signals the liver to store excess glucose as glycogen.
This process lowers blood glucose and increases liver glycogen content.
A is incorrect because glucagon is released when glucose is low, not high.
B refers to glucagon’s opposite function.
C is unrelated; insulin doesn’t directly decrease respiration to store glucose.
Question
Which substances are absorbed by the villi in the small intestine?
A. Glucose, lactose and amino acids
B. Vitamins, polypeptides and fructose
C. Glycerol, fructose and phosphate
D. Fatty acids, maltose and fructose
▶️Answer/Explanation
Answer: C. Glycerol, fructose and phosphate
The villi absorb:
- Monosaccharides like fructose and glucose
- Fatty acids and glycerol from lipid digestion
- Amino acids from protein digestion
Maltose is typically broken down to glucose before absorption, but may be partially absorbed.
A is incorrect because lactose is not absorbed directly; it’s broken into glucose and galactose.
B is wrong as polypeptides are not absorbed, only amino acids.
C includes phosphate, which is absorbed but not as a major product of digestion like the others.
Question
How does auxin exert its effect on plant cells?
A. Acts directly on the cell wall, causing expansion
B. Binds to a receptor resulting in expression of genes
C. Causes the vacuole to absorb water and expand the cell
D. Causes the cell to undergo cell division
▶️Answer/Explanation
Answer: B. Binds to a receptor resulting in expression of genes
Explanation:
Auxin is a plant hormone that binds to specific receptors in plant cells, leading to the activation or repression of certain genes. This gene expression influences various physiological processes, particularly cell elongation.
Here’s how auxin works:
- Auxin enters the cell and binds to a receptor (often part of the TIR1 complex).
- This leads to the degradation of repressors of gene transcription.
- Specific genes are then activated, such as those coding for proton pumps.
- Proton pumps acidify the cell wall, loosening it and allowing the cell to expand in response to internal turgor pressure.
Why the other options are incorrect:
A. It doesn’t act directly on the cell wall but works through gene expression and acid growth theory.
C. Water uptake happens passively in response to osmotic changes but is not the direct effect of auxin.
D. Auxin mainly promotes cell elongation, not cell division (which is more influenced by cytokinins).
Question
How does auxin contribute to phototropism?
A. It increases production of light-sensitive proteins.
B. It increases growth of cells on the shaded side of the stem.
C. It inhibits growth of axillary buds.
D. It inhibits stem elongation.
▶️Answer/Explanation
Answer: B. It increases growth of cells on the shaded side of the stem.
Explanation:
Phototropism is the growth response of a plant toward (or away from) light. In positive phototropism (e.g. in shoots), the plant bends toward the light.
This happens because:
- Auxin, a plant growth hormone, is redistributed to the shaded side of the shoot when light hits one side.
- Auxin stimulates cell elongation on the shaded side.
- As those cells elongate more than those on the light-exposed side, the shoot bends toward the light.
Why the other options are incorrect:
A. Auxin doesn’t directly increase light-sensitive protein production.
C. Inhibiting axillary buds relates to apical dominance, not phototropism.
D. Auxin promotes, not inhibits, stem elongation in shoots.
Question
The diagram shows a plant shoot and the direction of the light which the shoot received.
What are the direction of movement and the effect of auxin in the tip of a plant shoot when receiving light from one side?
▶️Answer/Explanation
Answer: C
Explanation:
When light shines on just one side of a plant shoot, something interesting happens. The plant wants to grow towards the light to get more of it (because light helps it make food through photosynthesis).
To do that, a special plant hormone called auxin moves to the shaded side of the shoot — the side not getting light.
Once auxin is on the darker side, it tells the cells there to grow longer. As those cells grow, they push the plant and make it bend towards the light.
So, in simple words:
- Auxin moves away from the light (to the darker side).
- On that side, it helps the cells grow longer.
- This makes the shoot bend towards the light.