1. What is a major effect of auxin on plant cells in young shoots?
A.
It promotes cell elongation
B.
It prevents water absorption
C.
It destroys the cell wall
D.
It stops cell growth permanently
Correct Answer:
It promotes cell elongation
Explanation:
Auxin stimulates the elongation of cells, especially in young shoot regions, by making the cell wall more extensible.
2. According to the acid-growth hypothesis, auxin promotes cell elongation by increasing the activity of which structures?
A.
Proton pumps in the plasma membrane
B.
Ribosomes in the nucleus
C.
Chloroplasts in the cell wall
D.
Chromosomes in the vacuole
Correct Answer:
Proton pumps in the plasma membrane
Explanation:
Auxin activates proton pumps, which transport hydrogen ions into the cell wall region and help promote wall loosening.
3. What happens to the cell wall during auxin-induced cell elongation?
A.
It becomes more extensible
B.
It becomes completely rigid
C.
It is removed from the cell
D.
It changes into a cell membrane
Correct Answer:
It becomes more extensible
Explanation:
Auxin helps loosen the cell wall, allowing the cell to expand and elongate when water enters the cell.
4. Which ions are pumped into the cell wall region during auxin-promoted cell elongation?
A.
Hydrogen ions
B.
Calcium ions only
C.
Chloride ions only
D.
Iron ions only
Correct Answer:
Hydrogen ions
Explanation:
Auxin stimulates proton pumps to move hydrogen ions into the cell wall, lowering its pH and helping wall-loosening proteins act.
5. Which type of plant cells commonly shows elongation in response to auxin?
A.
Cells in young shoots
B.
Dead cells in heartwood
C.
Cells in dry seeds only
D.
Mature cork cells only
Correct Answer:
Cells in young shoots
Explanation:
Auxin commonly promotes elongation in living, growing cells of young shoots.
6. How does water contribute to auxin-induced cell elongation?
A.
Water enters the cell and helps it expand
B.
Water removes the cell wall
C.
Water stops the proton pumps
D.
Water changes the cell into a root hair
Correct Answer:
Water enters the cell and helps it expand
Explanation:
After the cell wall becomes more extensible, water uptake increases cell volume and causes the cell to elongate.
7. Which protein group helps loosen the cell wall during auxin-induced elongation?
A.
Expansins
B.
Hemoglobins
C.
Antibodies
D.
Keratin proteins
Correct Answer:
Expansins
Explanation:
Auxin promotes conditions that activate expansins, which loosen connections in the cell wall and allow elongation.
8. What is the immediate effect of hydrogen ions in the cell wall during auxin action?
A.
They help lower the cell wall pH
B.
They harden the cell wall completely
C.
They remove water from the cell
D.
They stop cell wall expansion
Correct Answer:
They help lower the cell wall pH
Explanation:
Hydrogen ions make the cell wall more acidic, which supports the activity of wall-loosening proteins and promotes cell elongation.
9. If auxin causes a young shoot cell wall to loosen, what is most likely to follow?
A.
The cell can elongate as it takes up water
B.
The cell immediately dies
C.
The cell loses its plasma membrane
D.
The cell becomes unable to absorb water
Correct Answer:
The cell can elongate as it takes up water
Explanation:
A loosened wall permits expansion, and water uptake increases the cell's size, producing elongation.
10. Which sequence best describes auxin-promoted cell elongation?
A.
Auxin action, proton pumping, wall loosening, water uptake, elongation
B.
Auxin action, wall removal, water loss, cell shrinking
C.
Auxin action, chlorophyll destruction, cell death, elongation
D.
Auxin action, DNA removal, wall hardening, elongation
Correct Answer:
Auxin action, proton pumping, wall loosening, water uptake, elongation
Explanation:
Auxin activates proton pumps, wall loosening follows, water enters the cell, and the cell expands and elongates.
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