Practice important
Alpha-Amylase Induction
MCQ questions and answers.
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MCQ Questions
1. In a germinating cereal grain, gibberellin released from the embryo most directly induces alpha-amylase production in which tissue?
A.
The aleurone layer surrounding the endosperm
B.
The vascular cambium of the embryo
C.
The seed coat epidermis
D.
The root cap of the emerging radicle
Correct Answer:
The aleurone layer surrounding the endosperm
Explanation:
Gibberellin produced by the embryo diffuses to the aleurone layer, where it induces synthesis and secretion of alpha-amylase. The enzyme hydrolyses endosperm starch to soluble sugars that nourish the growing embryo.
2. What is the immediate nutritional significance of gibberellin-induced alpha-amylase in a germinating cereal seed?
A.
It converts stored starch into soluble sugars usable by the embryo
B.
It converts amino acids directly into cellulose for the growing root
C.
It converts stored lipids into starch within the endosperm
D.
It prevents hydrolysis of endosperm reserves until photosynthesis begins
Correct Answer:
It converts stored starch into soluble sugars usable by the embryo
Explanation:
Alpha-amylase hydrolyses starch in the endosperm, generating soluble carbohydrates such as maltose and dextrins. These products support respiration and growth of the developing embryo.
3. Which experimental result most strongly demonstrates that gibberellin induces alpha-amylase synthesis rather than merely activating pre-existing enzyme?
A.
A rise in alpha-amylase activity occurs only after transcription and translation are permitted
B.
Alpha-amylase activity increases immediately when the seed is exposed to light
C.
Starch disappears from the endosperm even when aleurone tissue is removed
D.
The embryo grows despite complete inhibition of protein synthesis
Correct Answer:
A rise in alpha-amylase activity occurs only after transcription and translation are permitted
Explanation:
If inhibitors of transcription or translation prevent the gibberellin response, the result supports de novo synthesis of alpha-amylase. This distinguishes induction of enzyme production from simple activation of a pre-existing enzyme.
4. A cereal aleurone tissue is treated with gibberellin in the presence of a transcription inhibitor. Which outcome is most likely?
A.
Alpha-amylase induction is greatly reduced because formation of the required mRNA is blocked
B.
Alpha-amylase induction is enhanced because transcription normally represses the enzyme
C.
Starch hydrolysis becomes independent of gibberellin because the inhibitor supplies sugars
D.
The aleurone immediately secretes all alpha-amylase stored before treatment
Correct Answer:
Alpha-amylase induction is greatly reduced because formation of the required mRNA is blocked
Explanation:
Gibberellin promotes gene expression leading to alpha-amylase production. Blocking transcription prevents formation of alpha-amylase mRNA and therefore strongly suppresses new enzyme synthesis.
5. Which sequence best represents the gibberellin-dependent events during mobilization of starch reserves in a cereal grain?
A.
Embryo produces gibberellin → aleurone synthesizes alpha-amylase → starch is hydrolysed → sugars nourish the embryo
B.
Endosperm produces alpha-amylase → embryo destroys gibberellin → starch is synthesized for seedling growth
C.
Aleurone absorbs starch → embryo converts it into gibberellin → alpha-amylase is degraded
D.
Seed coat produces gibberellin → starch enters the embryo intact → alpha-amylase inhibits respiration
Correct Answer:
Embryo produces gibberellin → aleurone synthesizes alpha-amylase → starch is hydrolysed → sugars nourish the embryo
Explanation:
The embryo supplies the gibberellin signal, the aleurone responds by producing and secreting alpha-amylase, and the enzyme releases soluble sugars from endosperm starch for embryonic growth.
6. A mutant cereal embryo produces normal amounts of gibberellin, but its aleurone cells lack functional gibberellin receptors. Which response is expected?
A.
Normal alpha-amylase induction because gibberellin acts directly on starch
B.
Little or no alpha-amylase induction because aleurone cells cannot perceive gibberellin
C.
Excessive alpha-amylase induction because receptor loss mimics continuous signaling
D.
Normal starch breakdown because the seed coat compensates by secreting alpha-amylase
Correct Answer:
Little or no alpha-amylase induction because aleurone cells cannot perceive gibberellin
Explanation:
Gibberellin must be perceived by receptors in responsive aleurone cells. Without functional perception, the signaling pathway leading to alpha-amylase gene expression cannot be effectively activated.
7. Why does removal of the embryo from an otherwise intact cereal grain usually reduce alpha-amylase production in the aleurone?
A.
The principal source of the gibberellin signal is removed
B.
The embryo is the only tissue containing stored starch
C.
The embryo normally prevents alpha-amylase secretion by the aleurone
D.
The embryo converts alpha-amylase into starch before secretion occurs
Correct Answer:
The principal source of the gibberellin signal is removed
Explanation:
The developing embryo provides gibberellin that reaches the aleurone and induces alpha-amylase synthesis. Removing the embryo therefore removes the major hormonal stimulus for this response.
8. In a de-embryonated cereal grain, which treatment would most directly restore alpha-amylase induction in the aleurone?
A.
Applying gibberellin to the aleurone region
B.
Applying cellulose to the seed coat
C.
Applying auxin only to the dry endosperm
D.
Removing additional aleurone cells from the grain
Correct Answer:
Applying gibberellin to the aleurone region
Explanation:
Exogenous gibberellin can substitute for the hormonal signal normally supplied by the embryo. When applied to responsive aleurone tissue, it induces alpha-amylase synthesis and secretion.
9. Which observation would indicate that a treatment affects alpha-amylase secretion from aleurone cells rather than alpha-amylase synthesis?
A.
Alpha-amylase accumulates inside aleurone cells while little enzyme appears in the surrounding endosperm
B.
Alpha-amylase mRNA and enzyme production both disappear after gibberellin treatment
C.
Starch hydrolysis increases only after new alpha-amylase protein is detected
D.
Aleurone cells show increased transcription of the alpha-amylase gene
Correct Answer:
Alpha-amylase accumulates inside aleurone cells while little enzyme appears in the surrounding endosperm
Explanation:
Intracellular accumulation with reduced extracellular enzyme indicates that alpha-amylase is being synthesized but not efficiently secreted. This separates the secretion step from gibberellin-dependent enzyme synthesis.
10. A cereal aleurone preparation is exposed to gibberellin, and alpha-amylase activity rises only when calcium ions are available. What does this result most directly suggest?
A.
Calcium participates in the signaling or activation process associated with the gibberellin response
B.
Calcium replaces gibberellin as the primary hormonal signal
C.
Calcium prevents starch from serving as the substrate for alpha-amylase
D.
Calcium converts alpha-amylase into a storage protein before secretion
Correct Answer:
Calcium participates in the signaling or activation process associated with the gibberellin response
Explanation:
Calcium ions can function as intracellular signaling components in the gibberellin response of aleurone cells. Their requirement indicates involvement in the pathway leading to effective alpha-amylase production or action, not replacement of gibberellin.
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Alpha-Amylase Induction
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