biology : class11 Malting Industry Application : Functions, Effects, Applications : Gibberellin MCQ Questions and Answers
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Malting Industry Application
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MCQ Questions
1. In barley malting, the principal immediate biochemical effect of gibberellin released from the embryo is to stimulate the aleurone layer to produce which enzyme most directly responsible for mobilizing endosperm starch?
A.
Alpha-amylase
B.
Cellulase
C.
Nitrogenase
D.
Polyphenol oxidase
Correct Answer:
Alpha-amylase
Explanation:
During malting, embryo-derived gibberellin signals the aleurone cells to synthesize and secrete hydrolytic enzymes, especially alpha-amylase, which breaks down starch in the endosperm into smaller sugars.
2. Which sequence most accurately represents gibberellin-mediated starch mobilization during barley malting?
A.
Embryo releases gibberellin → aleurone produces alpha-amylase → endosperm starch is hydrolyzed
B.
Endosperm releases gibberellin → embryo produces chlorophyll → starch is converted directly into cellulose
C.
Aleurone releases gibberellin → endosperm produces nitrogenase → starch is converted into proteins
Explanation:
The embryo is the source of the germination signal, gibberellin acts on the aleurone layer, and the resulting alpha-amylase secretion mobilizes stored starch in the endosperm during malting.
3. Why is gibberellin useful in the malting industry when a batch of barley shows delayed or uneven germination?
A.
It can promote coordinated enzyme production in the aleurone layer, improving starch mobilization during malting
B.
It permanently converts barley starch into ethanol before fermentation begins
C.
It prevents the embryo from germinating while increasing seed dormancy
D.
It replaces the need for water uptake during the steeping stage
Correct Answer:
It can promote coordinated enzyme production in the aleurone layer, improving starch mobilization during malting
Explanation:
Gibberellin helps synchronize the germination signal and induces aleurone-derived hydrolytic enzymes, making endosperm reserves more uniformly available for subsequent brewing processes.
4. A barley grain used for malting has a viable embryo but an experimentally removed aleurone layer. If gibberellin is added externally, which outcome is most likely?
A.
Starch mobilization will remain severely impaired because the principal enzyme-secreting tissue is absent
B.
Starch will be fully hydrolyzed because gibberellin directly acts as alpha-amylase
C.
The embryo will produce ethanol directly from stored starch
D.
The endosperm will regenerate the aleurone layer in response to gibberellin
Correct Answer:
Starch mobilization will remain severely impaired because the principal enzyme-secreting tissue is absent
Explanation:
Gibberellin is a regulatory hormone, not a digestive enzyme. Its major malting action depends on the aleurone layer responding by synthesizing and secreting hydrolytic enzymes.
5. In a malting experiment, gibberellin treatment increases alpha-amylase activity but does not itself supply a carbon source. What does this indicate about its role?
A.
It acts as a signal that induces enzyme production rather than serving as the substrate for starch breakdown
B.
It functions as the final sugar product of starch hydrolysis
C.
It chemically replaces starch as the main storage reserve
D.
It inhibits aleurone metabolism while directly dissolving starch granules
Correct Answer:
It acts as a signal that induces enzyme production rather than serving as the substrate for starch breakdown
Explanation:
In malting, gibberellin regulates gene expression and enzyme secretion in the aleurone layer. The enzymes, not gibberellin itself, hydrolyze endosperm starch.
6. Which malting-stage intervention most directly uses the physiological action of gibberellin to increase the availability of fermentable carbohydrates for brewing?
A.
Applying gibberellin during controlled barley germination to enhance aleurone hydrolytic-enzyme production
B.
Applying gibberellin after all enzymes have been destroyed by kilning to restore living aleurone cells
C.
Applying gibberellin only after fermentation to convert ethanol back into maltose
D.
Applying gibberellin to dry barley without water so that enzyme secretion occurs in dormant grains
Correct Answer:
Applying gibberellin during controlled barley germination to enhance aleurone hydrolytic-enzyme production
Explanation:
Gibberellin acts during germination, when the embryo–aleurone signaling system is active. Its application at this stage can promote production of enzymes that release fermentable sugars from the endosperm.
7. If gibberellin is applied to malting barley but the grains are prevented from imbibing water, why would the expected increase in alpha-amylase production be limited?
A.
Water uptake and active germination are needed for the embryo–aleurone signaling and enzyme-synthesis processes
B.
Gibberellin is rapidly converted into starch only in hydrated grains
C.
Dry grains contain no endosperm starch for gibberellin to recognize
D.
Water directly destroys gibberellin before it reaches the embryo
Correct Answer:
Water uptake and active germination are needed for the embryo–aleurone signaling and enzyme-synthesis processes
Explanation:
Gibberellin-mediated malting depends on metabolically active, hydrated grains. Without imbibition, germination-related signaling and protein synthesis in the aleurone are greatly restricted.
8. Which observation would provide the strongest evidence that gibberellin has improved the malting quality of a barley sample?
A.
Higher aleurone-derived alpha-amylase activity accompanied by greater production of soluble sugars from endosperm starch
B.
Lower water absorption and complete suppression of embryo growth
C.
Increased accumulation of undegraded starch in the endosperm
D.
Reduced hydrolytic-enzyme activity despite normal germination
Correct Answer:
Higher aleurone-derived alpha-amylase activity accompanied by greater production of soluble sugars from endosperm starch
Explanation:
Effective gibberellin action in malting should enhance aleurone enzyme production and consequently increase the conversion of stored starch into soluble sugars useful in brewing.
9. Why must gibberellin treatment in malting be carefully controlled rather than applied indiscriminately at very high levels?
A.
Excessive or poorly timed stimulation can disturb the balance between germination, reserve mobilization, and preservation of malt quality
B.
High gibberellin concentrations convert all malt enzymes into structural proteins
C.
Gibberellin permanently prevents starch hydrolysis once alpha-amylase is formed
D.
Any gibberellin treatment immediately sterilizes barley and stops all biochemical activity
Correct Answer:
Excessive or poorly timed stimulation can disturb the balance between germination, reserve mobilization, and preservation of malt quality
Explanation:
Malting requires controlled germination and enzyme development. Gibberellin is therefore used in relation to dose and timing so that enzyme production is enhanced without compromising the desired malt characteristics.
10. A barley line has an aleurone layer that cannot respond to gibberellin, although its embryo produces the hormone normally. What malting defect would be expected?
A.
Insufficient alpha-amylase production and poor conversion of endosperm starch into soluble sugars
B.
Excessive starch hydrolysis caused by constitutive enzyme secretion
C.
Normal starch conversion because gibberellin acts directly on starch granules
D.
Enhanced ethanol formation inside ungerminated barley grains
Correct Answer:
Insufficient alpha-amylase production and poor conversion of endosperm starch into soluble sugars
Explanation:
The aleurone must perceive gibberellin to activate hydrolytic-enzyme synthesis. If this response is defective, the signaling pathway fails even though the embryo supplies the hormone.
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