PMS · PMS · 2026
Solved PMS 2026 GK practice set on fruit ripening enzymes - ethylene, amylase, pectinase, polygalacturonase and polyphenol oxidase - with verified answers and explanations. A Sir Adnan practice set for PMS Screening preparation, not an official past paper.
Paper Snapshot
Questions
45
Time
45
Minutes
Subjects
1
Topics
1
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About this paper
A Sir Adnan one-liner set headed 'ENZYMES-GK / ONE-LINER-100 (PPSC/FPSC NEW TREND 2026-27)' from the monster-data 'PMS SCREENING 2026 GK UPDATED' pack. Despite its title, the booklet is entirely about fruit ripening: ethylene as the ripening hormone, amylase converting starch to sugar, pectinase and polygalacturonase softening the fruit, lipoxygenase forming aroma, and polyphenol oxidase causing browning. The booklet prints 50 items (4 pp, no options); 45 are published here in the standard MCQ format with verified answers and explanations. Dropped, never inferred: printed Q3 ('direct maturation' is not a standard term for non-climacteric ripening), printed Q34 (pectin degradation does not produce soluble sugars - sweetness comes from starch conversion), and printed Q36, Q37 and Q45 as near-exact internal duplicates of Q10 (tomato softening), Q13 (aroma formation) and Q15 (polygalacturonase acting on pectin). NOTE flags on the polygalacturonase items (it is itself a pectin-degrading enzyme), the banana-yellowing item (chlorophyll breakdown reveals carotenoids), the carbon-dioxide item (the respiratory gas, distinct from the ethylene burst), the non-climacteric item (the booklet's wording, with the on-plant qualification) and the mesocarp item (ethylene is produced by fruit tissues generally).
Paper Controls
Subject 1
Topic Section
45 solved MCQs shown directly below
Correct Answer: Ethylene
Ethylene is the plant hormone that triggers and coordinates fruit ripening.
Correct Answer: Ethylene
Climacteric fruits show a burst of ethylene production that drives their ripening.
Correct Answer: Amylase
Amylase breaks down stored starch into sugars, which is why ripening fruit becomes sweeter.
Correct Answer: Pectinase
Pectinase degrades pectin in the cell walls, so the fruit softens as it ripens.
Correct Answer: Polyphenol oxidase
Polyphenol oxidase (PPO) oxidises phenolic compounds when cut fruit is exposed to air, producing brown pigments.
Correct Answer: Methionine
Plants make ethylene from methionine through the S-adenosylmethionine (SAM) pathway.
Correct Answer: Ethylene
Continued ethylene action past the ripe stage drives over-ripening and decay.
Correct Answer: Pectinase
Pectinase hydrolyses pectin, the cementing polysaccharide of fruit cell walls.
Correct Answer: Polygalacturonase
Polygalacturonase breaks down pectin and is the key softening enzyme in ripening tomatoes.
Correct Answer: Amylase
In ripening bananas, amylase converts stored starch into sugars.
Correct Answer: Polyphenol oxidase
When apple flesh is cut and exposed to air, polyphenol oxidase oxidises phenols and the slices brown.
Correct Answer: Lipoxygenase
Lipoxygenase acts on fatty acids to produce the volatile compounds that give ripening fruit its aroma.
Correct Answer: Ethylene
The climacteric peak is the sharp rise in respiration accompanied by a burst of ethylene production.
Correct Answer: Pectin
Polygalacturonase cleaves the polygalacturonic acid chains of pectin in the cell wall.
Correct Answer: Ethylene
Ethylene is the ripening hormone of climacteric fruits such as banana, mango and tomato.
Correct Answer: Ethylene
Papaya is a climacteric fruit, so its ripening is regulated by ethylene.
Correct Answer: 1-MCP (1-methylcyclopropene)
1-MCP binds ethylene receptors and blocks ethylene action, delaying ripening in stored fruit.
Correct Answer: Sweetness
As starch is converted to sugars, the fruit tastes sweeter.
Correct Answer: Pectin
Softening is mainly the breakdown of pectin in the middle lamella and primary cell wall.
Correct Answer: Chlorophyll degradation
As the banana ripens, green chlorophyll breaks down, revealing the yellow carotenoid pigments underneath.
Correct Answer: Carbon dioxide (CO2)
The climacteric rise in respiration releases extra carbon dioxide as the fruit ripens.
Correct Answer: Amylase
Amylase converts starch to sugars, raising the fruit's sweetness.
Correct Answer: Polygalacturonase
Polygalacturonase degrades pectin in the pulp cell walls, softening the fruit.
Correct Answer: Plant hormone (gas)
Ethylene is a gaseous plant hormone, the only major plant hormone that is a gas at ordinary temperatures.
Correct Answer: Cell wall degradation
Enzymes degrade the cell-wall polysaccharides, so the fruit tissue loses firmness.
Correct Answer: Banana, Mango, Tomato
Banana, mango and tomato are classic climacteric fruits that ripen with an ethylene burst; grape, citrus, cherry, strawberry and pineapple are non-climacteric.
Correct Answer: Grape, Citrus
Grape and citrus are non-climacteric: they do not show an ethylene-driven ripening burst and must ripen on the plant.
Correct Answer: Heat and acid
Heat inactivates polyphenol oxidase (as in blanching) and acid conditions such as lemon juice inhibit it.
Correct Answer: Sugar (glucose/maltose)
Amylase hydrolyses starch into maltose and glucose.
Correct Answer: Pectinase
Pectinase breaks down cell-wall pectin, reducing the fruit's firmness.
Correct Answer: Polyphenol oxidase
Polyphenol oxidase oxidises phenolic compounds in mango flesh, causing browning on cutting or bruising.
Correct Answer: Ethylene
Ethylene triggers the climacteric rise in respiration and ripening.
Correct Answer: Low temperature
Cold storage slows respiration and ethylene action, delaying ripening.
Correct Answer: Amylase
Amylase is the main enzyme of banana ripening, converting its large starch reserves into sugars.
Correct Answer: Pectinase
Pectinase degrades apple cell-wall pectin, so the apple softens as it ripens.
Correct Answer: Phenolic compounds
Enzymatic browning is the oxidation of phenolic compounds to quinones, which polymerise into brown pigments.
Correct Answer: Artificial ripening
Ethylene (or ethylene-releasing compounds) is applied commercially to ripen harvested fruit uniformly.
Correct Answer: Excess softening
Past the ripe stage, continued cell-wall breakdown makes the fruit excessively soft and mushy.
Correct Answer: Slowly without ethylene
Non-climacteric fruits do not show an ethylene burst; they mature gradually on the plant without one.
Correct Answer: Ethylene
Mango is a climacteric fruit whose ripening is triggered by ethylene.
Correct Answer: Respiration rate
The climacteric is defined by a sharp rise in the fruit's respiration rate.
Correct Answer: Mesocarp
In fleshy fruits, ethylene production is concentrated in the mesocarp, the fleshy middle layer of the fruit wall.
Correct Answer: Starch-to-sugar conversion
Ethylene stimulates the ripening programme, including the conversion of stored starch into sugars.
Correct Answer: Pectin hydrolysis
Softening is driven by hydrolysis of pectin in the cell walls.
Correct Answer: Climacteric fruits
Papaya, banana and tomato are all climacteric fruits that ripen with an ethylene burst.
Source & verification
Built by GK360 from verified bank questions — every answer rechecked before publishing. Where the source printed no options, the answer options were prepared by GK360; the questions and correct answers are the verified originals.
Questions
No. It is a Sir Adnan one-liner practice set on fruit ripening enzymes, prepared for PMS Screening 2026. It is published as paperType 'practice', never as a past paper, and the year 2026 is the booklet's label, not a claimed exam session.
Ethylene. It is the gaseous plant hormone that triggers ripening in climacteric fruits such as banana, mango, tomato and papaya, and it can be blocked by 1-MCP.
Amylase. It breaks stored starch down into glucose and maltose, which is why ripening fruit becomes sweeter.
Polygalacturonase is the specific pectin-degrading enzyme the booklet asks for; pectinase is the wider enzyme family it belongs to, so the family name is not offered as a separate option on those items.
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