Q.88 Some species of beetles and fishes can survive at sub freezing temperature. They accomplish this
by maintaining cellular integrity using one of the following mechanisms.
(A) Expressing anti-freeze proteins
(B) Accumulating fats
(C) Increasing accumulation of complex polyols
(D) Reducing the availability of total water in the body
Beetles and fishes survive sub-freezing temperatures primarily by expressing anti-freeze proteins (AFPs), which bind to ice crystals to prevent cellular damage and maintain integrity.
This mechanism is well-documented in freeze-avoiding and freeze-tolerant species.
Correct Answer
(A) Expressing anti-freeze proteins
Option Analysis
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(A) Expressing anti-freeze proteins: AFPs adsorb to ice crystal surfaces via hydrogen bonding, inhibiting growth and recrystallization. This creates thermal hysteresis, lowering the freezing point without colligative effects, preserving cell membranes in species like winter flounder and certain beetles.
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(B) Accumulating fats: Fats provide insulation and energy but do not directly protect against intracellular ice formation; they lower the freezing point colligatively but insufficiently for sub-zero survival without other mechanisms.
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(C) Increasing accumulation of complex polyols: Polyols (e.g., glycerol) act as cryoprotectants by colligative depression and stabilizing proteins, common in insects, but the question specifies “one of the following” with AFPs as the precise cellular integrity mechanism via ice-binding.
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(D) Reducing the availability of total water in the body: Dehydration (anhydrobiosis) aids some insects but risks desiccation; it does not maintain cellular integrity during extracellular freezing, unlike AFPs which actively control ice.
Mechanisms in Beetles and Fishes
AFPs in fishes like Zoarces americanus bind ice via threonine repeats, stopping pyramidal plane growth. Freeze-tolerant beetles use AFPs with ice-nucleating proteins to form controlled extracellular ice, sparing cells. Polyols complement but AFPs are key for integrity.
Beetles Fishes Sub-Freezing Anti-Freeze Proteins: Survival Mechanism
Species of beetles fishes sub-freezing anti-freeze proteins rely on this for non-stop cellular protection in extreme cold. Anti-freeze proteins (AFPs) bind ice lattices, preventing lethal recrystallization and membrane rupture during winter dormancy.
Key Mechanisms Compared
| Mechanism | How It Works | Suitability for Beetles/Fishes |
|---|---|---|
| Anti-freeze proteins | Ice-binding halts growth; thermal hysteresis | Primary for cellular integrity |
| Fats | Insulation/energy reserve | Secondary; no ice control |
| Complex polyols | Colligative freeze-point depression | Supports but not specific |
| Reduce body water | Limits ice nuclei | Risks dehydration |
Beetles fishes sub-freezing anti-freeze proteins strategy matches GATE Life Sciences focus on adaptations. Insects initiate controlled freezing; fishes avoid it entirely.
Practical Insights for GATE Prep
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AFPs: Type I-IV plus AFGPs; evolved convergently.
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Examples: Beetle Tenebrio molitor, fish Pseudopleuronectes americanus.
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Test tip: Distinguish freeze-tolerance (AFP+INPs) vs. avoidance (AFPs alone).
