Explain crenation and lysis in animal cells

2.4.12 · Biology › Cell Membrane & Transport

Animal cell mein koi cell wall nahi hoti. Plant cell ki wall paani rush karne par push back karti hai, isliye plant cells kabhi burst nahi hoti (woh turgid ho jaati hain). Animal cell membrane patli aur floppy hoti hai, isliye:

woh andar dab jaati hai jab paani bahar jaata hai (shape hold karne ke liye koi internal pressure nahi) → crenation
woh khiench ke phat jaati hai jab paani andar aata hai (pressure resist karne ke liye kuch nahi) → lysis

QUANTITATIVELY kaise reason karein

Hum water potential $Ψ$ (units: kPa) se net water flux model kar sakte hain.

Solute potential derive karna (van 't Hoff, gas-law analogy se): $Ψ_{s} = - i M R T$

Yeh step kyun? Dissolved particles ek "gas" ki tarah behave karte hain jo osmotic pressure $Π = i M R T$ exert karta hai. Osmotic pressure paani ko andar kheechtaa hai, jo potential mein negative contribution hai, isliye minus sign.

$i$ = ionisation factor (e.g. NaCl → 2), $M$ = molarity, $R = 8.31 J mol^{- 1} K^{- 1}$ , $T$ in K.

Direction rule (the payoff): $Net water flow direction = from higher Ψ \to lower Ψ$

Agar $Ψ_{o u t s i d e} < Ψ_{ce l l}$ (bahar zyada negative = hypertonic) → paani bahar jaata hai → crenation.
Agar $Ψ_{o u t s i d e} > Ψ_{ce l l}$ (bahar kam negative = hypotonic) → paani andar aata hai → lysis.
Agar barabar → isotonic → koi net movement nahi.

Figure — Explain crenation and lysis in animal cells

Worked examples

Common mistakes (Steel-manned)

Recall Feynman: 12-saal ke bachche ko samjhao

Socho tumhari cell ek chhota water balloon hai. Paani salty side ki taraf sneek karna pasand karta hai.

Ise salty paani mein daalo → paani bahar sneek karta hai → balloon kishmish ki tarah sikarta hai = crenation.
Ise saade paani mein daalo → paani andar sneek karta hai → balloon bhar ke PHAT jaata hai = lysis.
Ise bilkul sahi paani mein daalo → kuch nahi hota. Isliye doctors tumhari veins mein special salty water use karte hain (saada paani nahi) — taaki tumhare blood balloons na phootein!

Active recall — flashcards

Crenation kya hai?

Hypertonic solution mein osmosis se paani bahar jaane par animal cell ka sikarjna/shrink hona.

Lysis (haemolysis) kya hai?

Hypotonic solution mein osmosis se paani andar aane par animal cell ka phoolna aur phat jaana.

Kis solution mein animal cell normal rehti hai?

Isotonic (andar aur bahar barabar solute concentration → koi net water movement nahi).

Animal cells kyun lyse hoti hain lekin plant cells burst nahi hoti?

Plant cells mein rigid cell wall hoti hai jo paani entry resist karne ke liye turgor pressure create karti hai; animal cells mein koi wall nahi.

Net water movement ki direction?

High water potential (dilute) se low water potential (concentrated solute) ki taraf.

Hypertonic external solution mein kya change hota hai?

Crenation (paani cell se bahar jaata hai).

IV drip 0.9% NaCl kyun hoti hai?

Yeh blood ke saath isotonic hai, red blood cells ki crenation ya haemolysis rokti hai.

Water potential equation define karo.

Ψ = Ψ_{s} + Ψ_{p}

; animal cell ke liye

Ψ_{p} \approx 0

Solute potential

Ψ_{s}

ka sign?

Hamesha negative ya zero; zyada solute → zyada negative.

Agar

Ψ_{o u t s i d e} > Ψ_{ce l l}

ho toh kya hoga?

Paani cell mein ghusta hai → phoolna → lysis.

Connections

Osmosis — dono processes ka underlying mechanism.
Water Potential — direction predict karne ka quantitative tool.
Tonicity - Hypertonic Hypotonic Isotonic
Plasmolysis and Turgor in Plant Cells — plant-cell counterparts.
Selectively Permeable Membrane
Red Blood Cell Structure — kyun RBCs classic example hain.
Diffusion vs Osmosis vs Active Transport

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