If human blood is placed in a 2% detergent solution, what will happen to the RBC?
- (a)The RBC will shrink.
- (b)The RBC will swell and become turgid.
- (c)The RBC will swell and burst.
- (d)The RBC will lyse.
Correct — D, the RBC will lyse. A detergent is a surfactant — its molecules have a water-loving head and a fat-loving tail, so they dissolve the lipid bilayer that forms the red blood cell's membrane. Once the membrane is broken apart the cell can no longer hold its contents and ruptures, releasing its haemoglobin; this direct membrane breakdown is called lysis. Because the cause is chemical disruption of the membrane rather than water entering by osmosis, the correct description is simply that the RBC lyses.
- (a)The RBC will shrink. — Shrinking (crenation) happens when a cell loses water to a hypertonic solution; a detergent does not draw water out — it dissolves the membrane.
- (b)The RBC will swell and become turgid. — Turgidity applies to plant cells with a rigid cell wall; an animal RBC has no wall and cannot become turgid, and a detergent does not swell the cell by osmosis in any case.
- (c)The RBC will swell and burst. — This describes osmotic haemolysis in a hypotonic solution, where water enters and the cell swells before bursting. A detergent works differently — it solubilises the membrane directly, so the cell lyses without first swelling.
The red blood cell membrane is a lipid bilayer with embedded proteins. Detergents are amphipathic surfactants that insert into and dissolve this lipid bilayer, destroying the membrane's integrity so the cell breaks open (lysis). This is a chemical disruption of the membrane, distinct from osmotic bursting caused by water entering a cell in a hypotonic solution.
The tempting answer is 'swell and burst' because students recall RBCs bursting in pure water. But that is osmosis; here the agent is a detergent, which lyses the cell by breaking the membrane directly. Detergents are used in laboratories precisely to lyse cells and release their contents.
- Detergents are amphipathic surfactants that dissolve lipid membranes.
- Disrupting the RBC membrane causes lysis — the cell breaks open and releases haemoglobin.
- Osmotic bursting (swell-then-burst) needs a hypotonic solution; detergent lysis is chemical, not osmotic.
- Animal cells lack a cell wall, so they cannot become 'turgid' like plant cells.
- Choosing 'swell and burst' (osmotic) when the agent is a detergent that lyses the membrane chemically.
- Applying 'turgid' to an animal cell, which has no cell wall.
Asked by placing RBCs in different solutions (water, salt, detergent) and predicting whether they shrink, swell or lyse.
Consider the following statements: 1. During the process of osmosis, the solvent travels from the concentrated solution to the dilute solution. 2. In the reverse osmosis, external pressure is applied to the dilute solution. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer(d) Neither 1 nor 2
Same concept — osmosis and how cells behave in solutions of different concentration; understanding water movement across a membrane is the backdrop to distinguishing osmotic bursting from detergent-driven lysis.
Net movement of water from a dilute to a concentrated solution through a selectively permeable membrane is called
- (a) Diffusion
- (b) Dispersion
- (c) Osmosis
- (d) Absorption
Answer(c) Osmosis
Same concept — defines osmosis (water crossing a selectively permeable membrane), the process behind osmotic swelling/bursting that the detergent case is deliberately contrasted with.
Turgid :
- (a) Determined or loyal
- (b) Dirty or untidy
- (c) Swollen or distended
- (d) Excited or upset
Answer(c) Swollen or distended
Related — 'turgid' means swollen/distended, the term used in the wrong option here; turgidity is a walled plant-cell response, not what happens to an RBC in detergent.
- practice — not a real PYQ
Red blood cells placed in distilled water (a hypotonic solution) will
- (a)shrink
- (b)remain unchanged
- (c)swell and may burst
- (d)become turgid
Answer(c) swell and may burst — water enters by osmosis (osmotic haemolysis).
- practice — not a real PYQ
Detergents are able to break open cells because they
- (a)raise the temperature
- (b)dissolve the lipid membrane
- (c)remove all the water
- (d)add salts
Answer(b) dissolve the lipid membrane — as amphipathic surfactants they disrupt the bilayer, causing lysis.