Cell Membrane & Transport
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Science is not just about memorizing facts; it is about understanding the "why" and "how" behind natural phenomena. Focus on conceptual clarity rather than rote learning. When practicing MCQs, pay special attention to units of measurement, chemical formulas, and scientific terminologies. Reviewing the explanations for wrong answers is the fastest way to improve your score.
All Questions for: Cell Membrane & Transport
Question 1: The cell membrane is primarily composed of:
- A Phospholipid bilayer
- B Protein monolayer
- C Cellulose strands
- D Chitin
Explanation: The membrane is a phospholipid bilayer with embedded proteins.
Question 2: The heads of phospholipids are:
- A Hydrophilic
- B Hydrophobic
- C Neutral
- D Charged positive
Explanation: Phospholipid heads are hydrophilic (water-loving) and face outward; tails are hydrophobic.
Question 3: The tails of phospholipids are:
- A Hydrophobic
- B Hydrophilic
- C Charged
- D Neutral
Explanation: Phospholipid tails are hydrophobic and face inward, away from water.
Question 4: Simple diffusion is a process that:
- A Moves molecules from high to low concentration without energy
- B Requires ATP
- C Moves molecules against concentration gradient
- D Requires transport proteins
Explanation: Simple diffusion is passive movement of molecules from high to low concentration without energy.
Question 5: Osmosis is the movement of:
- A Water across a semipermeable membrane
- B Solutes across a membrane
- C Ions using ATP
- D Proteins across a membrane
Explanation: Osmosis is the diffusion of water across a semipermeable membrane.
Question 6: Facilitated diffusion differs from simple diffusion because it:
- A Uses membrane proteins but requires no energy
- B Requires ATP
- C Is always active
- D Moves only water
Explanation: Facilitated diffusion uses membrane proteins but is still passive (no ATP required).
Question 7: Active transport differs from passive transport because it:
- A Requires energy to move against gradient
- B Requires no energy
- C Only uses diffusion
- D Only works for water
Explanation: Active transport requires energy (ATP) to move molecules against their concentration gradient.
Question 8: The sodium-potassium pump moves:
- A 3 Na+ out and 2 K+ in
- B 3 K+ out and 2 Na+ in
- C Equal Na+ and K+
- D Only Na+ into the cell
Explanation: The Na+/K+ pump moves 3 Na+ out and 2 K+ into the cell using ATP.
Question 9: The sodium-potassium pump uses how many ATP per cycle?
- A 1 ATP
- B 2 ATP
- C 3 ATP
- D None
Explanation: The Na+/K+ ATPase uses 1 ATP per cycle (moving 3 Na+ out and 2 K+ in).
Question 10: Endocytosis is the process by which cells:
- A Engulf material into the cell
- B Release material out of the cell
- C Divide into two cells
- D Produce ATP
Explanation: Endocytosis takes material into the cell by engulfing it in a vesicle.
Question 11: Phagocytosis is a type of endocytosis that involves:
- A Engulfing large particles
- B Engulfing fluids
- C Releasing waste
- D Producing ATP
Explanation: Phagocytosis is 'cell eating' — engulfing large particles like bacteria.
Question 12: Pinocytosis is a type of endocytosis that involves:
- A Engulfing fluids
- B Engulfing large particles
- C Releasing waste
- D Producing ATP
Explanation: Pinocytosis is 'cell drinking' — engulfing fluids and dissolved substances.
Question 13: Exocytosis is the process by which cells:
- A Release material out of the cell
- B Take material into the cell
- C Divide into two cells
- D Digest bacteria
Explanation: Exocytosis releases materials out of the cell via vesicles.
Question 14: Cholesterol in the cell membrane functions to:
- A Regulate membrane fluidity
- B Increase permeability to all substances
- C Produce ATP
- D Synthesize proteins
Explanation: Cholesterol modulates membrane fluidity — decreasing it at high temperatures and increasing it at low temperatures.
Question 15: A hypertonic solution causes a cell to:
- A Shrink (crenate)
- B Swell (lyse)
- C Remain unchanged
- D Divide
Explanation: In a hypertonic solution, water leaves the cell, causing it to shrink (crenate).
Question 16: A hypotonic solution causes a cell to:
- A Swell (lyse)
- B Shrink
- C Remain unchanged
- D Divide
Explanation: In a hypotonic solution, water enters the cell, causing it to swell and possibly lyse.
Question 17: An isotonic solution causes a cell to:
- A Remain unchanged
- B Shrink
- C Swell
- D Divide
Explanation: In an isotonic solution, there is no net water movement, so the cell remains unchanged.
Question 18: Aquaporins are channel proteins that:
- A Transport water
- B Transport sodium
- C Transport proteins
- D Produce ATP
Explanation: Aquaporins allow rapid water transport across cell membranes.
Question 19: Carrier proteins differ from channel proteins because carrier proteins:
- A Undergo conformational changes during transport
- B Are always passive
- C Only transport water
- D Never use ATP
Explanation: Carrier proteins undergo conformational changes to transport solutes; channels simply open a pore.
Question 20: Receptor-mediated endocytosis is:
- A Selective uptake via membrane receptors
- B Non-selective fluid uptake
- C Bulk engulfment of particles
- D Release of materials
Explanation: Receptor-mediated endocytosis uses membrane receptors to target specific molecules (e.g., LDL uptake).
Question 21: The glycocalyx is:
- A The carbohydrate-rich coat on the cell surface
- B A layer of phospholipids
- C A protein pump
- D A lipid transport protein
Explanation: The glycocalyx is the carbohydrate-rich outer coating of the plasma membrane, involved in recognition and adhesion.
Question 22: Integral membrane proteins are:
- A Embedded within the phospholipid bilayer
- B Attached only to the membrane surface
- C Found only in the nucleus
- D Found only in plant cells
Explanation: Integral proteins are embedded within the phospholipid bilayer — some span the entire membrane.
Question 23: Peripheral membrane proteins are:
- A Attached to the membrane surface
- B Embedded in the bilayer
- C Found in the nucleus
- D Part of the cytoskeleton
Explanation: Peripheral proteins attach to the outer or inner surface of the membrane without embedding in the bilayer.
Question 24: Which is a function of membrane proteins?
- A Act as receptors and channels
- B Produce DNA
- C Synthesize ATP only
- D Store water
Explanation: Membrane proteins act as receptors, channels, enzymes, and structural anchors.
Question 25: Glycoproteins on the cell membrane are involved in:
- A Cell-cell recognition and immunity
- B Photosynthesis
- C ATP synthesis
- D DNA replication
Explanation: Glycoproteins mediate cell-cell recognition, adhesion, and immune responses.