Cell Membrane

Q1: What is the primary structure of the cell membrane?
A: A phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

Q2: What does “selectively permeable” mean?
A: The membrane allows some substances to pass while blocking others.

Q3: What is the role of cholesterol in the membrane?
A: It stabilizes membrane fluidity and prevents fatty acid chains from packing too tightly.

Q4: What are integral proteins?
A: Proteins embedded within the membrane that often span the entire bilayer.

Q5: What are peripheral proteins?
A: Proteins attached to the membrane surface, not embedded within the bilayer.

Q6: What is the fluid mosaic model?
A: A model describing the membrane as fluid with proteins moving within a flexible lipid bilayer.

Q7: What is passive transport?
A: Movement of substances across the membrane without energy input.

Q8: What is diffusion?
A: The movement of molecules from high to low concentration without energy.

Q9: What is facilitated diffusion?
A: Passive movement of molecules through transport proteins.

Q10: What is osmosis?
A: Diffusion of water across a selectively permeable membrane.

Q11: What is active transport?
A: Movement of substances against their concentration gradient using ATP.

Q12: What is the sodium-potassium pump?
A: An active transport protein that exchanges 3 Na⁺ out of and 2 K⁺ into the cell using ATP.

Q13: What is endocytosis?
A: The process of engulfing material into the cell via vesicles.

Q14: What is exocytosis?
A: The release of substances from the cell via vesicles fusing with the membrane.

Q15: What are glycoproteins and glycolipids?
A: Carbohydrate-attached proteins and lipids used for cell recognition.

Q16: What role do protein channels play in transport?
A: They allow specific molecules to pass through the membrane.

Q17: What types of molecules pass easily through the membrane?
A: Small, nonpolar molecules like O₂ and CO₂.

Q18: What types of molecules require transport proteins?
A: Large, polar, or charged molecules like glucose and ions.

Q19: How does membrane composition affect fluidity?
A: More unsaturated fats and cholesterol increase fluidity.

Q20: Why is membrane fluidity important?
A: It allows for membrane flexibility, self-repair, and proper function of proteins.