1. What is the primary structure of the plasma membrane?
Answer: A bilayer of phospholipids.
2. What component provides fluidity to the plasma membrane?
Answer: Cholesterol.
3. What is the main role of membrane proteins?
Answer: To assist in transport, signaling, and cell recognition.
4. What is the “fluid mosaic model” of the plasma membrane?
Answer: It describes the plasma membrane as a dynamic structure with proteins floating in or on the lipid bilayer.
5. What does the term “selective permeability” mean in relation to the plasma membrane?
Answer: The ability of the membrane to allow certain substances to pass through while blocking others.
6. What type of molecules can pass easily through the plasma membrane?
Answer: Small nonpolar molecules like oxygen and carbon dioxide.
7. What is the function of glycoproteins in the plasma membrane?
Answer: They aid in cell recognition and communication.
8. What is the difference between passive and active transport?
Answer: Passive transport does not require energy, while active transport requires ATP to move substances against their concentration gradient.
9. What is facilitated diffusion?
Answer: The movement of molecules across the membrane with the help of transport proteins, without energy usage.
10. What type of transport mechanism involves water movement?
Answer: Osmosis.
11. Which transport mechanism moves molecules from a high to low concentration?
Answer: Diffusion and facilitated diffusion.
12. What is the primary function of the sodium-potassium pump?
Answer: To move sodium ions out and potassium ions into the cell, requiring ATP.
13. What is phagocytosis?
Answer: The process of engulfing large particles or microorganisms by the cell.
14. What is pinocytosis?
Answer: The process where the cell engulfs extracellular fluid and its dissolved substances.
15. What is the role of transport proteins in the plasma membrane?
Answer: They facilitate the movement of molecules across the membrane, either by active or passive transport.
16. What happens to a cell in a hypotonic solution?
Answer: The cell swells as water enters the cell.
17. What happens to a cell in a hypertonic solution?
Answer: The cell shrinks as water leaves the cell.
18. What is exocytosis?
Answer: The process by which substances are expelled from the cell in vesicles.
19. What is endocytosis?
Answer: The process by which cells take in substances by engulfing them with the plasma membrane.
20. What role do membrane receptors play?
Answer: They bind to specific molecules, triggering a cellular response.
21. What is the role of the lipid bilayer in the plasma membrane?
Answer: It acts as a barrier to protect the cell and regulates what enters and exits.
22. What is a concentration gradient?
Answer: A difference in the concentration of molecules across a membrane.
23. What is the effect of an isotonic solution on a cell?
Answer: The cell maintains its shape because water moves in and out of the cell at equal rates.
24. What is active transport?
Answer: The movement of substances against their concentration gradient, requiring energy (ATP).
25. What is the main function of aquaporins in the plasma membrane?
Answer: To facilitate the movement of water molecules across the membrane.
26. What is the role of the plasma membrane in cell signaling?
Answer: It helps detect signals from the environment and communicate with other cells.
27. How does simple diffusion occur across the plasma membrane?
Answer: Molecules move from high to low concentration directly through the lipid bilayer.
28. What is the role of cholesterol in the plasma membrane?
Answer: It helps maintain the fluidity and stability of the membrane.
29. How do large molecules typically enter the cell?
Answer: Through endocytosis or via specific transport proteins.
30. What does the plasma membrane do in response to changes in the external environment?
Answer: It adjusts its permeability to maintain homeostasis and cell function.
These short questions and answers cover key concepts of plasma membrane structure and transport mechanisms, which are essential for understanding cell biology.
