Cell Membrane Structure & Function Flashcards
Define aqueous solution.
A solution where water is the solvent (e.g., saltwater, cytoplasm).
Define hypertonic, hypotonic, and isotonic.
Hypertonic – Higher solute concentration outside the cell; water leaves the cell.
Hypotonic – Lower solute concentration outside the cell; water enters the cell.
Isotonic – Equal solute concentration; no net water movement.
Define diffusion and osmosis.
Diffusion – Movement of molecules from high to low concentration.
Osmosis – Diffusion of water across a semipermeable membrane.
Define free water molecules and hydration.
Free water molecules – Water molecules not bound to solutes, available for osmosis.
Hydration – Water molecules surround solutes, forming a hydration shell.
Define concentration gradient and osmolarity.
Concentration gradient – A difference in solute concentration across a membrane.
Osmolarity – The total solute concentration in a solution.
Compare and contrast the effects of placing an animal cell vs. a plant cell in pure water.
Animal cell – Swells and lyses (bursts) due to excessive water intake.
Plant cell – Becomes turgid (firm) as the cell wall prevents bursting
Describe the fluid-mosaic model of cell membranes.
Membrane is a flexible bilayer of phospholipids with embedded proteins.
Describe the role of phospholipids in cell membranes.
Form a bilayer with hydrophobic tails inside and hydrophilic heads outside.
Allow fluidity and act as a barrier to most molecules.
Describe the role of carbohydrates in cell membranes.
Functions: Cell recognition, signaling, and protection (e.g., blood types).
List four roles of membrane proteins.
- Transport – Channels (e.g., aquaporins), carriers (e.g., glucose transporter).
- Enzymatic activity – Catalyze reactions (e.g., ATP synthase).
- Signal transduction – Receive signals (e.g., insulin receptor).
- Cell recognition & adhesion – Immune system markers, tight junctions.
Describe the function of Glucose-6-phosphatase in liver cells.
• Found in the smooth ER of liver cells.
• Converts glucose-6-phosphate → glucose, allowing glucose release into blood.
• Crucial for blood sugar regulation.
Give examples of a channel protein and a carrier protein for facilitated diffusion.
• Channel protein: Aquaporins (water transport).
• Carrier protein: GLUT-1 (glucose transporter).
Explain how the absence of chloride channels causes cystic fibrosis.
• CFTR protein (chloride channel) is defective.
• Cl⁻ ions cannot exit cells, leading to thick mucus buildup in lungs and pancreas.
Distinguish between simple diffusion, facilitated diffusion, and active transport.
• Simple diffusion: No energy, small nonpolar molecules cross (O₂, CO₂).
• Facilitated diffusion: No energy, uses proteins (e.g., glucose transporter).
• Active transport: Requires ATP, moves molecules against gradient (Na⁺/K⁺ pump).
Define saturation in membrane transport.
• Occurs when all transport proteins are in use, limiting the rate of transport.
• Facilitated diffusion and active transport plateau at high solute concentration.
