Chapter 8 Flashcards
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What are the core components of biological membranes?
Biological membranes are primarily composed of lipids and proteins, with carbohydrates also playing a crucial role.
What is the structure of phospholipids in the membrane?
Phospholipids are amphipathic molecules with hydrophilic heads facing aqueous compartments and hydrophobic tails shielded internally, forming a stable bilayer.
What are integral and peripheral proteins in the membrane?
Integral proteins penetrate the lipid bilayer, with some spanning the entire bilayer (transmembrane proteins). Peripheral proteins are loosely attached to the membrane surface and may connect to the cytoskeleton or extracellular matrix.
What is the fluid mosaic model of the membrane?.
The fluid mosaic model describes the membrane as a fluid structure with lipids and proteins moving laterally, driven by weak hydrophobic interactions
How does temperature affect membrane fluidity?
Decreasing temperatures cause membranes to solidify, while unsaturated phospholipids enhance fluidity. Cholesterol acts as a fluidity buffer, restraining movement at high temperatures and preventing solidification at low temperatures.
What is the role of membrane carbohydrates?
Membrane carbohydrates function in cell recognition, essential for immune response, organ development, and blood-type specificity. They are usually glycoproteins or glycolipids.
What is selective permeability in biological membranes?
Selective permeability allows membranes to regulate molecular traffic, permitting some substances to pass more easily than others, ensuring controlled exchange with the environment.
What is passive transport and how does it work?
Passive transport involves the movement of molecules down their concentration gradient without energy input, achieving equilibrium. Examples include simple diffusion and facilitated diffusion.
What is osmosis and how does it affect cells?
Osmosis is the diffusion of water across a selectively permeable membrane, balancing solute concentrations. It affects cells by causing them to swell in hypotonic solutions, shrink in hypertonic solutions, or remain stable in isotonic solutions.
What are the types of transport proteins involved in facilitated diffusion?
Channel proteins create hydrophilic tunnels for specific ions or molecules, while carrier proteins bind solutes, undergo conformational changes, and shuttle them across the membrane.
What is active transport and how does it differ from passive transport?
Active transport requires energy to move solutes against their concentration gradients, allowing cells to maintain specific internal environments. It involves transport proteins like the sodium-potassium pump.
What is the sodium-potassium pump and its function?
The sodium-potassium pump is an active transport mechanism that cycles to export 3 Na+ ions and import 2 K+ ions, contributing to the membrane potential and maintaining ion gradients.
What is membrane potential and how is it generated?
Membrane potential is the electrical potential energy resulting from the uneven distribution of ions across a membrane, typically negative inside the cell. It is generated by ion gradients and electrogenic pumps.
What is cotransport and how does it work?
Cotransport links the transport of one solute against its gradient to the diffusion of another solute down its gradient, leveraging energy indirectly. An example is proton-sucrose cotransport in plants.
What are exocytosis and endocytosis?
Exocytosis involves the secretion of molecules when vesicles fuse with the plasma membrane. Endocytosis is the process by which cells internalize molecules by engulfing them in vesicles, occurring in forms like phagocytosis, pinocytosis, and receptor-mediated endocytosis.
What is the role of cholesterol in membrane fluidity?
Cholesterol acts as a fluidity buffer, restraining movement at high temperatures and preventing solidification at low temperatures.
How do unsaturated phospholipids affect membrane fluidity?
Unsaturated phospholipids enhance membrane fluidity due to kinks in their tails that prevent tight packing.
What is the function of glycoproteins and glycolipids in the membrane?
Glycoproteins and glycolipids function in cell recognition, which is essential for immune response, organ development, and blood-type specificity.
What is the difference between isotonic, hypertonic, and hypotonic solutions?
Isotonic: No net water movement; cell volume remains stable.
Hypertonic: Water exits the cell, causing it to shrivel.
Hypotonic: Water enters the cell, causing it to swell and potentially burst.
What are aquaporins and their function?
Aquaporins are channel proteins that facilitate the rapid transport of water molecules across the cell membrane.
What is the sodium-potassium pump and its significance?
The sodium-potassium pump is an active transport mechanism that exports 3 Na+ ions and imports 2 K+ ions, contributing to the membrane potential and maintaining ion gradients.
What is membrane potential?
Membrane potential is the electrical potential energy resulting from the uneven distribution of ions across a membrane, typically negative inside the cell.
What is cotransport and give an example?
Cotransport links the transport of one solute against its gradient to the diffusion of another solute down its gradient. Example: Proton-sucrose cotransport in plants.
What are the three forms of endocytosis?
Phagocytosis: Engulfing large particles.
Pinocytosis: Ingesting extracellular fluid.
Receptor-Mediated Endocytosis: Selective uptake of molecules via receptors.
How do exocytosis and endocytosis contribute to membrane maintenance?
Exocytosis adds vesicle membranes to the plasma membrane, while endocytosis removes membrane segments, balancing membrane size in non-growing cells.
