Skip to main content
뒤로

Membrane Structure and Function - General Biology

컨트롤 버튼이 '내비게이션' 모드로 변경되었습니다.
1/29

이 집합의 용어 (29)

  • What are the main components of cellular membranes?
    Lipids and proteins are the main components, with carbohydrates also playing an important role.
  • What is the structure of phospholipids in membranes?
    Phospholipids are amphipathic molecules with hydrophobic tails inside the bilayer and hydrophilic heads exposed to water.
  • Describe the fluid mosaic model of membrane structure.
    Membranes are a fluid mosaic of protein molecules bobbing in a fluid bilayer of phospholipids, with proteins often grouped by function.
  • How does temperature affect membrane fluidity?
    Membranes switch from fluid to solid as temperature cools; fluidity depends on lipid composition, with unsaturated fatty acids increasing fluidity.
  • What role does cholesterol play in membrane fluidity?
    Cholesterol reduces fluidity at moderate temperatures by restraining phospholipid movement and prevents solidification at low temperatures by disrupting packing.
  • What are the two major types of membrane proteins?
    Peripheral proteins are bound to the membrane surface, and integral proteins penetrate the hydrophobic core.
  • What functions do cell-surface membrane proteins perform?
    Functions include transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix.
  • How does HIV use membrane proteins to infect cells?
    HIV binds to the cell-surface protein CD4 and a co-receptor (CCR5 or CXCR4) to enter immune cells; lacking CCR5 confers resistance to some HIV strains.
  • What is selective permeability in membranes?
    Membranes allow some substances to cross more easily than others, regulating molecular traffic based on size, polarity, and transport proteins.
  • How do hydrophobic and hydrophilic molecules cross the lipid bilayer?
    Hydrophobic molecules cross rapidly by dissolving in the bilayer; hydrophilic molecules cross slowly or require transport proteins.
  • What are channel and carrier proteins?
    Channel proteins provide hydrophilic tunnels for molecules; carrier proteins bind and change shape to shuttle molecules across membranes.
  • What is osmosis?
    Osmosis is the diffusion of free water molecules across a selectively permeable membrane from low to high solute concentration.
  • Define isotonic, hypertonic, and hypotonic solutions relative to cells without walls.
    Isotonic: equal solute concentration; hypertonic: higher solute outside, causing water loss; hypotonic: lower solute outside, causing water gain and swelling.
  • How do cells without walls regulate water balance in hypotonic environments?
    They use osmoregulation mechanisms like contractile vacuoles to pump excess water out, preventing bursting.
  • What is turgor pressure in plant cells?
    Turgor pressure is the pressure exerted by the swollen cell against the inelastic cell wall, keeping the cell firm and healthy.
  • What happens to plant cells in hypertonic solutions?
    They lose water, shrink, and the membrane pulls away from the cell wall, a process called plasmolysis, causing wilting.
  • What is facilitated diffusion?
    Passive transport aided by transport proteins that speed the movement of molecules down their concentration gradients without energy use.
  • What are gated ion channels?
    Ion channels that open or close in response to stimuli such as electrical or chemical signals.
  • What distinguishes active transport from passive transport?
    Active transport uses energy, usually ATP, to move solutes against their concentration gradients via carrier proteins.
  • How does the sodium-potassium pump work?
    It uses ATP to pump Na+ out and K+ into the cell, maintaining concentration gradients essential for cell function.
  • What is membrane potential?
    The voltage difference across a membrane caused by unequal distribution of ions, influencing ion movement.
  • What is an electrogenic pump?
    A transport protein that generates voltage across a membrane by moving ions, storing energy for cellular work.
  • What is cotransport?
    Active transport of one solute indirectly drives the transport of another solute against its gradient via a coupled membrane protein.
  • How do plants use proton pumps and cotransporters?
    Proton pumps create an H+ gradient that cotransporters use to actively transport sucrose into cells.
  • What is bulk transport?
    The movement of large molecules across membranes via vesicles in processes called exocytosis and endocytosis.
  • Describe exocytosis.
    Transport vesicles fuse with the plasma membrane to release large molecules outside the cell.
  • What are the three types of endocytosis?
    Phagocytosis (cellular eating), pinocytosis (cellular drinking), and receptor-mediated endocytosis.
  • How does phagocytosis work?
    A cell engulfs particles by extending pseudopodia, enclosing them in a food vacuole that fuses with lysosomes for digestion.
  • What is receptor-mediated endocytosis?
    Vesicle formation triggered by solute binding to specific receptors clustered in coated pits, allowing selective uptake.