Biological Membranes Lecture Review

Flashcards covering the major functions, molecular components, properties like fluidity and selective permeability, and various transport mechanisms of biological membranes, derived from lecture notes.

Glycoprotein

A protein with carbohydrate chains attached, found in biological membranes.

Glycolipid

A lipid with carbohydrate chains attached, found in biological membranes.

Phospholipid Bilayer

The fundamental structure of biological membranes, consisting of two layers of phospholipids with hydrophobic tails facing inward and hydrophilic heads facing outward.

Integral Membrane Protein

A protein that partially or completely penetrates the phospholipid bilayer of a biological membrane.

Peripheral Membrane Protein

A protein that is loosely bound to the surface of the phospholipid bilayer of a biological membrane.

Cholesterol

A lipid component of biological membranes, acting as a fluidity buffer.

Amphipathic

A molecule that possesses both hydrophilic and hydrophobic properties, such as phospholipids and cholesterol.

Hydrophilic Head

The polar segment of a phospholipid molecule that faces the aqueous environment.

Hydrophobic Tails

The nonpolar hydrocarbon chains of a phospholipid molecule that face the interior of the bilayer.

Hydrophobic Core

The internal region of the phospholipid bilayer formed by the hydrophobic tails, acting as the main barrier to substance movement.

Saturated Fatty Acid Chain

A fatty acid chain lacking double bonds, resulting in a straight structure that favors tight packing and reduced membrane fluidity.

Unsaturated Fatty Acid Chain

A fatty acid chain with one or more double bonds, introducing kinks that reduce tight packing and increase membrane fluidity.

Fluid Mosaic Model

A model describing biological membranes as fluid structures where components (lipids, proteins) can move easily, forming a mosaic of various molecules.

Membrane Fluidity

The ease with which components of a biological membrane can move, affected by temperature, fatty acid saturation, fatty acid chain length, and cholesterol.

Selective Permeability

The property of the biological membrane that allows certain substances to pass while preventing others.

Passive Transport

Movement of substances across a membrane down their concentration gradient (from high to low concentration) without requiring cellular energy.

Active Transport

Movement of substances across a membrane against their concentration gradient (from low to high concentration), requiring cellular energy, typically ATP.

Diffusion

The tendency of a substance to spread out randomly in space due to kinetic energy.

Net Diffusion

The overall movement of a substance from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Osmosis

The passive diffusion of water across a selectively permeable membrane from a region of higher water concentration (lower solute) to a region of lower water concentration (higher solute).

Hypertonic

A solution that has a greater concentration of solute compared to another solution.

Hypotonic

A solution that has a lesser concentration of solute compared to another solution.

Isotonic

Solutions that have the same concentration of solute.

Simple Diffusion

Passive transport of small, nonpolar molecules directly across the lipid bilayer from high to low concentration without the help of membrane proteins.

Facilitated Diffusion

Passive transport of small or large uncharged polar molecules or ions down a concentration gradient using specific membrane proteins (channels or carriers), without requiring energy.

Channel Protein

A type of membrane protein that forms a hydrophilic pore through the membrane, allowing specific molecules or ions to pass via facilitated diffusion.

Aquaporin

A specific channel protein that facilitates the rapid transport of water molecules across cell membranes.

Carrier Protein

A type of membrane protein that binds to specific molecules and undergoes conformational changes to transport them across the membrane via facilitated diffusion or active transport.

Na+/K+/ATPase Pump

A primary active transport protein that uses ATP to pump 3 Na+ ions out of the cell and 2 K+ ions into the cell, against their concentration gradients, generating an electrochemical gradient.

Electrochemical Gradient

A gradient across a membrane that results from the combined effect of a difference in electrical charge and a difference in chemical concentration of ions.

Primary Active Transport

Active transport that directly uses energy (e.g., from ATP hydrolysis) to move substances against their concentration gradient.

Secondary Active Transport

Active transport that uses the energy stored in an existing electrochemical gradient (established by primary active transport) to move a different substance against its own concentration gradient.

Uniporter

A transporter protein that moves a single type of molecule across a membrane.

Symporter

A transporter protein that moves two different types of molecules in the same direction across a membrane.

Antiporter

A transporter protein that moves two different types of molecules in opposite directions across a membrane.

Endocytosis

A process by which cells take in large molecules, particles, or liquids by engulfing them in a vesicle formed from the plasma membrane; requires energy.

Phagocytosis

A type of endocytosis commonly referred to as 'cellular eating,' where a cell engulfs solid particles into a vesicle.

Pinocytosis

A type of endocytosis commonly referred to as 'cellular drinking,' where a cell takes in liquid substances and dissolved solutes through vesicles.

Exocytosis

A process by which cells release large molecules or waste products outside the cell by the fusion of vesicles with the plasma membrane; requires energy.