IB Biology HL - Cell Membranes

Lipid Bilayer

Membrane barrier separating cell from surroundings.

Phospholipid

Amphipathic lipid forming bilayer structure.

Amphipathic Nature

Molecule having both hydrophilic and hydrophobic parts.

Hydrophobic

Repellent to water; non-polar region of bilayer.

Hydrophilic

Attracted to water; polar region of bilayer.

Micelle

Spherical arrangement of phospholipids in water.

Protocell

Primitive cell-like structure formed by lipid bilayers.

Plasma Membrane

Cell membrane surrounding cytoplasm; selectively permeable.

Selective Permeability

Regulation of molecule passage across the membrane.

Transport Proteins

Proteins facilitating movement of substances across membranes.

Compartmentalization

Separation of cellular processes into distinct areas.

Nutrient Accumulation

Cells concentrate nutrients beyond extracellular levels.

Electrical Potential

Charge difference across a membrane, crucial for neurons.

Integral Proteins

Membrane proteins spanning the lipid bilayer.

Peripheral Proteins

Membrane proteins associated with membrane surfaces.

Hydrophobic Interactions

Forces stabilizing integral proteins within the bilayer.

Enzymes in Membranes

Membrane-associated proteins speeding up metabolic reactions.

ATP Synthase

Integral protein generating ATP from ADP and phosphate.

Chemical Receptor Proteins

Membrane proteins receiving external chemical signals.

Acetylcholine Receptor

Protein responding to neurotransmitter acetylcholine.

Cytosol

Liquid component of the cytoplasm within cells.

Ribosomes

Cellular structures synthesizing proteins for membranes.

Vesicle

Transport structure delivering proteins to cell membranes.

Chemoreceptors

Sensory neurons detecting chemical stimuli.

Channels

Facilitated diffusion pathways for molecules.

Pumps

Active transport mechanisms requiring energy.

Recognition Proteins

Identify and interact with other cells.

Glycoproteins

Proteins with carbohydrate chains attached.

Adhesion Proteins

Facilitate cell adhesion to form tissues.

Cell Adhesion

Cells sticking to each other and ECM.

Extracellular Matrix (ECM)

Meshwork providing support and communication.

Cell Adhesion Molecules (CAMs)

Proteins forming junctions between cells.

Tight Junctions

Prevent leakage between closely packed cells.

Gap Junctions

Channels allowing efficient intercellular communication.

Adherens Junctions

Anchor cytoskeleton to plasma membrane.

Desmosomes

Strong junctions resisting mechanical stress.

Metastatic Cancer

Loss of adhesion allowing tumor spread.

Integrins

Anchorage proteins connecting cells to ECM.

Passive Transport

Movement without energy input across membranes.

Active Transport

Energy-requiring movement against concentration gradients.

Diffusion

Movement from high to low concentration.

Simple Diffusion

Passive transport of small, hydrophobic molecules.

Osmosis

Passive transport of water across membranes.

Equilibrium

Equal concentrations; no concentration gradient.

Gas Exchange

Oxygen and carbon dioxide movement via diffusion.

Aquaporin

Channel protein enhancing water permeability.

Facilitated Diffusion

Transport of large/polar molecules via channel proteins.

Channel Proteins

Proteins allowing specific molecule passage across membranes.

Gated Channels

Channel proteins that open/close in response to signals.

Voltage-Gated Channels

Open/close based on membrane electrical potential changes.

Ligand-Gated Channels

Open/close in response to chemical messenger binding.

Protein Pumps

Transport proteins requiring ATP for molecule movement.

Selectivity in Membrane Permeability

Membrane allows selective passage of substances.

Proton Pumps

Transport proteins crucial for photosynthesis and respiration.

Sodium-Potassium Pumps

Maintain action potentials in neurons by ion exchange.

Auxin Efflux Pumps

Establish concentration gradients for plant growth.

Gastric Proton Pump

Secretes hydrogen ions, increasing stomach acidity.

Proton Pump Inhibitors

Medications blocking proton pumps to reduce stomach acid.

Concentration Gradient

Difference in substance concentration across a membrane.

Hydrophobic Molecules

Substances that do not interact well with water.

Hydrophilic Molecules

Substances that interact well with water.

Cell Specialization

Differentiation of cells for specific functions.

Membrane Permeability

Ability of substances to cross the cell membrane.

Nonpolar molecules

Easily diffuse through membranes, e.g., O2, CO2.

Polar molecules

Diffuse slowly through membranes, e.g., H2O.

Saturation point

Maximum rate of facilitated diffusion due to protein limits.

ATP

Energy source for active transport processes.

Glycolipids

Lipids with carbohydrate chains for cell adhesion.

Cell-to-cell recognition

Allows immune cells to identify self vs. foreign cells.

ABO blood types

Determined by specific glycoproteins on red blood cells.

Glycocalyx

Layer formed by glycoproteins and glycolipids on membranes.

Fluid mosaic model

Dynamic membrane structure with diverse components.

Membrane asymmetry

Different compositions on extracellular and intracellular membrane faces.

Cell membrane fluidity

Ability to maintain flexible membrane structure.

Temperature effect on fluidity

Higher temperature increases membrane fluidity.

Unsaturated fatty acids

Lower melting points, enhance membrane fluidity.

Saturated fatty acids

Higher melting points, strengthen membranes at high temperatures.

Fatty acid tail length

Longer tails decrease fluidity due to increased interactions.

Vesicle formation

Membrane fusion during endocytosis and exocytosis.

Cell division

Ensures even distribution of membrane molecules.

Protein interactions

Crucial for cell signaling and communication.

Oligosaccharides

Short carbohydrate chains linked to proteins or lipids.

Membrane components

Include lipids, proteins, and carbohydrates.

Saturated chains

Fatty acid chains that pack tightly, reducing fluidity.

Unsaturated chains

Fatty acid chains with kinks, increasing membrane fluidity.

Cholesterol

Amphipathic molecule affecting membrane fluidity and permeability.

Endocytosis

Transport of molecules into the cell via vesicles.

Exocytosis

Transport of molecules out of the cell via vesicles.

Phagocytosis

Endocytosis where cells engulf and digest materials.

Pseudopods

Temporary projections used by amoeba for feeding.

Gated ion channels

Channel proteins that open/close in response to stimuli.

Nicotinic acetylcholine receptors

Ligand-gated channels requiring acetylcholine to open.

Depolarization

Process of membrane potential becoming more positive.

Repolarization

Restoration of resting membrane potential after depolarization.

Sodium-potassium pump

Transporter moving Na+ out and K+ into neurons.

Threshold potential

Membrane potential required to trigger action potential.

Action potential

Rapid change in membrane potential during neuron signaling.

Na+ influx

Rapid entry of sodium ions during depolarization.

K+ efflux

Outflow of potassium ions during repolarization.

Resting potential

Stable membrane potential before action potential occurs.