Cell Membranes - Structure and Function

Vocabulary flashcards covering key terms from the lecture notes on cell membranes.

Plasma membrane (plasmalemma)

Biological membrane separating the cell interior from the external environment; a thin layered structure visible under a microscope.

Edge (boundary of life)

The cell membrane is the boundary that defines the living cell.

Selective permeability

Property of membranes that allows some substances to cross more easily than others, enabling selective transport.

Cytoplasm

Site of most cellular reactions; the fluid inside the cell excluding the nucleus.

Genetic material

Information required for life; carries heredity (DNA or RNA).

Eukaryote

Organism with a membrane-bound nucleus and organelles.

Prokaryote

Organism lacking a membrane-bound nucleus; may have a nucleoid and other features like a capsule or flagellum.

Nucleus (membrane-bound)

Membrane-enclosed organelle that houses the cell’s genetic material.

Nucleolus

Nuclear substructure where ribosomal RNA is synthesized.

Mitochondrion

Organelle responsible for ATP production via cellular respiration.

Nucleoid

Region in prokaryotes where genetic material is located; not membrane-bound.

Ribosome

Ribonucleoprotein particle that synthesizes proteins.

Capsule

Outer protective layer present in some prokaryotes.

Flagellum

Structure used for cellular motility in many organisms.

Cell wall

Rigid layer outside the plasma membrane in some cells (e.g., bacteria and plants).

Fluid mosaic model

Dynamic membrane model: a fluid lipid bilayer with proteins embedded and able to move laterally.

Phospholipid

Amphipathic lipid with hydrophobic tails and a hydrophilic phosphate-containing head.

Glycolipid

Lipid linked to carbohydrate; contributes to membrane structure and cell recognition.

Glycoprotein

Protein with carbohydrate attached; involved in cell recognition and signaling.

Transmembrane protein (integral protein)

Protein that spans the lipid bilayer, often crossing the membrane entirely.

Peripheral protein

Protein loosely bound to the membrane surface, not embedded in the bilayer.

Cholesterol

Sterol in animal membranes that modulates fluidity and permeability; stabilizes the membrane.

Sterols

Ring-structured lipids (e.g., cholesterol in animals) that regulate membrane fluidity.

Amphipathic

Molecule having both hydrophobic and hydrophilic regions, enabling membrane organization.

Hydrophobic

Water-repelling, nonpolar region (the tails of phospholipids).

Hydrophilic

Water-attracting region (the heads of phospholipids).

Lipid bilayer

Two-layered arrangement of lipids forming the core structure of membranes.

Monolayer

Single layer of amphipathic molecules that can form on water surfaces.

Micelle

Spherical assembly of amphipathic lipids with tails inward and heads outward in water.

Gorter and Grendel

Dutch physiologists who proposed a bilayer membrane model based on lipid extraction.

Singer and Nicolson

Scientists who proposed the fluid mosaic model of membrane structure in 1972.