Components of the Cell: Plasma Membrane, Cytoskeleton, Cytoplasm, and Cell Wall

Vocabulary flashcards covering the structure and function of the plasma membrane, cytoskeleton, cytoplasm, and cell wall for General Biology 1 Lesson 1.2.

Plasma Membrane

The cell’s primary barrier composed mainly of a phospholipid bilayer that separates cytoplasm from the external environment.

Phospholipid

An amphipathic molecule with a hydrophilic phosphate head and two hydrophobic fatty-acid tails.

Phospholipid Bilayer

Two layers of phospholipids with heads facing outward and tails sandwiched inside, forming the structural basis of the plasma membrane.

Fluid Mosaic Model

Describes the plasma membrane as a dynamic, fluid structure with a mosaic of proteins, lipids, and sugars.

Selective Permeability

Property of the lipid bilayer that allows only certain molecules to pass while restricting others.

Cholesterol (Membrane)

Steroid molecule interspersed in the bilayer that modulates membrane fluidity.

Glycolipid

Lipid with a carbohydrate chain attached; contributes to cell recognition and membrane stability.

Glycoprotein

Protein with an attached carbohydrate chain; functions in cell–cell recognition and signaling.

Carrier Protein

Membrane protein that changes shape to transport specific substances across the membrane.

Channel Protein

Membrane protein forming a hydrophilic passageway that allows certain molecules or ions to diffuse through.

Receptor Protein

Membrane protein that binds specific signaling molecules to trigger cellular responses.

Cell Recognition Protein

Membrane glycoprotein that identifies a cell as self or non-self to the immune system.

Membrane Fluidity

Viscosity of the lipid bilayer influenced by fatty-acid kinks and cholesterol content.

Hydrophilic Head

Water-loving phosphate region of a phospholipid that faces aqueous environments.

Hydrophobic Tail

Water-repelling fatty-acid chains of a phospholipid located in the interior of the bilayer.

Cytoskeleton

Network of protein fibers (microtubules, microfilaments, intermediate filaments) providing support, shape, and motility.

Microtubule

Hollow tube made of α- and β-tubulin subunits; radiates from centrosomes and forms spindle fibers for chromosome movement.

Microfilament (Actin Filament)

Thin filament of actin protein that aids in cell shape changes and movement of cells and organelles.

Intermediate Filament

Stable rope-like fiber that maintains cell shape and anchors organelles, providing mechanical strength (e.g., in skin).

Centrosome

Microtubule-organizing center from which microtubules radiate.

Cytoplasm

Entire region between the plasma membrane and nucleus containing cytosol and suspended organelles.

Cytosol

Semifluid aqueous solution of water, ions, and organic molecules in which organelles are embedded.

Cell Wall

Rigid extracellular structure surrounding the plasma membrane, providing support and preventing lysis.

Peptidoglycan

Polymer of sugars and amino acids composing most bacterial cell walls.

Chitin

Nitrogen-containing polysaccharide forming the cell walls of many fungi.

Cellulose

Linear polysaccharide of β-glucose that makes up the primary component of plant cell walls.

Transport Protein

General term for membrane proteins (channel or carrier) that facilitate movement of substances across the membrane.

Lipid-Soluble Molecules

Small non-polar substances (e.g., O₂, CO₂) that can freely diffuse through the lipid bilayer.