Cell Structure and Function – Vocabulary Review

A comprehensive set of vocabulary flashcards covering cell types, membrane structure, organelles, cytoskeleton, cell walls, and other key concepts from the lecture notes.

Atom

Smallest unit of an element that retains the element’s chemical properties; ≈0.1 nm in diameter.

Protein

Polymer of amino acids that performs structural, catalytic and regulatory roles in cells.

Lipid

Hydrophobic biomolecule (fats, oils, phospholipids) important for membranes and energy storage.

Virus

Acellular infectious particle (≈10–100 nm) that requires host cells to replicate.

Bacterium

Single-celled prokaryote belonging to domain Bacteria; lacks membrane-bound nucleus.

Prokaryotic cell

Cell without a membrane-bound nucleus; domains Bacteria and Archaea.

Archaea

Domain of prokaryotes often living in extreme habitats; biochemically distinct from bacteria.

Eukaryotic cell

Cell with a membrane-bound nucleus, organelles, and larger size than prokaryotes.

Domain Eukarya

Taxonomic domain that includes protists, fungi, plants, and animals.

Organelle

Membrane-bound or specialized sub-compartment performing a specific cellular function.

Endomembrane system

Interacting organelles (ER, Golgi, vesicles, plasma membrane, etc.) connected by membranes or vesicles.

Energy-related organelles

Mitochondria and chloroplasts; generate ATP or carry out photosynthesis.

Surface area-to-volume ratio

Relationship that limits cell size; higher ratio favors efficient exchange with environment.

Light microscope

Instrument using visible light to magnify objects up to ≈1 µm resolution.

Electron microscope

Microscope using electron beams; resolution down to ≈0.1 nm.

Plasma membrane

Phospholipid bilayer with proteins that defines cell boundary and regulates transport.

Selective permeability

Property of membranes to allow some substances to cross more easily than others.

Phospholipid bilayer

Two layers of phospholipids with hydrophilic heads outward and hydrophobic tails inward.

Membrane protein

Protein embedded in or attached to membrane; functions as enzyme, transporter, receptor, or marker.

Fluid mosaic model

Singer & Nicolson (1972) concept: proteins embedded in a fluid lipid bilayer.

Davson–Danielli model

Older membrane model proposing protein layers coating both sides of a lipid bilayer.

Gorter & Grendel

Researchers (1925) who first proposed the lipid bilayer nature of biological membranes.

Hydrophilic head

Water-loving phosphate-containing part of a phospholipid.

Hydrophobic tail

Water-repelling fatty-acid portion of a phospholipid.

Nucleus

Membrane-bound control center of eukaryotic cells housing DNA.

Nuclear envelope

Double membrane surrounding the nucleus, containing nuclear pores.

Nuclear pore

Protein-lined channel permitting exchange of molecules between nucleus and cytoplasm.

Nucleoplasm

Semifluid interior matrix of the nucleus containing chromatin and nucleolus.

Chromatin

DNA-protein complex that condenses into chromosomes during cell division.

Chromosome

Discrete, highly condensed chromatin structure visible during mitosis or meiosis.

Nucleolus

Dense nuclear region that assembles ribosomal RNA and ribosome subunits.

Mitochondrion

Double-membraned organelle where cellular respiration produces ATP; contains DNA & ribosomes.

Crista (plural cristae)

Fold of the inner mitochondrial membrane increasing surface area for respiration enzymes.

Matrix (mitochondrial)

Internal fluid of mitochondrion containing enzymes, DNA, and ribosomes.

Chloroplast

Photosynthetic plastid in plants/algae containing chlorophyll, thylakoids, and its own DNA.

Thylakoid

Flattened membrane sac inside chloroplast where light reactions of photosynthesis occur.

Granum

Stack of thylakoids within a chloroplast.

Stroma

Fluid surrounding thylakoids in chloroplast; site of Calvin cycle reactions.

Leucoplast

Colorless plastid that synthesizes and stores starch, oils, or proteins.

Chromoplast

Plastid containing red, orange, or yellow pigments in flowers and ripe fruits.

Ribosome

RNA-protein organelle that reads mRNA to synthesize polypeptides; composed of large and small subunits.

Free ribosome

Ribosome suspended in cytosol, producing cytoplasmic proteins.

Bound ribosome

Ribosome attached to rough ER, synthesizing secretory or membrane proteins.

Endoplasmic reticulum (ER)

Network of membranous tubules and sacs (cisternae) continuous with nuclear envelope.

Rough ER (RER)

ER studded with ribosomes; site of protein synthesis and initial modification.

Smooth ER (SER)

ER lacking ribosomes; synthesizes lipids, detoxifies poisons, stores Ca²⁺.

Cisternae

Flattened membrane sacs forming ER and Golgi compartments.

Golgi body (dictyosome)

Stack of flattened membranes that modify, package, and sort proteins and polysaccharides.

Golgi apparatus

Collective term for all Golgi bodies within a cell.

Vesicle

Small membrane-bound sac used to transport substances within or outside the cell.

Vacuole

Large membrane-bound sac storing water, ions, pigments, and wastes; prominent in plant cells.

Central vacuole

Large vacuole in mature plant cells that maintains turgor pressure and stores metabolites.

Cytoskeleton

Dynamic network of protein fibers (microtubules, microfilaments, intermediate filaments) providing cell shape and movement.

Microtubule

Hollow tubulin cylinder involved in organelle movement, spindle formation, cilia and flagella.

Microfilament (actin filament)

Thin actin fiber responsible for cell motility and cytoplasmic streaming.

Intermediate filament

Sturdy cytoskeletal fiber providing mechanical strength and shape stability.

Cell wall

Rigid structure outside plasma membrane of plants, algae, fungi, and bacteria; provides support.

Cellulose

β-1,4-linked glucose polysaccharide forming strong fibers in plant cell walls.

Pectin

Polysaccharide that cements adjacent plant cell walls in the middle lamella.

Primary cell wall

Thin, flexible wall secreted by growing plant cells.

Secondary cell wall

Stronger, multilayered wall deposited inside the primary wall after growth ceases.

Lignin

Hard, complex polymer that strengthens secondary cell walls.

Middle lamella

Pectin-rich layer binding the primary walls of adjacent plant cells.

Plasmodesma (plural plasmodesmata)

Cytoplasmic channel through plant cell walls allowing intercellular communication.

Cell signaling

Process by which cells communicate using chemical signals or direct connections.

Lysosome

Animal-cell vesicle containing hydrolytic enzymes for digestion and recycling (autophagy).

Autophagy

Lysosome-mediated degradation of damaged organelles within the cell.

Centrosome

Microtubule-organizing center in eukaryotic cells; contains a pair of centrioles in animals.

Centriole

Cylindrical microtubule structure aiding animal cell division.

Peroxisome

Membrane-bound organelle with oxidative enzymes that break down fatty acids and detoxify peroxide.

Cilium (plural cilia)

Short, numerous motile extension of cell membrane containing 9+2 microtubule arrangement.

Flagellum (plural flagella)

Long, whip-like cellular appendage used for locomotion; shares 9+2 microtubule axoneme.

Axoneme

Core of cilium/flagellum composed of microtubule doublets and central pair.

Basal body

Organelle at base of cilium/flagellum structurally similar to a centriole.

Capsule (prokaryote)

Gelatinous outer covering of some bacteria offering protection and adhesion.

Pilus (plural pili)

Short bacterial surface appendage used for attachment or DNA transfer.

Nucleoid

Irregularly shaped region in prokaryotes where the circular DNA is located.

Transport protein

Membrane protein that facilitates movement of substances across the bilayer.

Receptor protein

Membrane protein that binds specific signaling molecules, triggering cellular responses.

Enzyme (membrane-bound)

Catalytic protein embedded in the membrane, accelerating specific reactions at the surface.

Cell-surface marker

Glycoprotein or glycolipid identifying cell type and mediating recognition.

Phospholipid

Amphipathic molecule with glycerol backbone, two fatty acids, and a phosphate group.

Nanometer (nm)

Unit of length equal to 10⁻⁹ m; used to measure molecules and viruses.

Micrometer (µm)

Unit of length equal to 10⁻⁶ m; common measure for cells and organelles.

Autotroph (photosynthetic)

Organism (e.g., green plant) that produces organic molecules from CO₂ using light energy.

Cellular respiration

Metabolic pathway in mitochondria converting glucose to CO₂, H₂O, and ATP.

Cytoplasmic streaming

Actin-driven movement of cytoplasm distributing materials within large plant cells.

Spindle apparatus

Microtubule structure that segregates chromosomes during cell division.

Desmotubule

Narrow tube of ER that traverses plasmodesmata connecting neighbouring plant cells.

Endosymbiotic theory

Concept that mitochondria and chloroplasts evolved from free-living prokaryotes engulfed by ancestral eukaryotes.

Primary plastid

Ancestral plastid (e.g., chloroplast) derived directly from cyanobacterial endosymbiosis.

Autocrine signal

Chemical messenger that acts on the same cell that secreted it.

Hydrolytic enzyme

Enzyme that breaks chemical bonds using water, common in lysosomes.

Turgor pressure

Pressure of the central vacuole against the plant cell wall, maintaining rigidity.

Cisternae (Golgi)

Flattened, membrane-bound sacs forming individual units of a Golgi body.

Trans face (Golgi)

‘Shipping’ side of Golgi apparatus where vesicles bud off.

Cis face (Golgi)

‘Receiving’ side of Golgi apparatus facing the ER.