Chapter 3 – Cells and Their Functions (Vocabulary)

These vocabulary flashcards cover the principal terms from Chapter 3, including cell structure, membrane transport, protein synthesis, cell division, and cancer concepts. Use them to master key definitions before your exam.

Cytology

The scientific study of cells.

Cell

The basic unit of life that exhibits organization, metabolism, responsiveness, homeostasis, growth, and reproduction.

Compound light microscope

A laboratory microscope that uses visible light and lenses to magnify specimens; most common in teaching labs.

Transmission electron microscope (TEM)

Microscope that passes an electron beam through ultra-thin sections to reveal fine internal cell structures.

Scanning electron microscope (SEM)

Microscope that sweeps electrons across a specimen’s surface to produce detailed three-dimensional images.

Plasma membrane

The phospholipid bilayer with proteins and cholesterol that encloses cell contents and controls passage of substances.

Phospholipid bilayer

Double layer of phospholipid molecules forming the fundamental structure of the plasma membrane.

Cholesterol (membrane)

Steroid lipid embedded in the bilayer that stabilizes membrane fluidity and integrity.

Channel protein

Membrane protein that forms a pore allowing specific ions or water-soluble molecules to cross.

Transporter (carrier) protein

Membrane protein that changes shape to shuttle substances such as glucose across the membrane.

Receptor protein

Membrane protein that binds hormones or other ligands and initiates a cellular response.

Enzyme (membrane-bound)

Protein catalyst located at the membrane surface, accelerating chemical reactions.

Linker protein

Plasma-membrane protein that stabilizes the membrane and attaches adjacent cells together.

Cell identity marker

Unique membrane protein (often a glycoprotein) that acts as a molecular ‘name tag’ for immune recognition.

Cytoplasm

All material between the nuclear envelope and plasma membrane, including cytosol and organelles.

Cytosol

The fluid portion of the cytoplasm containing water, enzymes, ions, and nutrients.

Nucleus

The largest organelle; surrounded by a nuclear membrane and houses chromosomes and the nucleolus.

Nuclear membrane

Double membrane with pores that encloses the nucleus and regulates nuclear-cytoplasmic exchange.

Chromosome

DNA-protein structure carrying hereditary information; visible during cell division.

Gene

A segment of DNA that contains the code for one protein (or functional RNA).

DNA (deoxyribonucleic acid)

Double-stranded helix of nucleotides that stores hereditary information and directs protein synthesis.

RNA (ribonucleic acid)

Single-stranded nucleic acid that participates in translating genetic information into proteins.

Messenger RNA (mRNA)

RNA transcribed from DNA that carries the genetic code to ribosomes.

Ribosomal RNA (rRNA)

RNA that, with protein, forms ribosomes—the sites of protein assembly.

Transfer RNA (tRNA)

RNA molecule that delivers specific amino acids to the ribosome during translation.

Ribosome

Small RNA-protein complex (free or on rough ER) that links amino acids to build proteins.

Endoplasmic reticulum (ER)

Network of membranous channels; rough ER bears ribosomes, smooth ER does not.

Rough ER

Endoplasmic reticulum with ribosomes; modifies, folds, and sorts newly made proteins.

Smooth ER

Endoplasmic reticulum without ribosomes; synthesizes lipids and detoxifies chemicals.

Golgi apparatus

Stacked membrane sacs that modify, sort, and package proteins for transport.

Mitochondrion

Organelle with folded inner membrane (cristae) that converts nutrients into ATP; the cell’s powerhouse.

Lysosome

Membrane sac containing digestive enzymes that break down waste and foreign material.

Peroxisome

Organelle containing enzymes that neutralize harmful substances like hydrogen peroxide.

Proteasome

Barrel-shaped protein complex that degrades improperly formed or damaged proteins.

Vesicle

Small membrane-bound sac for storage, transport, or secretion of materials.

Centrioles

Paired rod-shaped bodies that organize the mitotic spindle during cell division.

Microvilli

Short plasma-membrane extensions that greatly increase surface area for absorption.

Cilia

Short, hairlike surface projections that move fluids across the cell surface.

Flagellum

Long, whip-like extension that propels a cell; present in human sperm cells.

Diffusion

Passive movement of particles from higher to lower concentration down the gradient.

Facilitated diffusion

Passive transport of substances across membranes via channels or carrier proteins.

Osmosis

Diffusion of water through a semipermeable membrane toward higher solute concentration.

Filtration

Movement of materials through a membrane driven by a pressure gradient.

Isotonic solution

Fluid with solute concentration equal to the cytoplasm; causes no net water change.

Hypotonic solution

Fluid with lower solute concentration than the cytoplasm; cell swells as water enters.

Hemolysis

Rupture of red blood cells, often due to placement in a hypotonic solution.

Hypertonic solution

Fluid with higher solute concentration than the cytoplasm; cell loses water and shrinks.

Crenation

Shriveling of red blood cells in a hypertonic environment.

Active transport

ATP-dependent movement of substances against their concentration gradient via pumps.

Vesicular transport

Energy-requiring bulk movement of materials in or out of the cell using vesicles.

Endocytosis

Vesicular process that moves materials into the cell.

Phagocytosis

"Cell eating"; endocytosis of large particles such as bacteria.

Pinocytosis

"Cell drinking"; endocytosis of fluid droplets.

Exocytosis

Vesicular process that releases materials from the cell to the exterior.

ATP (adenosine triphosphate)

High-energy molecule that powers cellular activities, including active transport.

Selective permeability

Property of the plasma membrane that allows some substances to cross more easily than others.

Interphase

Cell-cycle phase of growth and DNA replication preceding mitosis.

Mitosis

Division of a somatic cell nucleus producing two genetically identical daughter nuclei.

Prophase

First mitotic stage; chromosomes condense, spindle forms, nuclear envelope disappears.

Metaphase

Mitotic stage in which chromosomes line up at the cell’s equator.

Anaphase

Mitotic stage where sister chromatids separate and move to opposite poles.

Telophase

Final mitotic stage; nuclear membranes re-form and cytokinesis begins.

Cytokinesis

Division of the cytoplasm resulting in two separate daughter cells.

Meiosis

Cell division that produces gametes with half the normal chromosome number.

DNA replication

Copying of DNA during interphase so each daughter cell receives identical genetic material.

Mutation

Any change in the DNA nucleotide sequence.

Cancer

Disease characterized by uncontrolled cell division and potential metastasis.

Carcinogen

Physical, chemical, or biological agent that causes cancer.

Metastasis

Spread of cancer cells from the original site to distant tissues.

Tumor

Mass of abnormal cells resulting from uncontrolled proliferation; may be benign or malignant.

Apoptosis

Programmed cell death that removes damaged or unnecessary cells.

Free radical

Highly reactive molecule with unpaired electrons that can damage cellular components.

Micrometer (µm)

Unit of length (one-millionth of a meter) used to measure cell size and structures.