SL & HL Biology: Key Terms (Cell Biology)

Vocabulary flashcards covering essential SL & HL terms related to cell biology.

Cell

The basic unit of life; the smallest unit that can carry out life processes.

Cell Theory

Fundamental principle that all living organisms are composed of cells, cells arise from pre-existing cells, and the cell is the basic unit of life.

Microscope

An instrument used to magnify small objects, enabling visualization of cells and their parts.

Magnification

The ratio by which an object's image size is larger than its real size.

Scale bar

A marked line on an image indicating a real-world distance to gauge size.

Resolution

The ability to distinguish two close objects as separate; higher resolution means finer detail.

Electron microscope

A microscope that uses electron beams to achieve high resolution (TEM and SEM).

DNA

Deoxyribonucleic acid; the molecule that stores genetic information.

Cytoplasm

The jelly-like interior of the cell, excluding the nucleus, where many metabolic processes occur.

Plasma membrane

The phospholipid bilayer surrounding a cell, regulating movement of substances in and out.

Nucleoid region

Region in prokaryotic cells where the circular DNA chromosome is located; not membrane-bound.

Prokaryote

Organism whose cells lack a membrane-bound nucleus.

Eukaryote

Organism whose cells have a true nucleus and membrane-bound organelles.

Metabolism

All chemical reactions in a cell or organism that sustain life.

Ribosome

Small particle where protein synthesis occurs; found free in cytoplasm or on rough ER.

Nucleus

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

Chromosome

Structure containing DNA; in eukaryotes linear and associated with histones; in prokaryotes usually circular.

Sister chromatids

Two identical copies of a chromosome held together at the centromere until mitosis.

Histone protein

Proteins around which DNA winds to form chromatin, aiding DNA packaging.

Organelle

Specialized subcellular structure with a specific function.

Mitochondrion

Organelle that generates ATP through cellular respiration; the cell’s powerhouse.

Rough endoplasmic reticulum

ER with ribosomes; synthesizes and processes proteins.

Smooth endoplasmic reticulum

ER lacking ribosomes; synthesizes lipids and detoxifies compounds.

Golgi apparatus

Stack of membranes that modifies, sorts, and ships proteins and lipids.

Vacuole

Membrane-bound storage sac; plant cells have a large central vacuole; animals have smaller ones.

Lysosome

Organelle containing digestive enzymes for breaking down waste materials.

Cytoskeleton

Network of protein filaments giving cell shape, organization, and movement.

Unicellular

Organism composed of a single cell.

Multicellular

Organism composed of many specialized cells.

Homeostasis

Maintenance of a stable internal environment despite external changes.

Nutrition

Process by which organisms obtain and utilize nutrients.

Movement

Ability of cells or organisms to move, or of substances within cells to move.

Growth

Increase in size or number of cells.

Response to stimuli

Ability to detect and respond to environmental changes.

Reproduction

Production of offspring; can be asexual or sexual.

Plastids

Family of organelles in plant cells; includes chloroplasts and related structures.

Chloroplasts

Plastids that carry out photosynthesis; contain chlorophyll.

Centrioles

Cylindrical structures near the nucleus that organize spindle fibers during cell division (mostly in animal cells).

Fungal hyphae

Thread-like filaments that make up the body of a fungus; form a mycelium.

Aseptate

Hyphae lacking septa (cell walls) that divide cells; continuous cytoplasm.

Cell wall

Rigid layer outside the plasma membrane; cellulose in plants, chitin in fungi.

Microvilli

Small finger-like projections that increase surface area for absorption.

Sap vacuole

Vacuole containing cell sap in plant cells; stores ions and maintains turgor.

Flagellum

Long, whip-like structure that enables cell movement in some cells.

Cilia

Short, numerous projections that beat to move fluid or the cell.

Cellulose

Polysaccharide; main component of plant cell walls.

Peptidoglycan

Mesh-like layer forming bacterial cell walls, providing rigidity.

Pilus

Short, hair-like appendage on bacteria used for attachment and DNA transfer.