Life Sciences 11 – Unit B: Organisms Are Cellular

Vocabulary flashcards summarizing essential cell-biology terms, structures, and processes from Unit B lecture notes.

Cell

The basic structural and functional unit of all living things, consisting of a membrane-bound protoplasm.

Cell Theory

States that all organisms are composed of cells, cells are the fundamental building blocks, and all cells arise from pre-existing cells (Schleiden, Schwann, Virchow).

Prokaryotic Cell

A cell lacking a nucleus and internal membranous organelles; characteristic of bacteria and archaea.

Eukaryotic Cell

A cell that possesses a true nucleus and various membrane-bound organelles.

Compartmentalization

The division of a eukaryotic cell into membrane-bound spaces, allowing simultaneous, efficient metabolic reactions.

Organelle

A specialized intracellular structure surrounded by membrane(s) that performs a distinct function.

Nucleus

Porous, double-membrane organelle housing DNA and nucleolus; the cell’s control centre.

Cytoplasm

The aqueous interior of a cell containing ions, molecules, and organelles where metabolism occurs.

Protoplasm

The living part of a cell—its cell membrane plus everything enclosed by it.

Cell Membrane

Phospholipid-protein boundary regulating movement of materials into and out of the cytoplasm.

Cell Wall

Rigid carbohydrate-based layer (cellulose in plants, chitin in fungi) external to the membrane that supports certain cells.

Endocytosis

Active process by which a cell engulfs external particles, forming an internal vesicle or food vacuole.

Food Vacuole

Membrane-bound sac formed during endocytosis that encloses ingested particles for digestion.

Microvilli

Minute membrane extensions that increase cell surface area for absorption.

Autotroph

An organism or cell that manufactures its own nutrients from inorganic sources using environmental energy.

Photosynthetic Autotroph

An autotroph that uses light energy and chlorophyll to build glucose from CO₂ and water.

Heterotroph

An organism or cell that obtains nutrients by ingesting or absorbing them from the environment.

Chloroplast

Double-membrane organelle in plant cells where photosynthesis occurs; contains chlorophyll.

Chlorophyll-a

Primary photosynthetic pigment that absorbs red and blue light while reflecting green.

Mitochondrion

Double-membrane organelle with highly folded inner membrane; site of aerobic respiration and ATP production—“powerhouse of the cell.”

Rough Endoplasmic Reticulum (RER)

Membranous channel studded with ribosomes; synthesizes and transports proteins.

Smooth Endoplasmic Reticulum (SER)

Membranous channel lacking ribosomes; synthesizes lipids, detoxifies chemicals, and forms transport vesicles.

Golgi Bodies (Golgi Apparatus)

Flattened membranous saccules that modify, package, and sort cellular products into vesicles; produce lysosomes.

Lysosome

Enzyme-filled vesicle responsible for intracellular digestion of worn-out structures and food molecules.

Vacuole

Large membrane-bound sac for storage of food, wastes, or cell products; central in plant cells, contractile in some protists.

Vesicle

Small membrane-bound compartment that transports or stores substances within a cell.

Cytoskeleton

Network of microtubules and microfilaments providing structural support and enabling movement inside cells.

Microtubule

Tubulin-based cylindrical fibre; forms cilia, flagella, and internal scaffolding.

Microfilament (Actin)

Thin protein filament that, when activated (e.g., by Ca²⁺), slides to change cell shape or move components.

Cilia

Short, numerous microtubule-based projections that beat rhythmically to move a cell or fluid over its surface.

Flagella

Long, usually few microtubule-based projections that propel certain cells through fluid.

ATP (Adenosine Triphosphate)

Universal energy currency produced mainly in mitochondria during cellular respiration.

Ribosome

Small structure composed of rRNA and proteins that assembles amino acids into polypeptides according to mRNA instructions.

Chromosome

DNA molecule with associated proteins containing genetic information; visible during cell division.

Gene

Functional segment of DNA that encodes information for making a specific protein or RNA product.