The Fundamental Unit of Life – Vocabulary Review

Vocabulary flashcards covering key terms and concepts from the lecture on cell structure, function, and organization.

Cell

Basic structural and functional unit of life; first observed by Robert Hooke and named from the Latin for “little room.”

Robert Hooke

English scientist who, in 1665, coined the term “cell” after viewing cork under a self-designed microscope.

Unicellular organism

A living being made of a single cell, e.g., Amoeba, Chlamydomonas, Paramoecium, bacteria.

Multicellular organism

Organism composed of many specialized cells that work together, such as plants, fungi, and animals.

Cell theory

Concept stating all living things are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Plasma membrane (Cell membrane)

Thin, flexible outer boundary of a cell that regulates movement of substances in and out; made of lipids and proteins.

Selectively permeable membrane

A membrane that allows certain molecules to pass while restricting others; characteristic of the plasma membrane.

Diffusion

Passive movement of particles from a region of high concentration to one of lower concentration until equilibrium is reached.

Osmosis

Diffusion of water through a selectively permeable membrane toward a region of higher solute concentration.

Hypotonic solution

External solution with higher water (lower solute) concentration than the cell, causing the cell to swell as water enters.

Isotonic solution

Solution with the same water concentration as the cell; results in no net movement of water and no change in cell size.

Hypertonic solution

Solution with lower water (higher solute) concentration than the cell, causing the cell to shrink as water leaves.

Endocytosis

Energy-requiring process in which the plasma membrane engulfs material, bringing it into the cell.

Cell wall

Rigid outer layer found in plant, fungal, and bacterial cells; in plants chiefly composed of cellulose and providing structural strength.

Plasmolysis

Shrinkage of cell contents away from the cell wall when a plant cell loses water by osmosis.

Nucleus

Membrane-bound organelle containing chromosomes; controls cellular activities and reproduction.

Nuclear membrane

Double-layered membrane with pores surrounding the nucleus, regulating exchange with cytoplasm.

Chromosome

Condensed, rod-shaped DNA–protein structure visible during cell division; carries hereditary information.

DNA (Deoxyribonucleic acid)

Molecule storing genetic information necessary for constructing and organizing cells.

Gene

Functional segment of DNA that codes for a specific protein or trait.

Nucleoid

Poorly defined, membrane-less nuclear region in a prokaryotic cell containing DNA.

Prokaryote

Organism whose cells lack a true nucleus and membrane-bound organelles, e.g., bacteria.

Eukaryote

Organism whose cells have a true nucleus and membrane-bound organelles, e.g., plants and animals.

Cytoplasm

Semi-fluid substance inside the plasma membrane, containing organelles and site of many metabolic reactions.

Organelle

Membrane-bound subcellular structure that performs a specific function within the cell.

Endoplasmic reticulum (ER)

Network of membrane-bound tubules/sacs involved in transport and synthesis of proteins and lipids.

Rough endoplasmic reticulum (RER)

ER region studded with ribosomes; synthesises and transports proteins.

Smooth endoplasmic reticulum (SER)

ER region without ribosomes; synthesises lipids and detoxifies poisons/drugs.

Membrane biogenesis

Formation of new cellular membranes from proteins and lipids produced mainly in the ER.

Golgi apparatus

Stack of membrane-bound cisternae that modifies, sorts, and packages substances into vesicles for transport.

Lysosome

Membrane-bound vesicle containing digestive enzymes that break down foreign material and worn-out organelles.

Suicide bags

Nickname for lysosomes because rupturing them releases enzymes that can destroy their own cell.

Mitochondrion

Double-membraned organelle with inner folds (cristae) that generate ATP; the cell’s powerhouse.

ATP (Adenosine triphosphate)

Universal energy currency of the cell produced mainly by mitochondria during respiration.

Plastid

Double-membraned plant cell organelle; includes chloroplasts, chromoplasts, and leucoplasts.

Chloroplast

Green plastid containing chlorophyll; site of photosynthesis in plant cells.

Chromoplast

Coloured plastid containing pigments like carotenoids; imparts yellow, orange, or red hues to plant parts.

Leucoplast

Colourless plastid that stores starch, oils, or proteins in plant cells.

Vacuole

Membrane-bound sac for storage; large central vacuole in plant cells maintains turgidity and stores cell sap.

Mitosis

Type of cell division producing two genetically identical daughter cells; crucial for growth and tissue repair.

Meiosis

Cell division producing four daughter cells with half the chromosome number; forms gametes for reproduction.

Ribosome

Non-membranous particle of RNA and protein; site where amino acids are assembled into proteins.

Protoplasm

Living substance of a cell, comprising the cytoplasm and the nucleus.

Cell sap

Fluid inside plant vacuoles containing water, ions, sugars, and other dissolved substances that help maintain turgor.

Electron microscope

High-resolution instrument using electron beams to visualize ultrastructural details such as membranes and organelles.