The Fundamental Unit of Life – Key Vocabulary

Vocabulary flashcards summarising the main terms and definitions from the lecture notes on “The Fundamental Unit of Life,” covering cell discovery, structures, functions, and key biological processes.

Cell

The fundamental structural and functional unit of life; discovered by Robert Hooke in 1665.

Robert Hooke

Scientist who first observed and named ‘cells’ while examining cork in 1665.

Unicellular Organism

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

Multicellular Organism

An organism composed of many cells that perform specialized functions, e.g., plants, animals.

Cell Theory

Concept stating that all plants and animals are composed of cells and that cells arise from pre-existing cells.

Prokaryote

Organism whose cells lack a true nucleus and membrane-bound organelles; possesses a nucleoid region.

Eukaryote

Organism with cells that contain a membrane-bound nucleus and various membrane-bound organelles.

Plasma Membrane (Cell Membrane)

Outer covering of the cell; selectively permeable lipid-protein layer controlling substance entry and exit.

Selectively Permeable Membrane

A barrier that allows some substances to pass while restricting others; property of the plasma membrane.

Diffusion

Spontaneous movement of molecules from high to low concentration, e.g., O₂ and CO₂ exchange across membranes.

Osmosis

Net diffusion of water across a selectively permeable membrane toward a higher solute concentration.

Hypotonic Solution

Medium with higher water (lower solute) concentration than the cell; causes cells to swell as water enters.

Isotonic Solution

Medium with equal water concentration to the cell; results in no net water movement and no size change.

Hypertonic Solution

Medium with lower water (higher solute) concentration than the cell; causes cells to shrink as water leaves.

Endocytosis

Process by which a cell engulfs external material via membrane infolding; used by Amoeba for feeding.

Cell Wall

Rigid outer layer in plant, fungal and bacterial cells composed mainly of cellulose; provides structural strength.

Plasmolysis

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

Nucleus

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

Nuclear Membrane

Double membrane surrounding the nucleus, containing pores for material exchange with cytoplasm.

Chromosome

Rod-shaped structure of DNA and protein visible during cell division; carries hereditary information.

DNA (Deoxyribonucleic Acid)

Molecule storing genetic information for constructing and organizing cells.

Gene

Functional segment of DNA that controls specific traits and cellular functions.

Nucleoid

Poorly defined nuclear region in prokaryotes lacking a nuclear membrane.

Protoplasm

Fluid living substance of the cell, including cytoplasm and nucleus; term coined by Purkinje.

Cytoplasm

Fluid content within the plasma membrane outside the nucleus; contains organelles and performs metabolic activities.

Cell Organelle

Membrane-bound intracellular structure performing specialized functions, e.g., mitochondria, ER, Golgi.

Endoplasmic Reticulum (ER)

Network of membrane-bound tubules and sacs; pathways for transport and site of biomolecule synthesis.

Rough Endoplasmic Reticulum (RER)

ER region studded with ribosomes; synthesizes and transports proteins.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes; synthesizes lipids and detoxifies poisons and drugs.

Membrane Biogenesis

Formation of new cell membrane using proteins and lipids produced by ER.

Golgi Apparatus

Stack of membrane-bound cisterns that modify, sort, store and package cellular products; forms lysosomes.

Lysosome

Membrane sac of digestive enzymes that breaks down waste and foreign material; called ‘suicide bag’ when ruptured.

Mitochondrion

Double-membraned ‘powerhouse’ organelle generating ATP; contains its own DNA and ribosomes.

ATP (Adenosine Triphosphate)

Energy currency molecule synthesized mainly in mitochondria; fuels cellular work.

Plastid

Plant-cell organelle of two main types—chromoplasts (coloured) and leucoplasts (storage).

Chloroplast

Green chromoplast containing chlorophyll; site of photosynthesis; possesses its own DNA and ribosomes.

Chromoplast

Pigmented plastid (other than green), contributing yellow, orange or red colours to plant parts.

Leucoplast

Colourless plastid specialized for storage of starch, oils or proteins.

Vacuole

Membrane-bound sac for storage; large and central in plant cells, small in animal cells.

Ribosome

Non-membrane-bound particle composed of RNA and protein; site of protein synthesis.

Mitosis

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

Meiosis

Cell division producing four daughter cells with half the chromosome number, forming gametes for reproduction.