Cell: The Building Block of Life - Vocabulary Flashcards

Comprehensive vocabulary flashcards covering key terms, cell structures, organelles, division processes, and foundational scientific principles from Chapter 2: Cell: The Building Block of Life.

Thermophiles

Heat-loving, unicellular bacteria capable of surviving in extreme, high-temperature environments such as the hot springs of Puga Valley in Ladakh.

Limit of resolution of the human eye

The ability of the human eye to distinguish two close points as separate, which is about $0.1\,\text{mm}$ when viewed from a distance of about $25\,\text{cm}$.

Robert Hooke

The scientist who first observed cork cells in $1665$ as small box-like compartments using a self-designed microscope with about $200\text{--}300\text{X}$ magnification.

Light microscope

An optical instrument that uses visible light and a combination of objective lenses and an eyepiece to produce magnified images of small objects.

Electron microscope

A powerful instrument that uses a beam of electrons instead of light to produce highly magnified images of cell structures at the nanometre scale.

Cell membrane

A thin boundary ($7\text{ to }10\,\text{nm}$ thick) made of lipids and proteins that surrounds a cell, defines its individuality, and selectively regulates the passage of substances.

Osmosis

The net movement of water through a selectively permeable membrane from an area with more water and less solute to an area with less water and more solute.

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

Isotonic solution

A solution in which the solute concentration of the extracellular medium is equal to the solute concentration of the intracellular medium.

Hypotonic solution

A solution in which the solute concentration of the extracellular medium is less than the solute concentration of the intracellular medium.

Hypertonic solution

A solution in which the solute concentration of the extracellular medium is greater than the solute concentration of the intracellular medium.

Fluid-mosaic model

A structural model of the cell membrane consisting of a fluid lipid bilayer with embedded protein molecules arranged like tiles in a mosaic.

Cell wall

A rigid, permeable outer layer surrounding the cell membrane in plant, fungal, and bacterial cells that provides protection, firmness, and structural support.

Cellulose

A carbohydrate composed of linked glucose units that forms the primary structural material of plant cell walls and serves as dietary roughage.

Prokaryotic cells

Cells that lack a well-defined nucleus and membrane-bound organelles, in which most cellular activities occur directly in the cytoplasm.

Eukaryotic cells

Cells containing a well-defined nucleus enclosed by a membrane alongside several membrane-bound organelles.

Cytoskeleton

A network of fine fibres in eukaryotic cells that provides structural support, maintains cell shape, and enables movement and internal transport.

Cell inclusions

Stored non-living materials within the cytoplasm, such as starch granules or crystals of calcium oxalate and silica in plant cells.

Acellular infectious agents

Non-cellular entities—including viruses, viroids, and prions—that are too small to be seen under a light microscope.

Nucleus

A double-membrane bound organelle containing genetic material (chromosomes/DNA) that acts as the house of coded instructions for cellular activities.

Nucleolus

A dense, round body inside the nucleus where the synthesis of ribosomal subunits takes place.

Chromosomes

Rod-shaped structures composed of DNA and proteins visible during cell division that carry hereditary information from parents to offspring.

Genes

Functional segments of DNA molecules that store genetic information for inheritance and protein synthesis.

Chromatin material

An entangled mass of thread-like DNA and protein structures present inside the nucleus of a non-dividing eukaryotic cell.

Nucleoid

The region in a prokaryotic cell that contains its single circular DNA molecule without a surrounding nuclear membrane.

Ribosomes

Tiny non-membrane bound cellular structures, either free in the cytoplasm or attached to the endoplasmic reticulum, that serve as sites of protein synthesis.

Rough Endoplasmic Reticulum (RER)

A membrane network studded with ribosomes on its surface, primarily involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

A membrane network lacking ribosomes on its surface, involved in the synthesis and storage of fats (lipids) and hormones.

Golgi apparatus

An organelle consisting of stacks of flattened, sac-like structures that modifies, sorts, and packages proteins and lipids into vesicles.

Camillo Golgi

An Italian scientist who first observed the thread-like network of the Golgi apparatus in $1898$ within the nerve cells of a barn owl.

Lysosomes

Single membrane-bound sacs filled with digestive enzymes that function as a cellular clean-up system by breaking down waste and worn-out organelles.

Mitochondria

Double-membrane bound organelles known as the powerhouses of the cell, where cellular respiration releases energy stored as ATP.

Adenosine Triphosphate (ATP)

The primary chemical molecule that serves as energy currency for cellular activities, produced during cellular respiration in mitochondria.

Plastids

Double-membrane bound organelles found in plant cells that function as centers for food synthesis and storage.

Chloroplasts

Double-membrane plant plastids containing chlorophyll that absorb sunlight to synthesize sugars through photosynthesis.

Chromoplasts

Pigmented plant plastids (yellow, orange, or red) that impart bright colours to flowers and fruits to attract pollinators and seed dispersers.

Leucoplasts

Colourless plant plastids specialized for storing food materials such as starch, oils, or proteins.

Vacuole

A central membrane-bound storage organelle filled with watery cell sap that maintains turgor pressure to keep plant cells firm.

Mitosis

A type of cell division that produces two genetically identical daughter cells with the same number of chromosomes as the parent cell.

Meiosis

A two-step cell division process in reproductive organs that yields four daughter cells (gametes), each containing half the chromosome number of the parent cell.

Totipotency

The capacity of a living mature plant cell to develop into a complete plant organism when supplied with appropriate nutrients and environmental conditions.

Cell Theory

The unifying biological principle formulated by Schleiden, Schwann, and Virchow stating that all living beings are composed of cells, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells.

Contact inhibition

A regulatory mechanism in normal animal cells where cell division stops once a cell makes contact with neighbouring cells.

Programmed Cell Death (PCD)

A genetically regulated, organized process of selective cell destruction necessary for normal development, immune function, and quality control.