Cell: The Building Block of Life

A comprehensive vocabulary set covering the discovery, structure, functions, and divisions of the building blocks of life based on lecture notes.

Thermophiles

Heat-loving, unicellular bacteria that live in extreme environments such as the hot springs of Puga Valley in Ladakh.

Cell

The basic structural and functional unit at which life exists in all living organisms.

Tissues

A group of similar cells organized to perform similar functions.

Limit of resolution

The ability of the human eye to see two very close objects as separate and distinct, which is about $0.1\,mm$ when viewed from $25\,cm$.

Robert Hooke

The first person to observe a cell in $1665$ using a self-designed microscope to examine a thin slice of cork.

Micrometre ($\mu m$)

A unit of measurement used for microscopic structures where $1\,mm = 1000\,\mu m$.

Nanometre ($nm$)

A unit of measurement equal to one-billionth of a metre ($10^{-9}\,m$).

Electron microscope

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

Cell membrane

Also called the plasma membrane, this is a thin, selectively permeable boundary made of lipids and proteins that protects cell contents.

Osmosis

The movement of water through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Diffusion

The net movement of particles from a higher concentration to a lower concentration which occurs even without a membrane.

Isotonic solution

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

Hypotonic solution

A solution where the solute concentration of the extracellular medium is less than the solute concentration of the intracellular medium, causing cells to swell.

Hypertonic solution

A solution where the solute concentration of the extracellular medium is greater than the solute concentration of the intracellular medium, causing cells to shrink.

Fluid-mosaic model

A model describing the cell membrane as a lipid bilayer with embedded proteins that can move sideways, flip, and rotate.

Cell wall

A rigid, permeable outer layer found in plants, fungi, and bacteria that helps maintain cell shape and withstand environmental stress.

Cellulose

A type of carbohydrate formed by linked glucose units that primarily composes the plant cell wall.

Cytoplasm

A semi-fluid, jelly-like substance inside the cell containing organelles, where most cellular activities take place in prokaryotes.

Organelles

Membrane-bound sub-cellular components in the cytoplasm that perform specific jobs, like a tiny living factory.

Prokaryotic cells

Primitive cells, such as bacteria, that lack a well-defined nucleus and membrane-bound organelles, typically $1$ to $10\,\mu m$ in diameter.

Eukaryotic cells

Complex cells, such as those in plants and animals, that have a well-defined nucleus and several membrane-bound organelles.

Cytoskeleton

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

Cell inclusions

Substances stored in the cytoplasm such as starch, calcium oxalate crystals, or silica.

Nucleus

The double-layered 'house of coded instructions' that contains chromosomes and genetic information for inheritance.

Nucleolus

A dense round body inside the nucleus where the synthesis of ribosomal subunits occurs.

Chromosomes

Rod-shaped structures composed of DNA and proteins, visible only when a cell is about to divide.

DNA (Deoxyribonucleic acid)

Molecules that contain genetic information and are the functional segments of chromosomes.

Genes

The functional segments of DNA responsible for the inheritance of characters.

Chromatin

An entangled mass of thread-like structures visible in the nucleus of a non-dividing cell.

Nucleoid

The region in a prokaryotic cell containing genetic material as a single circular molecule without a surrounding membrane.

Ribosomes

The 'protein factories' of the cell, which may be free-floating in the cytoplasm or attached to the endoplasmic reticulum.

Endoplasmic Reticulum (ER)

A large network of membranes continuous with the nuclear envelope involved in the synthesis and transport of proteins and lipids.

Rough Endoplasmic Reticulum (RER)

A type of ER with ribosomes attached to its surface, mainly involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

A type of ER without ribosomes on its surface, involved in the synthesis and storage of fats (lipids) and hormones.

Golgi apparatus

The cell's 'post office,' consisting of stacks of flattened sacs that modify, sort, and package proteins and lipids into vesicles.

Lysosomes

The 'clean-up system' of the cell, containing enzymes that break down unwanted proteins, fats, and damaged cell parts.

Mitochondria

The 'powerhouses of the cell' that supply energy in the form of ATP through the process of cellular respiration.

ATP (Adenosine Triphosphate)

The energy currency of the cell used for most cellular activities.

Cristae

Finger-like projections formed by the folding of the inner mitochondrial membrane to increase surface area for chemical reactions.

Plastids

Organelles in plant cells used for food synthesis and storage, categorized into chloroplasts, chromoplasts, and leucoplasts.

Chloroplasts

Double-membrane-bound plastids containing the green pigment chlorophyll used for photosynthesis.

Stroma

The semi-fluid substance inside a chloroplast where sugars and starch granules are stored.

Chromoplasts

Pigmented plastids (yellow, orange, or red) that provide bright colors to flower petals and fruits to attract pollinators.

Leucoplasts

Colorless plastids found in cells like potato or Colocasia that store starch, oils, or proteins.

Vacuoles

Organelles used for storage of water, minerals, and waste; in plant cells, a large central vacuole filled with cell sap maintains pressure.

Mitosis

The most common type of cell division that produces two genetically identical daughter cells from one parent cell, used for growth and repair.

Meiosis

A two-step cell division process occurring in reproductive organs that produces four gametes with half the number of chromosomes.

Cell Theory

The principle stating all living organisms are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Contact inhibition

A process where animal cell division stops upon contact with neighboring cells, a mechanism lost by cancerous cells.

Programmed Cell Death (PCD)

A genetically regulated process of selective cell destruction essential for normal development and immune function.

Totipotency

The ability of a mature plant cell to develop into a complete plant if provided with suitable nutrients and conditions.

Cell culture

The process of growing plant or animal cells outside the body in a nutrient-rich medium under sterile conditions.