Cell: The Building Block of Life

Comprehensive vocabulary flashcards covering cell biology, including cell structures, organelles, division processes, and the historical development of cell theory.

Thermophiles

Heat-loving bacteria that are unicellular and thrive in environments like the hot springs of Puga Valley in Ladakh where temperatures are nearly at the boiling point.

Cell

The basic structural and functional unit of life that represents the basic level at which life exists.

Tissues

A group of similar cells performing similar functions.

Limit of resolution

The ability of the human eye to see two very close objects as separate and distinct, which for the human eye is $0.1\,mm$ at a distance of about $25\,cm$.

Robert Hooke

The first person to observe a cell in 1665 using a self-designed microscope to examine a thin slice of cork; he named the box-like compartments 'cells'.

Resolution

A measure of clarity in a microscope image.

Contrast

The difference in brightness between various parts of an object being observed under a microscope.

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 (Plasma membrane)

A thin, selectively permeable boundary that surrounds a cell, protects its contents, and defines its individuality.

Selectively permeable

A property of the cell membrane that allows some substances to pass through it while blocking others.

Osmosis

The diffusion of water across a selectively permeable membrane from an area with more water (dilute solution) to an area with less water (concentrated solution).

Diffusion

The net movement of particles from a higher concentration to a lower concentration, occurring due to a concentration gradient 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 a cell 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 a cell to shrink.

Fluid-mosaic model

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

Cell wall

An additional, rigid, and permeable covering outside the cell membrane found in plants, fungi, and bacteria to provide structural support and protection.

Cellulose

A type of carbohydrate formed by many glucose units linked together that primarily composes the plant cell wall and acts as roughage in the human diet.

Cytoplasm

A semi-fluid, jelly-like substance within the cell that contains several sub-cellular components called organelles.

Prokaryotic cell

A cell that lacks a well-defined nucleus and membrane-bound organelles; examples include bacterial cells.

Eukaryotic cell

A cell containing a well-defined nucleus and several membrane-bound organelles, typically ranging from $10$ to $100\,\mu m$ in diameter.

Nucleoid

The region in a prokaryotic cell that contains the genetic material in the form of a single circular DNA molecule associated with specific proteins.

Cytoskeleton

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

Acellular agents

Infectious agents such as viruses, viroids, and prions that do not consist of cells and are too small to be seen under a light microscope.

Nuclear membrane

A double-layered covering of the nucleus containing pores that allow the transfer of material between the nucleus and the cytoplasm.

Nucleolus

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

Chromosomes

Rod-shaped structures composed of DNA and specific proteins that contain information for inheritance of characters from parents to offspring.

DNA (Deoxyribonucleic acid)

The molecule that contains genetic information; its functional segments are called genes.

Chromatin

An entangled mass of thread-like structures present in the nucleus of a non-dividing cell, which organizes into chromosomes when the cell is about to divide.

Ribosomes

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

Rough Endoplasmic Reticulum (RER)

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

Smooth Endoplasmic Reticulum (SER)

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

Golgi apparatus

A stack of flattened, sac-like structures that modifies, sorts, and packages proteins and lipids into vesicles for transport or secretion.

Lysosomes

Single membrane-bound sacs filled with enzymes that break down unwanted proteins, carbohydrates, fats, and damaged cell parts; known as the cell's clean-up system.

Mitochondria

The 'powerhouse of the cell' where glucose is broken down to release energy in the form of ATP during cellular respiration.

Cristae

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

ATP (Adenosine Triphosphate)

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

Chloroplasts

Double-membrane-bound plastids containing the green pigment chlorophyll used by plants for food synthesis via photosynthesis.

Chromoplasts

Plastids containing yellow, orange, or red pigments that provide bright colors to flowers and fruits to attract pollinators and aid seed dispersal.

Leucoplasts

Colourless plastids that store food materials such as starch, oils, or proteins.

Vacuoles

Storage organelles filled with cell sap; in mature plant cells, a large central vacuole helps maintain pressure and keep the cell firm.

Cell division

The process by which new cells are formed from pre-existing cells, allowing for growth, repair, and reproduction.

Mitosis

A type of cell division that produces two genetically identical daughter cells from one parent cell, essential for growth and repair.

Meiosis

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

Cell culture

The process of taking cells from an organism and growing/multiplying them outside the body in a nutrient-rich medium under sterile conditions.

Cell Theory

The unifying principle of biology stating that 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 in many animal cells where cell division stops when cells come into contact with neighbouring cells; this control is lost in cancer cells.

Programmed Cell Death (PCD)

A genetically regulated and organized process of selective cell destruction essential for normal development and cellular quality control.

Totipotency

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