Cell: The Building Block of Life

A collection of vocabulary flashcards covering the fundamental concepts of cell biology, including cell structure, organelles, membranes, cell division, and cell theory based on the lecture notes.}.

Thermophiles

Mostly heat-loving bacteria that are unicellular and found in extreme environments like the hot springs of Puga Valley.

Birbal Sahni Institute of Palaeosciences

The institute in Lucknow whose scientists studied hot springs in Ladakh and found rapid calcium carbonate formation.

Limit of resolution

The ability of the human eye to see two very close objects as separate and distinct, which 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 while examining a thin slice of cork.

Micrometre ($\mu m$)

A unit of measurement used for cell size, where $1\,millimetre\,(mm) = 1000\,micrometre\,(\mu m)$.

Nanometre ($nm$)

A unit of measurement equal to one-billionth of a metre, used to see cell structures via electron microscopes.

Cell membrane

A thin, selectively permeable lipid bilayer with embedded proteins that surrounds a cell and protects its contents; also called the plasma membrane.

Osmosis

The movement of water through 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 to a lower concentration, which occurs even without a membrane.

Hypotonic solution

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

Hypertonic solution

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

Isotonic solution

A solution where the solute concentration of the extracellular medium equals the solute concentration of the intracellular medium.

Fluid-mosaic model

The model explaining cell membrane structure where molecules can move sideways, flip, and rotate within a lipid bilayer embedded with mosaic-like proteins.

Cell wall

An additional rigid, permeable covering outside the cell membrane in plants, fungi, and bacteria that provides structural support and protection.

Cellulose

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

Prokaryotic cells

Cells that lack a well-defined nucleus and membrane-bound organelles; the genetic material is located in a region called the nucleoid.

Eukaryotic cells

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

Cytoskeleton

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

Nucleus

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

Nucleolus

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

DNA (Deoxyribonucleic acid)

Molecules within chromosomes that contain genetic information; functional segments are called genes.

Chromatin

An entangled mass of thread-like structures in a non-dividing cell that organises into chromosomes when the cell is about to divide.

Ribosomes

Tiny structures that serve as the protein factories of the cell, either floating freely in the cytoplasm or attached to the endoplasmic reticulum.

Rough Endoplasmic Reticulum (RER)

An organelle involved in protein synthesis and secretion that appears rough under a microscope due to attached ribosomes.

Smooth Endoplasmic Reticulum (SER)

An organelle involved in the synthesis and storage of fats (lipids) and hormones, lacking ribosomes on its surface.

Golgi apparatus

A stack of flattened, sac-like structures that acts as the cell's post office by modifying, sorting, and packaging proteins and lipids into vesicles.

Lysosomes

Single membrane-bound sacs filled with enzymes that serve as the cell's clean-up system by breaking down waste and damaged organelles.

Mitochondria

Often called the 'powerhouses of the cell,' these organelles break down glucose during cellular respiration to release energy stored as ATP.

Adenosine Triphosphate (ATP)

The molecule that acts as the energy currency for most cellular activities.

Chloroplasts

Double-membrane-bound plastids containing the green pigment chlorophyll, where photosynthesis and sugar synthesis occur.

Chromoplasts

Plastids containing yellow, orange, or red pigments that provide bright colours to flowers and fruits to attract pollinators.

Leucoplasts

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

Vacuoles

Organelles used for storage and support; in mature plant cells, a large central vacuole filled with cell sap maintains cell firmness.

Cell division

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

Mitosis

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

Meiosis

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

Cell Theory

The principle formulated by Schleiden ($1838$), Schwann ($1839$), and Virchow ($1855$) stating all organisms are made of cells, cells are the basic unit of life, and all cells arise from pre-existing cells.

Contact inhibition

A process where animal cell division stops when cells come in contact with neighbouring cells; this control is lost in cancer cells.

Programmed Cell Death (PCD)

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

Totipotency

The ability of a living plant cell to develop into a complete plant if provided with suitable nutrients and conditions, as proposed by Gottlieb Haberlandt in $1902$.