Cell: The Building Block of Life

Comprehensive practice vocabulary flashcards covering the structural components, organelles, cellular transport, cell division, and historical discoveries from Chapter 2: Cell: The Building Block of Life.

Thermophiles

Heat-loving, unicellular bacteria that survive 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 see two close objects as separate and distinct, which is about $0.1\,\text{mm}$ when viewed from a near point of about $25\,\text{cm}$.

Robert Hooke

The scientist who first observed cells in 1665 by examining a thin slice of cork under a self-designed microscope capable of about 200–300X magnification, naming the compartments 'cells'.

Electron Microscope

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

Selectively Permeable Membrane

A biological membrane, such as the plasma membrane, that permits the entry and exit of specific substances while blocking others.

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration, occurring along a concentration gradient even without a membrane.

Osmosis

The net diffusion of water across a selectively permeable membrane from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution).

Isotonic Solution

A solution in which the solute concentration of the extracellular medium is equal to the solute concentration of the intracellular medium, resulting in no net change in cell volume.

Hypotonic Solution

A solution where the solute concentration of the extracellular medium is lower than that of the intracellular medium, causing water to enter the cell and make it swell.

Hypertonic Solution

A solution where the solute concentration of the extracellular medium is higher than that of the intracellular medium, causing water to exit the cell and make it shrink.

Fluid-Mosaic Model

The structural model describing the cell membrane as a $7\text{ to }10\,\text{nm}$ thick lipid bilayer with embedded proteins arranged like tiles in a mosaic, where molecules can rotate, flip, and move sideways.

Cell Wall

A rigid, permeable layer situated outside the cell membrane in plants, fungi, and bacteria that provides shape, structural rigidity, and protection against environmental stresses.

Cellulose

A complex carbohydrate composed of linked glucose units that forms the primary constituent of plant cell walls and serves as dietary roughage in humans.

Prokaryotic Cells

Cells, typically $1\text{ to }10\,\mu\text{m}$ in diameter, that lack a membrane-bound nucleus and membrane-bound organelles, where cellular activities occur directly in the cytoplasm.

Eukaryotic Cells

Complex cells, typically $10\text{ to }100\,\mu\text{m}$ in diameter, containing a distinct membrane-bound nucleus and specialized membrane-bound organelles.

Cytoskeleton

A network of fine fibres in eukaryotic cells, visible only under an electron microscope, that provides structural support, maintains cell shape, and facilitates cell movement and internal transport.

Cell Inclusions

Non-living components stored in the cytoplasm, including starch in plant cells and crystals of calcium oxalate or silica.

Viroids

Acellular infectious agents that consist of genetic material lacking a surrounding protein coat.

Prions

Acellular infectious agents comprised of misfolded proteins that entirely lack genetic material.

Nucleolus

A dense, round body inside the nucleus where ribosomal subunits are synthesized before exiting to the cytoplasm.

Chromatin Material

An entangled mass of thread-like material composed of DNA and proteins in a non-dividing nucleus that organizes into distinct chromosomes during cell division.

Chromosomes

Rod-shaped structures visible during cell division composed of DNA and proteins that carry inherited genetic information from parents to the next generation.

Genes

The functional segments of DNA molecules that carry specific instructions for inherited traits.

Nucleoid

The poorly defined, unmembrane-bound region in a prokaryotic cell that contains genetic material in the form of a single circular DNA molecule.

Enucleate Cells

Cells lacking a nucleus, such as mature human Red Blood Cells (RBCs), which lack a nucleus to allow more space for haemoglobin to transport oxygen and survive for approximately $120\,\text{days}$.

Ribosomes

Tiny structures found free in the cytoplasm or bound to the endoplasmic reticulum that serve as the protein factories of the cell.

Rough Endoplasmic Reticulum (RER)

A membranous network continuous with the nuclear envelope, studded with ribosomes on its surface, and actively involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

A membranous network lacking ribosomes on its surface, responsible for the synthesis and storage of lipids (fats) and hormones.

Golgi Apparatus

An organelle consisting of stacks of flattened membrane sacs that modifies, sorts, and packages proteins and lipids into vesicles for transport, secretion, or lysosome formation.

Camillo Golgi

The Italian scientist who first discovered the thread-like network of the Golgi apparatus in 1898 in the nerve cells of a barn owl using specialized staining techniques.

Lysosomes

Single membrane-bound sacs containing digestive enzymes that break down unwanted carbohydrates, fats, proteins, and worn-out organelles to clean the cell.

Mitochondria

Double-membrane-bound organelles known as the powerhouses of the cell where cellular respiration occurs to release energy stored as ATP.

Cristae

Finger-like folds of the inner mitochondrial membrane that expand the surface area available for chemical reactions producing ATP.

Adenosine Triphosphate (ATP)

The energy currency molecule of the cell, generated during cellular respiration in mitochondria to power cellular activities.

Chloroplasts

Double-membrane-bound plant plastids containing chlorophyll, stroma, and disc-shaped membrane structures that absorb sunlight to carry out photosynthesis.

Stroma

The semi-fluid substance within the chloroplast surrounding disc-shaped membranes, where synthesized sugars and starch granules are stored.

Chromoplasts

Plastids containing yellow, orange, or red pigments that impart vibrant colours to flower petals and fruits to attract pollinators and aid seed dispersal.

Leucoplasts

Colourless plastids found in plant storage tissues (such as potato and taro) that function in storing starch, oils, or proteins.

Vacuole

A membrane-bound storage organelle prominent in mature plant cells that stores cell sap, maintaining pressure to keep the plant cell firm.

Cell Sap

The watery fluid contained within a plant vacuole, composed of water, minerals, sugars, and cellular waste products.

J. Craig Venter

The scientist whose team in 2010 chemically synthesized the complete DNA of Mycoplasma mycoides and inserted it into a recipient cell, demonstrating that DNA directs cellular functions.

Mitosis

A mode of cell division that produces two genetically identical daughter cells with the same chromosome number as the parent cell, essential for growth and repair.

Meiosis

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

Cell Culture

A laboratory method of growing and multiplying cells outside an organism's body within a nutrient-rich medium under sterile, controlled conditions.

Arun Kumar Sharma

An Indian botanist recognized for his work on chromosomes, plant taxonomy, and evolution, who received the Shanti Swarup Bhatnagar award and Padma Bhushan.

Cell Theory

The biological principle formulated through the work of Matthias Schleiden, Theodor Schwann, and Rudolf Virchow stating that all living things consist of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Rudolf Virchow

The German scientist who expanded Cell Theory in 1855 by establishing that all new cells arise strictly from pre-existing cells.

Contact Inhibition

A growth control process in normal animal cells where cell division halts upon contact with neighbouring cells, a regulatory mechanism lost in cancer cells.

Programmed Cell Death (PCD)

A genetically regulated process of selective cell destruction essential for normal development, cellular quality control, and shaping structures such as embryonic digits.

Totipotency

The ability of a single living plant cell to develop into a complete plant under suitable nutrient and environmental conditions, proposed by Gottlieb Haberlandt in 1902.