Cell: The Building Block of Life

Comprehensive vocabulary flashcards covering cell structure, organelles, microscopy, and cell division based on the lecture material.

Thermophiles

Heat-loving unicellular bacteria, such as those found in the hot springs of Puga Valley, Ladakh, that thrive in temperatures nearly at the boiling point of water.

Calcium Carbonate Deposits

Substances found by scientists from the Birbal Sahni Institute of Palaeosciences that formed around hot springs and may have protected early organic molecules from harmful radiation.

Cell

The basic level at which life exists and the fundamental structural and functional unit of all living organisms.

Unicellular

Organisms consisting of only one cell, such as bacteria or yeast.

Multicellular

Organisms made up of millions of cells that work together, such as plants, fish, birds, or humans.

Tissues

A group of similar cells performing similar functions.

Organ

A structure formed by different tissues organized together to perform specific functions.

Organ Systems

A group of several organs working together, such as the respiratory system consisting of nasal pores, nasal cavity, trachea, and lungs.

Limit of Resolution of the Human Eye

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

Robert Hooke

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

Light Microscope

An instrument used in school laboratories to observe objects using visible light and objective lenses like $10X$ and $40X$.

Unit Conversion: Millimetre to Micrometre

1\,\text{millimetre (mm)} = 1000\,\text{micrometre (\mu m)}.

Estimated Size of a Cell Formula

$\frac{\text{Diameter of the visible field in micrometre}}{\text{Number of cells along the diameter}}$.

Electron Microscope

A powerful instrument that uses a beam of electrons instead of light to reveal fine details of cell structure at the nanometre scale.

Nanometre (nm)

A unit of length equal to one-billionth of a metre, or $0.000001\,\text{mm}$.

Resolution

A measure of clarity in a microscope image.

Contrast

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

Cell Membrane (Plasma Membrane)

A thin, selectively permeable boundary about $7$ to $10\,\text{nanometres (nm)}$ thick made of lipids and proteins that protects the cell contents.

Selectively Permeable

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

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 concentration to a lower concentration, occurring 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.

Hypertonic Solution

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

Fluid-Mosaic Model

A model of the cell membrane structure featuring a lipid bilayer where molecules can move sideways, flip, and rotate like tiles in a mosaic.

Cell Wall

An additional, rigid, and permeable layer outside the cell membrane found in plants, fungi, and bacteria.

Cellulose

A type of carbohydrate formed by many glucose units that primarily makes up the plant cell wall.

Cytoplasm

A semi-fluid, jelly-like substance inside the cell containing organelles and other substances.

Organelles

Sub-cellular components within the cytoplasm, such as the nucleus and mitochondria, that perform specific jobs.

Prokaryotic Cells

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

Eukaryotic Cells

Cells with a well-defined nucleus and several membrane-bound organelles; examples include plant and animal cells.

Nucleoid

The region in a prokaryotic cell containing genetic material as a single circular DNA molecule.

Cytoskeleton

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

Acellular Agents

Infectious agents like viruses, viroids, and prions that are not composed of cells.

Nucleus

The 'house of coded instructions' containing a nuclear membrane, nucleolus, and genetic information.

Chromosomes

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

Genes

The functional segments of DNA molecules.

Chromatin

An entangled mass of thread-like structures in a non-dividing cell composed of DNA and proteins.

Ribosomes

Tiny structures that are the sites of protein synthesis, found freely in the cytoplasm or attached to the ER.

Rough Endoplasmic Reticulum (RER)

Part of the manufacturing factory that looks rough due to attached ribosomes and is involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

Part of the manufacturing factory without ribosomes, involved in the synthesis and storage of fats and hormones.

Golgi Apparatus

Stacks of flattened, sac-like structures that modify, sort, and package proteins and lipids into vesicles; first observed by Camillo Golgi in 1898.

Lysosomes

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

Mitochondria

Known as the 'powerhouse of the cell,' they release energy via cellular respiration in the form of ATP.

Adenosine Triphosphate (ATP)

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

Plastids

Plant organelles used for food synthesis and storage, including chloroplasts, chromoplasts, and leucoplasts.

Chloroplasts

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

Chromoplasts

Pigmented plastids (yellow, orange, or red) that give 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 for storage and support; in mature plant cells, a large central vacuole is filled with cell sap.

Cell Division

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

Mitosis

The most common type of cell division producing two genetically identical daughter cells from one parent cell.

Meiosis

A two-step cell division process that produces four gametes with half the number of chromosomes for sexual reproduction.

Cell Culture

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

Cell Theory

The principle formulated by Schleiden, Schwann, and Virchow stating all 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.

Programmed Cell Death (PCD)

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

Totipotency

The special ability proposed by Gottlieb Haberlandt for a living plant cell to develop into a complete plant under suitable conditions.