The Fundamental Unit of Life

Vocabulary practice flashcards covering basic cell terminology, historical discoveries, organelles, transport mechanisms, and modes of cell division from Class 9 biology notes.

Cell

The structural, functional, and biological unit of all living beings that can replicate itself independently and serves as the building block of life.

Robert Hooke

The scientist who first discovered and named the cell in 1665.

Anton Van Leuwenhoek

The scientist who discovered living cells, including protozoa and bacteria, in 1674.

Robert Brown

The scientist who discovered the cell nucleus in 1831.

Schleiden and Schwann

The scientists who proposed the cell theory in 1838 and 1839.

Purkinje

The scientist who coined the term protoplasm in 1839.

Cell Theory

The biological theory stating that all living organisms are composed of cells, and that new cells arise from pre-existing cells through cell division.

Unicellular Organism

An organism made up of a single cell, such as bacteria or Paramecium.

Multicellular Organism

An organism made up of more than one cell, such as humans and animals.

Mycoplasma

The smallest cell, also known as PPLO (Pleuro-Pneumonia like Organisms).

Plasma Membrane

The selectively permeable outermost covering of the cell made of lipids and proteins that regulates the entry and exit of substances.

Passive Transport

The slow movement of small molecules or water from higher to lower concentration without requiring energy.

Active Transport

The rapid movement of large molecules from lower to higher concentration requiring energy in the form of ATP molecules.

Osmosis

The passage of water molecules across a semi-permeable membrane from a higher water concentration to a lower water concentration.

Endosmosis

The process where water molecules or solvent enter into the cell, causing the cell to swell.

Exosmosis

The process where water molecules or solvent move out of the cell, causing the cell to shrink.

Diffusion

The natural process of particle movement from a region of higher concentration to lower concentration in liquids and gases until uniformly spread.

Hypotonic Solution

A solution with higher water and lower solute concentration outside the cell, causing water to move in and the cell to swell.

Hypertonic Solution

A solution with higher solute and lower water concentration outside the cell, causing water to move out and the cell to shrink.

Isotonic Solution

A solution with equal water and solute concentration inside and outside the cell, resulting in no net movement of water.

Cell Wall

A non-living, rigid outer covering lying outside the plasma membrane present in plant, fungi, and bacterial cells.

Plasmolysis

The shrinkage of cell contents away from the cell wall in living plant cells due to water loss through osmosis.

Nucleus

A double-layered membrane-bound organelle containing nuclear pores and chromosomes made of DNA and protein.

Deoxyribose Nucleic Acid (DNA)

Molecules that contain the essential information for constructing and organizing cells, organized into functional segments called genes.

Chromatin Material

An entangled mass of thread-like structures visible in non-dividing cells that organizes into chromosomes during cell division.

Prokaryotic Cell

A small cell ranging from $1 - 10\,\mu m$ ($1\,\mu m = 10^{-6}\,m$) with an undefined nuclear region called a nucleoid, a single chromosome, and no membrane-bound organelles.

Nucleoid

The undefined, non-membrane-enclosed nuclear region present in prokaryotic cells.

Eukaryotic Cell

A cell ranging from $5 - 10\,\mu m$ with a well-defined nucleus surrounded by a nuclear membrane, multiple chromosomes, and membrane-bound organelles.

Endoplasmic Reticulum (ER)

An extensive network of membrane-bound tubes and sheets within eukaryotic cells.

Rough Endoplasmic Reticulum (RER)

A type of endoplasmic reticulum studded with ribosomes that serves as the site for protein synthesis.

Smooth Endoplasmic Reticulum (SER)

A type of endoplasmic reticulum responsible for lipid, hormone, and enzyme production, as well as detoxification in liver cells.

Golgi Apparatus

A system of membrane-bound vesicles arranged in stacks called cisterns that functions in protein packaging, storage, modification, and lysosome formation; known as the 'Traffic police' of the cell.

Camillo Golgi

The scientist who discovered the Golgi apparatus.

Lysosomes

Membrane-bound waste disposal sacs filled with digestive enzymes from the RER, capable of self-digestion and termed 'Suicide bags' of the cell.

Mitochondria

Known as the 'Powerhouse' of the cell, double-membrane bound organelles with inner folds called cristae that generate ATP and contain their own DNA and ribosomes.

ATP

Adenosine triphosphate, the primary energy currency of the cell produced by mitochondria for cellular activities.

Plastids

Double-membrane bound organelles present only in plant cells, existing as colored chromoplasts or colorless leucoplasts.

Chloroplasts

Chlorophyll-containing chromoplasts in plant cells responsible for conducting photosynthesis.

Leucoplasts

Colorless plant plastids that store starch, oils, and protein granules.

Ribosomes

Membrane-less organelles found in both prokaryotic and eukaryotic cells that serve as the primary sites of protein synthesis.

Vacuoles

Storage sacs for liquid or solid contents, occupying $50 - 90\%$ of plant cell volume to provide turgidity and rigidity.

Mitosis

An equational cell division process forming two daughter cells with identical chromosome counts as the parent cell, used for growth and tissue repair.

Meiosis

A reductional cell division process forming four daughter cells with half the number of chromosomes of the parent cell, responsible for producing gametes.