Ch- 5: The fundamental unit of life - Practice Flashcards

Comprehensive vocabulary flashcards covering the discovery of cells, organelles, cell transport, cell division, and cell types based on Std. IX Science notes.

Robert Hooke

The scientist who discovered cells in 1665 while examining a piece of cork (bark of a tree) under a microscope he had developed.

Cell

The basic structural and functional unit of life, as living organisms are made of cells and each cell performs metabolic activities.

Unicellular organism

An organism whose body is composed of only one cell, which carries out all life processes, such as Amoeba, paramaecium, or bacteria.

Multicellular organism

An organism composed of numerous cells, including all plants and animals.

Cell membrane (Plasma membrane)

A living, flexible membrane made of phospholipids that provides shape, protection, and regulates the movement of materials into and out of the cell.

Selectively Permeable Membrane

A property of the cell membrane that allows it to let only specific materials pass in and out of the cell.

Cytoplasm

The fluid filling the cell containing proteins, ions, and organelles; it is the site for most biochemical reactions.

Nucleus

The 'boss of the cell' that controls all cell activities and the inheritance of characters from one generation to another.

Nucleolus

A small spherical body at the center of the nucleus that is responsible for making Ribosomes.

Chromosomes

Rod-like structures formed from condensed chromatin just before cell division, made of DNA and proteins.

DNA

Deoxy ribonucleic acid; the material that makes up chromosomes along with proteins.

Genes

The functional units of chromosomes.

Cell wall

A non-living, completely permeable, rigid structure made of cellulose found in plants, fungi, and bacteria.

Membrane biogenesis

The process of manufacturing cell membranes using proteins and lipids produced by the ER.

Rough Endoplasmic Reticulum (RER)

A network of membranous sheets with ribosomes on the surface that helps in making proteins.

Smooth Endoplasmic Reticulum (SER)

A network of tubules without ribosomes that helps in making lipids and detoxifying poisons and drugs in liver cells.

Golgi apparatus

A series of flattened sacs (cisternae) involved in the storage, modification, and packaging of substances and the formation of lysosomes.

Lysosomes

Single membrane vesicles known as 'suicide bags' because they contain enzymes that digest the cell if metabolism is disturbed.

Mitochondria

The 'powerhouse of the cell' that releases energy in the form of ATP; they possess their own DNA and Ribosomes.

ATP

Adenosine Triphosphate; the molecule used by the body as energy for life processes.

Chloroplast

A green plastid containing chlorophyll that serves as the site of photosynthesis.

Leucoplast

A colourless plastid used for storing starch, oil, and protein granules.

Chromoplast

Coloured plastids that impart colours to flowers, leaves, and fruits.

Vacuole

A fluid-filled sac surrounded by a tonoplast membrane; it provides turgidity and rigidity in plant cells.

Diffusion

The spontaneous movement of a substance from a region of higher concentration to a region of lower concentration.

Osmosis

The movement of water from a region of higher water concentration to lower water concentration through a semi-permeable membrane.

Hypotonic solution

A surrounding medium with a higher water concentration than the cell, causing the cell to swell.

Hypertonic solution

A surrounding medium with a lower water concentration than the cell, causing the cell to shrink.

Isotonic solution

A surrounding medium with the same water concentration as the cell, resulting in no net movement of water.

Mitosis

Cell division in somatic cells resulting in two genetically similar daughter cells with the same number of chromosomes for growth and repair.

Meiosis

Cell division in reproductive organs resulting in four daughter cells with half the number of chromosomes for gamete formation.

Cancer

A disease caused by uncontrolled cell division due to DNA mutations.

Benign tumor

Lumps of cells that stay in one place and do not invade surrounding tissue.

Malignant tumor

A cancerous mass that invades surrounding tissue and spreads to other parts of the body.

Prokaryotic Cell

A cell (specifically $1-10\,\mu m$) lacking a nuclear membrane, characterized by a poorly defined nucleoid and the absence of membrane-bound organelles.

Eukaryotic Cell

A cell (specifically $5-100\,\mu m$) with a well-defined nuclear membrane and membrane-bound organelles like mitochondria and plastids.

Endocytosis

The process by which Amoeba uses its flexible cell membrane and pseudopodia to engulf food particles.