Cell: The Building Block of Life

Vocabulary flashcards covering cell structure, organelles, microscopy, types of cell division, and foundational biological principles based on the lecture notes.

Thermophiles

Heat-loving bacteria that are unicellular and found in environments like the hot springs of Puga Valley in Ladakh.

Cell

The basic level at which life exists and the fundamental unit of structure and function in all living organisms.

Unicellular

Organisms that consist 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.

Tissue

A group of similar cells performing similar functions.

Limit of resolution of the human eye

The ability to see two very close objects as separate and distinct, which is approximately $0.1\,mm$ when viewed from about $25\,cm$.

Robert Hooke

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

Electron microscope

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

Resolution

A measure of clarity in an image produced by a microscope.

Contrast

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

Cell membrane (Plasma membrane)

A thin, selectively permeable boundary made of lipids and proteins that surrounds a cell and protects its 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).

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 explaining the cell membrane structure as a lipid bilayer with proteins embedded in it, where molecules can move sideways, flip, and rotate.

Cell wall

An additional rigid, permeable layer outside the cell membrane found in plants, fungi, and bacteria; in plants, it is primarily made of cellulose.

Cellulose

A type of carbohydrate formed by many glucose units linked together that makes up the plant cell wall and acts as roughage in the human diet.

Prokaryotic cells

Cells that lack a well-defined nucleus and membrane-bound organelles, typically ranging from $1$ to $10\,\mu m$ in diameter.

Eukaryotic cells

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

Cytoplasm

A semi-fluid, jelly-like substance inside the cell that contains organelles and other sub-cellular components.

Organelles

Sub-cellular components within the cytoplasm that perform specific jobs, such as building materials, removing waste, or providing energy.

Nucleus

A double-membraned organelle containing genetic information and the nucleolus; often referred to as the house of coded instructions.

Nucleolus

A dense round body in the nucleus where the synthesis of ribosomal subunits takes place.

Chromosomes

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

Genes

The functional segments of Deoxyribonucleic acid (DNA).

Nucleoid

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

Ribosomes

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

Endoplasmic Reticulum (ER)

A large network organelle involved in the synthesis and transport of proteins, lipids, and hormones.

Rough Endoplasmic Reticulum (RER)

A type of ER with ribosomes attached to its surface, mainly involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

A type of ER without ribosomes on its surface, involved in the synthesis and storage of fats and hormones.

Golgi apparatus

A stack of flattened, sac-like structures that modifies, sorts, and packages proteins and lipids into vesicles for transport.

Lysosomes

Single membrane-bound sacs filled with enzymes that break down waste materials and damaged parts of the cell.

Mitochondria

The 'powerhouses of the cell' that supply energy by breaking down glucose during cellular respiration to produce ATP.

Adenosine Triphosphate (ATP)

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

Plastids

Special organelles in plant cells used for food synthesis and storage, including chloroplasts, chromoplasts, and leucoplasts.

Chloroplasts

Double-membrane-bound plastids containing chlorophyll where photosynthesis occurs.

Chromoplasts

Pigmented plastids (yellow, orange, or red) that provide bright colors to flowers and fruits to attract pollinators.

Leucoplasts

Colourless plastids that store food materials such as starch, oils, or proteins.

Vacuoles

Storage organelles filled with cell sap that store water, minerals, and waste; plant cells typically have one large central vacuole.

Cell division

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

Mitosis

A type of cell division that produces two genetically identical daughter cells for growth, repair, and asexual reproduction.

Meiosis

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

Cell culture

A method to grow plant and animal cells outside the body in a nutrient-rich medium under sterile conditions.

Cell Theory

The principle stating that 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 animal cells where cell division stops when cells come into contact with neighboring cells.

Programmed Cell Death (PCD)

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

Totipotency

The ability of a living plant cell to develop into a complete plant if provided with suitable conditions.