Cell: The Building Block of Life

Flashcards covering the discovery, structure, transport mechanisms, organelles, and division processes of the cell based on the lecture transcript.

Thermophiles

Heat-loving bacteria found in environments like hot springs that maintain very high temperatures.

Birbal Sahni Institute of Palaeosciences

A research institute in Lucknow that studied hot springs in Puga Valley and found rapid calcium carbonate formation.

Cell

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

Tissues

A group of similar cells performing similar functions.

Limit of resolution

The ability of the human eye to see two very close objects as separate and distinct, which is approximately $0.1\,\text{mm}$.

Robert Hooke

The first person to observe a cell in $1665$ using a self-designed microscope, naming the box-like compartments found in cork slices.

Micrometre $(\mu\text{m})$

A unit of measurement used in cell biology where $1\,\text{mm} = 1000\,\mu\text{m}$.

Nanometre (nm)

A unit of measurement equivalent to one-billionth of a metre.

Contrast

In microscopy, the difference in brightness between various parts of an object.

Cell membrane

A thin, selectively permeable boundary that surrounds a cell, protects its contents, and defines its individuality.

Selectively permeable

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

Osmosis

The diffusion of water across a selectively permeable membrane from an area with more water and less solute to an area with less water and more solute.

Diffusion

The net movement of particles from a higher concentration to a lower concentration, occurring due to a concentration gradient.

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, causing cells to swell.

Hypertonic solution

A solution where the solute concentration of the extracellular medium is greater than the solute concentration of the intracellular medium, causing cells to shrink.

Fluid-mosaic model

A model describing the cell membrane as a lipid bilayer where molecules can move sideways, with proteins acting like gatekeepers.

Cell wall

An additional, permeable, and rigid covering outside the cell membrane found in plants, fungi, and bacteria for protection and support.

Cellulose

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

Cytoplasm

A semi-fluid, jelly-like substance in a cell that contains organelles.

Prokaryotic cells

Cells, such as bacterial cells, that lack a well-defined nucleus and membrane-bound organelles.

Eukaryotic cells

Complex cells, such as plant and animal cells, that have a well-defined nucleus and several membrane-bound organelles.

Nucleoid

The region in a prokaryotic cell where DNA is present as a single circular molecule without a surrounding membrane.

Cytoskeleton

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

Cell inclusions

Substances stored in the cytoplasm, such as starch in plants or crystals of calcium oxalate or silica.

Viruses

Acellular infectious agents composed of genetic material with a protein coat.

Nuclear membrane

A double-layered covering of the nucleus containing pores for the transfer of material with the cytoplasm.

Nucleolus

A dense round body within the nucleus responsible for the synthesis of ribosomal subunits.

DNA (Deoxyribonucleic acid)

Molecules containing the genetic information and instructions for inheritance of characters.

Genes

The functional segments of DNA.

Chromatin

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

Chromosomes

Rod-shaped structures visible when a cell is about to divide, composed of organised chromatin.

Ribosomes

Tiny structures, either free or attached to the endoplasmic reticulum, that serve as the sites of protein synthesis.

Rough Endoplasmic Reticulum (RER)

A network with attached ribosomes involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

A network 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.

Camillo Golgi

An Italian scientist who first observed the Golgi apparatus in $1898$ using special staining techniques in barn owl nerve cells.

Lysosomes

Single membrane-bound sacs filled with enzymes that break down unwanted proteins, fats, and cellular waste.

Mitochondria

The 'powerhouses of the cell' where glucose is broken down to release energy during cellular respiration.

Adenosine Triphosphate (ATP)

The molecule stored in mitochondria that acts as the energy currency for cellular activities.

Cristae

Finger-like projections on the inner membrane of mitochondria that increase surface area for chemical reactions.

Chloroplasts

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

Chromoplasts

Plastids containing yellow, orange, or red pigments that provide bright colors to flowers and fruits.

Leucoplasts

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

Central Vacuole

A large organelle in mature plant cells filled with cell sap that maintains cell firmness.

Cell division

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

Mitosis

A common type of cell division producing two genetically identical daughter cells from one parent cell, used for growth and repair.

Meiosis

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

Cell culture

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

Arun Kumar Sharma

A famous Indian scientist known for his work on chromosomes, plant taxonomy, and evolution.

Cell Theory

The principle formulated by Schleiden, Schwann, and Virchow stating all organisms are made of cells and cells arise from pre-existing cells.

Contact inhibition

A process where cell division usually stops when cells come into contact with neighbouring cells.

Programmed Cell Death (PCD)

A genetically regulated process of selective cell destruction essential for normal development, such as finger formation in an embryo.

Totipotency

The special ability of a plant cell to develop into a complete plant if provided with suitable conditions, proposed by Gottlieb Haberlandt.