Chapter 2: Cell: The Building Block of Life - Vocabulary Flashcards

Comprehensive vocabulary flashcards covering key definitions, cell structures, organelles, division mechanisms, historical discoveries, and cell biology terminology from Chapter 2.

Thermophiles

Heat-loving, mostly unicellular bacteria that survive in extreme environments with very high temperatures, such as the hot springs of Puga Valley in Ladakh.

Limit of Resolution of the Human Eye

The ability of the human eye to see two very close objects as separate and distinct, which is about $0.1\,mm$ when viewed from a distance of about $25\,cm$.

Robert Hooke

The scientist who first observed cells in 1665 using a self-designed microscope with about $200\text{X}$ to $300\text{X}$ magnification while examining a thin slice of cork.

Resolution

A primary feature of microscopy defined as the measure of clarity of an observed image.

Contrast

A feature of microscopy defined as the difference in brightness between various parts of an object.

Electron Microscope

A powerful microscope that uses a beam of electrons instead of light to reveal fine details of cell structures at the nanometre scale ($1\,nm = 0.000001\,mm$).

Cell Membrane (Plasma Membrane)

A thin, selectively permeable outer boundary about $7\text{ to }10\,nm$ thick made of lipids and proteins that surrounds a cell and protects its contents.

Selectively Permeable

A characteristic of a membrane that allows specific 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 (dilute) to an area with less water and more solute (concentrated).

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration due to a concentration gradient, 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 structural model of the cell membrane consisting of a fluid lipid bilayer with embedded proteins arranged like tiles in a mosaic.

Cell Wall

A rigid, permeable outer covering outside the cell membrane found in plant, fungal, and bacterial cells that provides protection, shape, and structural support.

Cellulose

A carbohydrate made of linked glucose units that forms the plant cell wall and acts as roughage in human digestion.

Prokaryotic Cell

A primitive cell lacking a well-defined nucleus and membrane-bound organelles, typically ranging from $1\text{ to }10\,\mu m$ in diameter.

Eukaryotic Cell

A cell containing a well-defined nucleus and membrane-bound organelles, typically ranging from $10\text{ to }100\,\mu m$ in diameter.

Cytoskeleton

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

Cell Inclusions

Stored non-living materials within the cytoplasm, such as starch or crystals of calcium oxalate or silica.

Nucleus

A double-membrane organelle containing genetic information in the form of DNA/chromosomes that controls the structure and activities of a eukaryotic cell.

Nucleolus

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

Chromosomes

Rod-shaped structures composed of DNA and specific proteins, visible during cell division, that carry genetic information for inheritance.

Genes

Functional segments of DNA molecules.

Chromatin

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

Nucleoid

The region in a prokaryotic cell that contains its single circular DNA molecule associated with specific proteins without an enclosing membrane.

Ribosomes

Tiny structures located freely in the cytoplasm or attached to the endoplasmic reticulum that serve as the primary sites of protein synthesis.

Rough Endoplasmic Reticulum (RER)

Endoplasmic reticulum studded with ribosomes on its surface, primarily involved in protein synthesis and secretion.

Smooth Endoplasmic Reticulum (SER)

Endoplasmic reticulum lacking ribosomes on its surface, involved in the synthesis and storage of fats (lipids) and hormones.

Golgi Apparatus

Stacks of flattened, sac-like structures that modify, sort, and package proteins and lipids into vesicles for transport, secretion, or lysosome formation.

Camillo Golgi

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

Lysosomes

Membrane-bound sacs filled with powerful digestive enzymes that break down waste materials and damaged cell parts to keep the cell clean.

Mitochondria

Double-membrane organelles known as the 'powerhouses of the cell' where glucose is broken down during cellular respiration to release ATP.

Cristae

Finger-like folds of the inner mitochondrial membrane that increase the surface area for chemical reactions and energy production.

Adenosine Triphosphate (ATP)

The energy currency molecule of the cell produced and stored in mitochondria during cellular respiration.

Plastids

Special double-membrane organelles present in plant cells used for food synthesis and storage.

Chloroplasts

Double-membrane plastids containing chlorophyll and a semi-fluid stroma that absorb sunlight to carry out photosynthesis.

Chromoplasts

Plastids containing non-green pigments (yellow, orange, or red) that give bright colours to flowers and fruits to attract pollinators and seed dispersers.

Leucoplasts

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

Vacuole

A fluid-filled organelle surrounded by a single membrane containing cell sap that stores water, minerals, and wastes, maintaining pressure in plant cells.

Mitosis

A common type of cell division that produces two genetically identical daughter cells from a single parent cell with the same number of chromosomes.

Meiosis

A two-step cell division process occurring in reproductive organs that forms four gametes, each containing half the number of chromosomes of the parent cell.

Arun Kumar Sharma

A famous Indian scientist and botanist known for his contributions to chromosome study, plant taxonomy, evolution, and development.

Cell Culture

The process of growing plant or animal cells outside the body in a nutrient-rich medium under controlled, sterile conditions.

Cell Theory

A unifying principle formulated by Schleiden, Schwann, and Virchow stating that all living organisms are made of cells, the cell is the basic functional unit, and all cells arise from pre-existing cells.

Gottlieb Haberlandt

An Austrian botanist who proposed the concept of totipotency in 1902, laying the foundation for Plant Tissue Culture Technology.

Totipotency

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

Contact Inhibition

A cellular regulatory mechanism where cell division stops when animal cells come into physical contact with neighbouring cells.

Programmed Cell Death (PCD)

A genetically regulated and organized process of selective cell destruction essential for normal embryonic development, quality control, and immune function.