Chapter 2: Cell—The Building Block of Life

Vocabulary flashcards covering the discovery, structure, functions, and division of cells as discussed in Grade 9 Biology.

Thermophiles

Heat-loving, unicellular bacteria that live in extreme environments such as the hot springs of Puga Valley.

Cell

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

Tissue

A group of similar cells that work together to perform similar functions.

Limit of resolution

The ability of the human eye to see two very close objects as separate and distinct; for the human eye, this is approximately $0.1\,mm$.

Robert Hooke

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

Resolution

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

Contrast

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

Nanometre (nm)

A unit of length equal to one-billionth of a metre, or $0.000001\,mm$.

Cell membrane

A thin, selectively permeable boundary that surrounds a cell and protects its contents, also known as the plasma membrane.

Osmosis

The movement of water through 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 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 inside the cell, causing the cell to swell.

Hypertonic solution

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

Fluid-mosaic model

A model of the cell membrane consisting of a lipid bilayer with embedded proteins that can move sideways, flip, and rotate.

Cell wall

A rigid, permeable additional layer outside the cell membrane found in plants, fungi, and bacteria that provides structural 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 that fills the interior of the cell and contains organelles.

Organelles

Sub-cellular components within the cytoplasm that perform specific jobs for the cell, most visible only with an electron microscope.

Prokaryotic cells

Cells that lack a well-defined nucleus and membrane-bound organelles, with genetic material located in the nucleoid.

Eukaryotic cells

Complex cells that contain a well-defined nucleus and several membrane-bound organelles.

Cytoskeleton

A network of fine fibres in eukaryotic cells that providing structural support, maintaining cell shape, and enabling movement.

Cell inclusions

Stored materials in the cytoplasm such as starch, calcium oxalate crystals, or silica.

Viruses, viroids, and prions

Acellular infectious agents that are too small to be seen under a light microscope.

Nucleus

The house of coded instructions in a cell, containing genetic material and surrounded by a double-layered nuclear membrane.

Nucleolus

A dense round body within the nucleus where ribosomal subunits are synthesized.

DNA (Deoxyribonucleic acid)

Molecules that contain the genetic information for the inheritance of characters from parents to the next generation.

Genes

The functional segments of DNA molecules.

Chromatin

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

Ribosomes

Tiny structures that serve as the protein factories of the cell, found freely in cytoplasm or attached to the ER.

Rough Endoplasmic Reticulum (RER)

A network with ribosomes attached to its surface involved in the synthesis and secretion of proteins.

Smooth Endoplasmic Reticulum (SER)

A part of the ER without ribosomes involved in the synthesis and storage of fats (lipids) and hormones.

Golgi apparatus

Stacks of flattened, sac-like structures that function as packaging and shipping centers for proteins and lipids.

Lysosomes

Single membrane-bound sacs filled with enzymes that act as the cell's clean-up system.

Mitochondria

The powerhouses of the cell where cellular respiration occurs to release energy in the form of ATP.

ATP (Adenosine Triphosphate)

The energy currency of the cell used for most cellular activities.

Cristae

Finger-like projections formed by the folding of the inner mitochondrial membrane to increase surface area.

Chloroplasts

Double-membrane-bound plastids containing chlorophyll where the process of photosynthesis takes place.

Chromoplasts

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

Leucoplasts

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

Vacuoles

Storage organelles for water, minerals, and waste; in plants, they help maintain cell firmness through cell sap.

Mitosis

A type of cell division resulting in two genetically identical daughter cells, essential for growth and repair.

Meiosis

A two-step cell division process in reproductive organs that produces four daughter cells (gametes) with half the original chromosome number.

Cell culture

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

Cell Theory

The unifying 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 where cell division stops when cells come in contact with neighbouring cells, a control mechanism lost in cancer cells.

Programmed Cell Death (PCD)

A genetically regulated and organized process of selective cell destruction.

Totipotency

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