Cell Biology

Cell Theory

A fundamental concept in biology stating: 1) All living things are made of cells, 2) Cells are the basic unit of life, 3) New cells arise from existing cells.

Prokaryotes

Single-celled organisms that lack a nucleus and membrane-bound organelles, e.g., bacteria.

Eukaryotes

Organisms whose cells contain a nucleus and membrane-bound organelles. They can be unicellular or multicellular.

Organelle

A specialized subunit within a cell that has a specific function, e.g., mitochondria, nucleus.

Cytoplasm

The gel-like substance within a cell that contains organelles and is the site of metabolic processes.

Nucleus

The membrane-bound organelle that contains the cell's genetic material (DNA) and controls cellular activities.

Ribosomes

Cellular structures that synthesize proteins; can be free in the cytoplasm or bound to the endoplasmic reticulum.

Cell Membrane

A phospholipid bilayer that surrounds the cell, controlling the entry and exit of substances.

Cell Wall

A rigid layer surrounding the cell membrane in plants, fungi, and bacteria, providing structure and protection.

Mitochondrion

Double-membraned organelle responsible for ATP production through aerobic respiration.

Chloroplast

An organelle found in plant cells that conducts photosynthesis, converting light energy into chemical energy.

Vacuole

A membrane-bound cavity within a cell that stores substances and helps maintain cell turgidity.

Cilia

Short, hair-like structures that protrude from the cell surface and are involved in movement or sensory functions.

Flagella

Long, whip-like structures used by some cells for movement.

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration.

Facilitated Diffusion

A process where molecules bypass the lipid bilayer via protein channels without the use of energy.

Active Transport

The movement of molecules across a cell membrane against their concentration gradient, requiring energy.

Tissue

A group of cells that work together to perform a specific function.

Stem Cells

Undifferentiated cells that can divide and give rise to specialized cell types.

Chromatin

A complex of DNA and proteins found in the nucleus that condenses to form chromosomes during cell division.

Meiosis

A type of cell division that produces haploid gametes with half the chromosome number, leading to genetic diversity.

Mitosis

A type of cell division that results in two genetically identical daughter cells, maintaining chromosome number.

Hydrophobic

Substances that do not mix well with water, typically nonpolar molecules.

Hydrophilic

Substances that readily dissolve in water, typically polar molecules or ions.

Amphipathic

Molecules that have both hydrophilic and hydrophobic regions, such as phospholipids in cell membranes.

Glycoproteins

Proteins with carbohydrate groups attached, important for cell recognition and signaling.

Glycolipids

Lipids with a carbohydrate component that contribute to cell membrane structure and recognition.

Cytoskeleton

A network of protein filaments and tubules that maintain cell shape, provide mechanical support, and facilitate movement.

Tetrad

A structure containing four chromatids formed during prophase I of meiosis by the pairing of homologous chromosomes.

Crossing Over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division.

Trisomy

A genetic disorder characterized by the presence of an extra chromosome, leading to developmental issues.

Gametes

Reproductive cells (sperm and ova) that contain half the genetic information of an organism.

Zygote

The fertilized egg cell resulting from the union of a sperm and an ovum.

Homeostasis

The ability of a cell or organism to maintain stable internal conditions despite external changes.

Differentiation

The process by which unspecialized cells develop into specialized cells with distinct functions.

Cell Division

The process by which a parent cell divides into two or more daughter cells, including mitosis and meiosis.

Cellular Respiration

The metabolic processes that convert biochemical energy from nutrients into ATP, releasing waste products.