Biology Terminology

A comprehensive set of vocabulary flashcards covering essential biological terms and concepts.

Active Transport

Movement of molecules across a membrane using energy, typically against a concentration gradient.

Cell

The basic structural and functional unit of all living organisms.

Cell Membrane

A semi-permeable barrier that surrounds the cell, controlling entry and exit of substances.

Cell Wall

A rigid outer layer found in plant, fungal, and some bacterial cells that provides structural support.

Cellulose

A polysaccharide that makes up the cell wall in plants, providing rigidity and strength.

Centrioles

Cylindrical structures involved in cell division, helping organize the mitotic spindle.

Chitin

A structural polysaccharide found in fungal cell walls and exoskeletons of arthropods.

Chloroplasts

Organelles in plant cells where photosynthesis occurs.

Cholesterol

A lipid molecule that stabilizes cell membranes and is a precursor for steroid hormones.

Concentration Gradient

A difference in the concentration of a substance across a space or membrane.

Cytoplasm

The jelly-like substance within the cell that contains organelles and is the site of many cellular processes.

Cytoskeleton

A network of protein filaments that provides cell shape, support, and aids in movement.

Desmosomes

Cell structures that anchor cells together, providing mechanical strength in tissues.

Endocytosis

The process by which cells engulf external substances, forming vesicles.

Endomembrane System

A group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.

Equilibrium

A state where the concentrations of substances are equal across a membrane.

Eukaryote

Organisms whose cells contain a nucleus and membrane-bound organelles.

Exocytosis

The process by which cells expel materials using vesicles that fuse with the plasma membrane.

Extracellular Matrix

A network of proteins and carbohydrates outside cells that provides structural and biochemical support.

Facilitated Diffusion

Passive transport of molecules across membranes via protein channels or carriers.

Flaccid

A cell that has lost water and turgor pressure, appearing limp.

Fluid Mosaic Model

Describes the cell membrane as a dynamic structure with proteins floating in or on a fluid lipid bilayer.

Gap Junctions

Channels that allow direct communication between adjacent animal cells.

Glycolipid

Lipids with carbohydrate chains that contribute to cell recognition and membrane stability.

Glycoprotein

Proteins with carbohydrate chains that play roles in cell-cell recognition and signaling.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

Homeostasis

The maintenance of a stable internal environment in an organism.

Hypertonic

A solution with a higher solute concentration than the cell, causing water to leave the cell.

Hypotonic

A solution with a lower solute concentration than the cell, causing water to enter the cell.

Integral Protein

Proteins embedded within the lipid bilayer that span the membrane and assist in transport and signaling.

Intermediate Filaments

Cytoskeletal components that provide mechanical support for the cell.

Isotonic

A solution with equal solute concentration to the cell, resulting in no net water movement.

Ligand

A molecule that binds to a receptor to initiate a cellular response.

Lysosomes

Organelles containing digestive enzymes to break down waste and cellular debris.

Microfilaments

Thin protein fibers involved in cell movement and shape.

Microtubules

Hollow tubes that help with cell shape, transport, and division.

Mitochondria

Organelles that produce energy (ATP) through cellular respiration.

Multicellular

Organisms made up of more than one cell, often with specialized functions.

Nuclear Membrane

A double membrane that encloses the nucleus, controlling access to genetic material.

Nuclear Pores

Openings in the nuclear envelope that allow transport of molecules between nucleus and cytoplasm.

Nucleolus

A dense region within the nucleus where ribosome synthesis occurs.

Nucleus

The control center of the cell containing DNA.

Organelle

Specialized structures within a cell that perform distinct functions.

Osmosis

The diffusion of water across a semi-permeable membrane.

Passive Transport

Movement of substances across membranes without energy input.

Peptidoglycan

A polymer that forms the cell wall of most bacteria.

Peripheral Protein

Proteins attached to the exterior or interior surfaces of the membrane.

Peroxisomes

Organelles that break down fatty acids and detoxify harmful substances.

Phospholipid Bilayer

The fundamental structure of cell membranes, composed of two layers of phospholipids.

Plasma Membrane

Another term for the cell membrane; controls what enters and exits the cell.

Plasmodesmata

Channels between plant cells that allow transport and communication.

Prokaryote

Organisms without a nucleus or membrane-bound organelles, like bacteria.

Protein Pumps

Membrane proteins that use energy to transport substances against their concentration gradient.

Receptor

A protein that binds to a specific ligand to trigger a cellular response.

Response

The cellular change or activity triggered by a signal or stimulus.

Ribosomes

Structures that synthesize proteins by translating mRNA.

Rough Endoplasmic Reticulum

ER with ribosomes attached; involved in protein synthesis and processing.

Selective Permeability

The ability of the membrane to allow some substances to pass while blocking others.

Semi Permeability

Similar to selective permeability; allows certain molecules through while restricting others.

Signal Transduction

The process by which a cell converts a signal into a functional response.

Simple Diffusion

Movement of molecules from high to low concentration without energy or assistance.

Smooth Endoplasmic Reticulum

ER without ribosomes; involved in lipid synthesis and detoxification.

Sodium Potassium Pump

A protein pump that maintains cellular ion balance by moving Na⁺ out and K⁺ in.

Solute

The substance dissolved in a solvent to form a solution.

Solution

A homogeneous mixture of solute and solvent.

Solvent

The substance that dissolves the solute, typically water in biological systems.

Surface Area

The total area of the cell membrane affects the rate of diffusion and transport.

Tight Junctions

Cell connections that prevent leakage of materials between cells.

Turgid

A swollen cell due to water intake, common in hypotonic environments.

Turgor Pressure

The pressure exerted by water inside the cell against the cell wall.

Unicellular

Organisms made up of a single cell.

Vacuoles

Membrane-bound sacs for storage, waste disposal and maintaining turgor in plant cells.

Volume

The amount of space inside a cell; affects metabolic efficiency and transport.

Phagocytosis

A type of endocytosis where a cell engulfs large particles or microorganisms, forming a phagosome.

Pinocytosis

A type of endocytosis where a cell ingests extracellular fluid and dissolved solutes through small vesicles.

single transduction

The process by which a cell converts an external signal into a functional response, often involving a cascade of biochemical events.