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Active Transport

Energy-requiring process that moves material across a cell membrane against a concentration difference.

Adenosine Triphosphate (ATP)

The major energy currency of the cell, providing the energy for most of the energy-consuming activities of the cell.


The basic structural and functional unit of all organisms.

Cell Theory

The theory that cells form the fundamental structural and functional units of all living organisms.

Cell Wall

A thin membrane around the cytoplasm of a cell.


An organelle found in plant and algae cells where photosynthesis occurs.


A hairlike projection from the surface of a cell.


Strengthening the concentration (as of a solute in a mixture) by removing extraneous material.


The branch of biology that studies the structure and function of cells.


Process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated.


Process by which a cell takes material into the cell by infolding of the cell membrane.

Endoplasmic Reticulum

Cell organelle that creates a network of membranes found through the whole cell.


Equality of distribution of chemicals inside and outside of a cell.

Eukaryotic Cell

Cell with a nucleus (surrounded by its own membrane) and other internal organelles.


process by which a cell releases large amounts of material

Facilitated Diffusion

Movement of specific molecules across cell membranes through protein channels.


A lash-like appendage used for locomotion.

Golgi Apparatus

A net-like structure in the cytoplasm of animal cells (especially in those cells that produce secretions).


Having a higher osmotic pressure than a comparison solution.


Having the same or equal osmotic pressure.


Cell organelle filled with enzymes needed to break down certain materials in the cell.


A pliable sheet of tissue that covers or lines or connects organs or cells of animals that allow substances to move in and/or out of the cell.


Solid rod of protein, thinner than a microtubule, that enables a cell to move or change shape.


Powerhouse of the cell, organelle that is the site of ATP production.


Straight, hollow tube of proteins that gives rigidity, shape, and organization to a cell.

Nuclear Envelope

Layer of two membranes that surrounds the nucleus of a cell.


Small, dense region within most nuclei in which the assembly of proteins begins.


A tiny cell structure that carries out a specific function within the cell.


Diffusion of water through a selectively permeable membrane.

Passive Transport

Transport of a substance across a cell membrane by diffusion.

Permeable Membrane

A membrane that allows for diffusion of certain solutes and water.

Phospholipid Bilayer

A double layer of phospholipids that makes up plasma and organelle membranes.

Plasma Membrane

A thin membrane around the cytoplasm of a cell.

Prokaryotic Cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.


An organelle in the cytoplasm of a living cell.

Selectively Permeable

A property of cell membranes that allows some substances to pass through, while others cannot.


Cell organelle that stores materials such as water, salts, proteins, and carbohydrates.


A membrane bound sac that contains materials involved in transport of the cell.

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