Cell Theory
Cell theory states that living things are composed of one or more cells, that the cell is the basic unit of life, and that cells arise from existing cells.
Eukaryote
Eukaryote, any cell or organism that possesses a clearly defined nucleus. The eukaryotic cell has a nuclear membrane that surrounds the nucleus, in which the well-defined chromosomes
Prokaryote
a microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles.
Organelle
any of a number of organized or specialized structures within a living cell.
flagella
a slender threadlike structure, especially a microscopic appendage that enables many protozoa, bacteria, spermatozoa, etc. to swim.
cilia
Cilia are slender, microscopic, hair-like structures or organelles that extend from the surface of nearly all mammalian cells. They are primordial.
Passive transport
Passive transport is a naturally-occurring phenomenon and does not require the cell to exert any of its energy to accomplish the movement. In passive transport, substances move from an area of higher concentration to an area of lower concentration.
Concentration gradient
A concentration gradient occurs when the concentration of particles is higher in one area than another. In passive transport, particles will diffuse down a concentration gradient, from areas of higher concentration to areas of lower concentration, until they are evenly spaced.
Diffusion
the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration. The difference in the concentrations of the molecules in the two areas is called the concentration gradient.
osmosis
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane
Hypertonic solution
solution that contains more dissolved particles (such as salt and other electrolytes) than is found in normal cells and blood.
Hypotonic solution
A hypotonic solution has a lower concentration of solutes than another solution. In biology, a solution outside of a cell is called hypotonic if it has a lower concentration of solutes relative to the cytosol. Due to osmotic pressure, water diffuses into the cell, and the cell often appears turgid, or bloated.
Isotonic solution
An isotonic solution is one that has the same osmolarity, or solute concentration, as another solution. If these two solutions are separated by a semipermeable membrane, water will flow in equal parts out of each solution and into the other.
Active transport
the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
Endocytosis
the taking in of matter by a living cell by invagination of its membrane to form a vacuole.
Exocytosis
a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
