Definitions

= ** D e f i n i t i o n s ** = __**Cell-**__ in biology, the smallest unit that can perform all life processes;cells are covered by a membrane and have DNA and cytoplasm.

**__Nucleus-__** a central or fundamental part or thing around which others are grouped;core.

**__Nucleolus-__** a conspicuous, rounded body within the nucleus of a cell.

**__Golgi Body/Apparatus-__** An organelle, consisting of layers of flattened sacs, that takes up and processes secetory and synthetic products from the end oplasmic reticulum and then either releases the finished products iinto carious parts of the cell cyto plasm or ssecretes them to the outside of the cell.

**__Endoplasmic Reticulum-__**A network of tubular membranes within the cytoplasm of the cell, occuring either with a smooth surface(smooth endoplasmic reeticulum) or studded with ribosomes(rough endoplasmic reticulum) involved in the transport of materials.

**__Cell Membrane-__** the semipermeable membrane enclosing the cytoplasm of a cell.

**__Lysosomes-__** a cell organelle containing enzymes that digest particles and that disintegrate the cell after its death.

**__Vacuoles-__** A membrane-bound cavity within a cell, often containing a waterly liquid of secretion.

**__Ribosome-__** a tiny, somewhat mitten-shaped organelle occuring in great numbers in the cell cytoplasm either freely, in small clusters, or attached to the outer surfaces of endoplasmic reticula, and functioning as the site of protein manufacture.

**__Chloroplast-__** a plastid containing chlorophyll and other pigments, occuring in plants and algae that carry out photosynthesis.

**__Cell Wall-__** the defenite boundary or wall that is part of the outer structure of certain cells, such as a plant cell.

__**Mitochordria-**__ an organelle in the cytoplasm of cells that functions in energy production.

**__Cytoplasm-__** the cell substance between the cell membrane and the nucleus, containing the cytosol, organelles, cytoskeletion, and various particles.

**__Organelle-__** one of the small bodies in a cell's cytoplasm that are specialized to perform a specific function.

__**Unicellular-**__ an organism made of a single cell.

**__Tissue-__** a group of similar cells that perform a common function.

__**Organ-**__ a collection of tissues that carry out a specialized function in the body.

__**Organ System-**__ a group of organs that work together to perform body functions.

**__Nuclear Membrane-__** the double membrane surrounding the nucleus within a cell.

**__Centrosome-__** a small region near the nucleus in the cell cytoplasm, containing the centrioles.