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| Cell | The smallest biological unit capable of carrying out all of the fundamental activities of life. The basic unit of structure and function of any living thing. |
| Cell Membrane | The thin, flexible layer that surrounds a cell and which controls all that enters and leaves the cell. |
| Cell Wall | In plant and bacterial cells, the outermost nonliving cellulose layer that surrounds the entire cell, including the cell membrane. |
| Centriole | In animal cells, a structure outside the nucleus that organizes the spindle fibers during cell reproduction. |
| Centrosome | Another name for the centriole. |
| Chlorophyll | A green pigment found in the chloroplasts of plant cells that is essential for photosynthesis. |
| Chloroplasts | The chlorophyll-containing organelles found in the cytoplasm of plant and algae cells. |
| Chromatin | The coils of DNA and protein that condense to form chromosomes. Chromatin can be thought of as chromosomes with no distinct shape. |
| Chromosomes | Distinct wormlike cell structures formed from chromatin during cell reproduction. |
| Contractile Vacuoles | Large sacs found in the cells of certain protozoans that remove the water that has accumulated inside the cell by pumping it to the outside of the cell. |
| Cilia | Hairlike structures found on the outside of certain cells. The protozoans called ciliates use cilia to propel themselves through the water in which they live. |
| Cytoplasm | That part of a cell's protoplasm that lies outside of its nucleus. |
| Deoxyribonucleic Acid (DNA) | A large and very complex biochemical that stores the information needed to construct proteins and that carries the genetic information about an organism. |
| DNA | The abbreviation for deoxyribonucleic acid. |
| Endoplasmic Reticulum | The intricate system of tubes leading from the nuclear membrane into the cytoplasm that is involved in transporting proteins. |
| Enzyme | A special class of proteins that control the rates of biochemical reactions. |
| Flagellum | A long, whiplike cell structure used to propel sperm cells as well as the cells of the protozoans known as flagellates. |
| Food Vacuoles | The sacs where food particles are digested that are found in the cytoplasm of protozoan cells. |
| Gene | The basic unit of heredity, made up of a specific region on a DNA molecule. Also a specific region of a DNA molecule that holds the code for one specific protein. |
| Golgi Apparatus | A subcellular organelle involved inpackaging proteins for export from the cell. |
| Lysosomes | In animal cells, the organelles where large food molecules are broken down into smaller, more useful, food molecules. |
| Microtubules | Tiny tubules inside the cell that form the cell's internal "cytoskeleton" and that help rearrange structures inside the cell. |
| Mitochondria | The organelles known as the "power houses of the cell" where the stored energy of food is made available for use within the cell. |
| Multicellular | A word used to describe organisms made up of many cells. |
| Nuclear Membrane | A layer inside the cell that surrounds the nucleus and contains many tiny pores. |
| Nucleus | A large structure within the cell that contains chromatin, the nucleolus, and is surrounded by a nuclear membrane. |
| Nucleolus | The "little nucleus" found inside the nucleus which is made up of RNA and protein. |
| Organelle | A tiny cell structure; a miniature organ. Ribosomes, mitochondria, and chloroplasts are all organelles. |
| Phagocytosis | A method by which cells take in food by surrounding and engulfing it. Amebae and white blood cells take in food by this method. |
| Photosynthesis | The process by which plant cells make food and oxygen from water, carbon dioxide, and sunlight. |
| Plasma Membrane or Plasmalemma | Another name for the cell membrane. |
| Protein | A class of biochemicals made up of amino acids that can be important in building and repairing cells or in controlling chemical reactions inside the cell. |
| Protoplasm | All the living materials inside a cell. |
| Ribonucleic Acid (RNA) | A class of nucleic acids that can be used either in reading the genetic information on the DNA or in guiding the process of making proteins. |
| Ribosomes | The organelles where proteins are assembled. |
| RNA | The abbreviation for ribonucleic acid. |
| Spindle Fibers | Microtubules visible during cell division that are involved in separating chromosomes into two separate identical groups. |
| Tissue | Layers of closely related cells that work together to perform a specific function, such as muscle tissue, liver tissue, nervous tissue, etc. |
| Unicellular | An organism composed of just one cell. |
