Data

Copy and paste the text below. It is read-only. Select All

cell in biology, the smallest unit that can perform all life processes; cells are covered by a membrane and contain DNA and cytoplasm cell theory the theory that states that all living things are made up of cells, that cells are the basic units of organisms, that each cell in a multicellular organism has a specific job, and that cells come only from existing cells plasma membrane or cell membrane, the cell's outer boundary cytoplasm the region of the cell within the membrane that includes the fluid, the cytoskeleton, and all of the organelles except the nucleus cytosol the soluble portion of the cytoplasm, which includes molecules and small particles, such as ribosomes, but not the organelles covered with membranes nucleus in physical science, an atom's central region, which is made up of protons and neutrons prokaryote a single-celled organism that does not have a nucleus or membrane-bound organelles; examples are archaea and bacteria eukaryote an organism made up of cells that have a nucleus enclosed by a membrane, multiple chromosomes, and a mitotic cycle; eukaryotes include protists, animals, plants, and fungi but not archaea or bacteria organelle one of the small bodies that are found in the cytoplasm of a cell and that are specialized to perform a specific function tissue a group of similar cells that perform a common function organ a collection of tissues that carry out a specialized function of the body organ system a group of organs that accomplish related tasks tissue a group of similar cells that perform a common function phospholipid a double layer of phospholipids that makes up plasma and organelle membranes chromosome in a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; in a prokaryotic cell, the main ring of DNA nuclear envelope the double membrane that surrounds the nucleus of a eukaryotic cell nucleolus the part of the eukaryotic nucleus where ribosomal RNA is synthesized ribosome a cell organelle composed of RNA and protein; the site of protein synthesis mitochondrion in eukaryotic cells, the cell organelle that is surrounded by two membranes and that is the site of cellular respiration, which produces ATP endoplasmic reticulum a system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids Golgi complex a cell organelle that helps make and package materials to be transported out of the cell lysosome a cell organelle that contains digestive enzymes cytoskeleton the cytoplasmic network of protein filaments that plays an essential role in cell movement, shape, and division microtubule one of the small, tubular fibers composed of the protein tubulin that are found in the cytoplasm of eukaryotic cells, that compose the cytoskeleton, and that play a role in cell structure and movement microfilament a fiber found inside eukaryotic cells that is composed mainly of the protein actin and that has a role in cell structure and movement cilium a hairlike structure arranged in tightly packed rows that projects from the surface of some cells flagellum a long, hairlike structure that grows out of a cell and enables the cell to move centriole an organelle that is active during mitosis cell wall a rigid structure that surrounds the cell membrane and provides support to the cell central vacuole a large cavity or sac that is found in plant cells or protozoans and that contains air or partially digested food plastid an organelle of plant cells that contains specific substances and performs specific functions for the cell chloroplast an organelle found in plant and algae cells where photosynthesis occurs thylakoid a membrane system found within chloroplasts that contains the components for photosynthesis chlorophyll a green pigment that is present in most plant and algae cells and some bacteria, that gives plants their characteristic green color, and that absorbs light to provide energy for photosynthesis