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Biology Ch. 4
Term | Definition |
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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 | The cell's outer boundary which covers a cell's surface and acts as a barrier between the inside and outside of a cell |
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 a eukaryotic cell, a membrane-bound organelle that contains the cell’s DNA and that has a role in processes such as growth, metabolism, and reproduction |
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 work together to perform body functions |
Phospholipid Bilayer | A double layer of phospholipids which line up so their heads point outward toward the water and their tails point inward, away from the water |
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 Apparatus | 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 |
Flagellum | A ong, 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 cells, that gives plants their characteristic green color, and that reacts with sunlight, carbon dioxide, and water to form carbohydrates |
Cilium | A hairlike structure arranged in tightly packed rows that projects from the surface of some cells |