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Biology Ch. 4

TermDefinition
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
Created by: HuffmanV20