Sections
Key Terms
Key Terms
- cell theory
- see unified cell theory
- cell wall
- rigid cell covering made of cellulose that protects the cell, provides structural support, and gives shape to the cell
- central vacuole
- large plant cell organelle that regulates the cell’s storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation
- centrosome
- region in animal cells made of two centrioles
- chlorophyll
- green pigment that captures the light energy that drives the light reactions of photosynthesis
- chloroplast
- plant cell organelle that carries out photosynthesis
- chromatin
- protein-DNA complex that serves as the building material of chromosomes
- chromosome
- structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material
- cilium
- (plural = cilia) short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell
- cytoplasm
- entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals
- cytoskeleton
- network of protein fibers that collectively maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently
- cytosol
- gel-like material of the cytoplasm in which cell structures are suspended
- desmosome
- linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments
- electron microscope
- an instrument that magnifies an object using a beam of electrons passed and bent through a lens system to visualize a specimen
- endomembrane system
- group of organelles and membranes in eukaryotic cells that work together, modifying, packaging, and transporting lipids and proteins
- endoplasmic reticulum (ER)
- series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids
- eukaryotic cell
- cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs
- extracellular matrix
- material (primarily collagen, glycoproteins, and proteoglycans) secreted from animal cells that provides mechanical protection and anchoring for the cells in the tissue
- flagellum
- (plural = flagella) long, hair-like structure that extends from the plasma membrane and is used to move the cell
- gap junction
- channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate
- Golgi apparatus
- eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution
- intermediate filament
- cytoskeletal component, composed of several intertwined strands of fibrous protein, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures
- light microscope
- an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen
- lysosome
- organelle in an animal cell that functions as the cell’s digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles
- microfilament
- narrowest element of the cytoskeleton system; it provides rigidity and shape to the cell and enables cellular movements
- microscope
- an instrument that magnifies an object
- microtubule
- widest element of the cytoskeleton system; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and cilia
- mitochondria
- (singular = mitochondrion) cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell’s main energy-carrying molecule
- nuclear envelope
- double-membrane structure that constitutes the outermost portion of the nucleus
- nucleoid
- central part of a prokaryotic cell in which the chromosome is found
- nucleolus
- darkly staining body within the nucleus that is responsible for assembling the subunits of the ribosomes
- nucleoplasm
- semi-solid fluid inside the nucleus that contains the chromatin and nucleolus
- nucleus
- cell organelle that houses the cell’s DNA and directs the synthesis of ribosomes and proteins
- organelle
- compartment or sac within a cell
- peroxisome
- small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons
- plasma membrane
- phospholipid bilayer with embedded (integral) or attached (peripheral) proteins; separates the internal content of the cell from its surrounding environment
- plasmodesma
- (plural = plasmodesmata) channel that passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell
- prokaryote
- unicellular organism that lacks a nucleus or any other membrane-bound organelle
- ribosome
- cellular structure that carries out protein synthesis
- rough endoplasmic reticulum (RER)
- region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis
- smooth endoplasmic reticulum (SER)
- region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies certain chemicals (like pesticides, preservatives, medications, and environmental pollutants); and stores calcium ions
- tight junction
- firm seal between two adjacent animal cells created by protein adherence
- unified cell theory
- a biological concept that states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells
- vacuole
- membrane-bound sac, somewhat larger than a vesicle, which functions in cellular storage and transport
- vesicle
- small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus