cell theory
see unified cell theory
cell wall
rigid cell covering made of various molecules 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
linkage between adjacent epithelial cells that forms 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, that 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