36 Key Terms

cell theory
see unified cell theory
cell wall
rigid cell covering comprised 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 that serves as an organizing center for microtubules
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 chromosomes’ building material
chromosome
structure within the nucleus that comprises chromatin that contains DNA, the hereditary material
cilium
(plural = cilia) short, hair-like structure that extends from the plasma membrane in large numbers and functions to move an entire cell or move substances along the cell’s outer surface
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
protein fiber network that collectively maintains the cell’s shape, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently
cytosol
the cytoplasm’s gel-like material 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 an electron beam that passes and bends 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 secreted from animal or fungal 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 moves 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 comprised of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution
intermediate filament
cytoskeletal component, comprised of several fibrous protein intertwined strands, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures
light microscope
an instrument that magnifies an object using a beam of visible light that passes and bends 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
the cytoskeleton system’s narrowest element; it provides rigidity and shape to the cell and enables cellular movements
microscope
an instrument that magnifies an object
microtubule
the cytoskeleton system’s widest element; 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 producing ATP, the cell’s main energy-carrying molecule
nuclear envelope
double-membrane structure that constitutes the nucleus’s outermost portion
nucleoid
central part of a prokaryotic cell’s central part where the chromosome is located
nucleolus
darkly staining body within the nucleus that is responsible for assembling ribosome subunits
nucleoplasm
semi-solid fluid inside the nucleus that contains the chromatin and nucleolus
nucleus
cell organelle that houses the cell’s DNA and directs ribosome and protein synthesis
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, and separates the cell’s internal content from its surrounding environment
plasmodesma
(plural = plasmodesmata) channel that passes between adjacent plant cells’ cell walls, connects their cytoplasm, and allows transporting of materials 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
protein adherence that creates a firm seal between two adjacent animal cells
unified cell theory
a biological concept that states that one or more cells comprise all organisms, 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

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Biology 2e Part I, 2nd edition Copyright © 2022 by LOUIS: The Louisiana Library Network is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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