Glossary: The Cellular Level of Organization

active transport
form of transport across the cell membrane that requires input of cellular energy
describes a molecule that exhibits a difference in polarity between its two ends, resulting in a difference in water solubility
third stage of mitosis (and meiosis), during which sister chromatids separate into two new nuclear regions of a dividing cell
breakdown of cells by their own enzymatic action
lysosomal breakdown of a cell’s own components
cell cycle
life cycle of a single cell, from its birth until its division into two new daughter cells
cell membrane
membrane surrounding all animal cells, composed of a lipid bilayer interspersed with various molecules; also known as plasma membrane
small, self-replicating organelle that provides the origin for microtubule growth and moves DNA during cell division
region of attachment for two sister chromatids
cellular structure that organizes microtubules during cell division
channel protein
membrane-spanning protein that has an inner pore which allows the passage of one or more substances
substance consisting of DNA and associated proteins
condensed version of chromatin
small appendage on certain cells formed by microtubules and modified for movement of materials across the cellular surface
cleavage furrow
contractile ring that forms around a cell during cytokinesis that pinches the cell into two halves
concentration gradient
difference in the concentration of a substance between two regions
final stage in cell division, where the cytoplasm divides to form two separate daughter cells
internal material between the cell membrane and nucleus of a cell, mainly consisting of a water-based fluid called cytosol, within which are all the other organelles and cellular solute and suspended materials
“skeleton” of a cell; formed by rod-like proteins that support the cell’s shape and provide, among other functions, locomotive abilities
clear, semi-fluid medium of the cytoplasm, made up mostly of water
DNA replication
process of duplicating a molecule of DNA
movement of a substance from an area of higher concentration to one of lower concentration
import of material into the cell by formation of a membrane-bound vesicle
endoplasmic reticulum (ER)
cellular organelle that consists of interconnected membrane-bound tubules, which may or may not be associated with ribosomes (rough type or smooth type, respectively)
export of a substance out of a cell by formation of a membrane-bound vesicle
extracellular fluid (ECF)
fluid exterior to cells; includes the interstitial fluid, blood plasma, and fluid found in other reservoirs in the body
facilitated diffusion
diffusion of a substance with the aid of a membrane protein
appendage on certain cells formed by microtubules and modified for movement
G0 phase
phase of the cell cycle, usually entered from the G1 phase; characterized by long or permanent periods where the cell does not move forward into the DNA synthesis phase
G1 phase
first phase of the cell cycle, after a new cell is born
G2 phase
third phase of the cell cycle, after the DNA synthesis phase
Golgi apparatus
cellular organelle formed by a series of flattened, membrane-bound sacs that functions in protein modification, tagging, packaging, and transport
functional length of DNA that provides the genetic information necessary to build a protein
coating of sugar molecules that surrounds the cell membrane
protein that has one or more carbohydrates attached
family of proteins that associate with DNA in the nucleus to form chromatin
describes two copies of the same chromosome (not identical), one inherited from each parent
describes a substance or structure attracted to water
describes a substance or structure repelled by water
describes a solution concentration that is higher than a reference concentration
describes a solution concentration that is lower than a reference concentration
integral protein
membrane-associated protein that spans the entire width of the lipid bilayer
intermediate filament
type of cytoskeletal filament made of keratin, characterized by an intermediate thickness, and playing a role in resisting cellular tension
entire life cycle of a cell, excluding mitosis
interstitial fluid (IF)
fluid in the small spaces between cells not contained within blood vessels
intracellular fluid (ICF)
fluid in the cytosol of cells
describes a solution concentration that is the same as a reference concentration
region of a centromere where microtubules attach to a pair of sister chromatids
molecule that binds with specificity to a specific receptor molecule
membrane-bound cellular organelle originating from the Golgi apparatus and containing digestive enzymes
messenger RNA (mRNA)
nucleotide molecule that serves as an intermediate in the genetic code between DNA and protein
metaphase plate
linear alignment of sister chromatids in the center of the cell, which takes place during metaphase
second stage of mitosis (and meiosis), characterized by the linear alignment of sister chromatids in the center of the cell
the thinnest of the cytoskeletal filaments; composed of actin subunits that function in muscle contraction and cellular structural support
the thickest of the cytoskeletal filaments, composed of tubulin subunits that function in cellular movement and structural support
one of the cellular organelles bound by a double lipid bilayer that function primarily in the production of cellular energy (ATP)
division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed
mitotic phase
phase of the cell cycle in which a cell undergoes mitosis
mitotic spindle
network of microtubules, originating from centrioles, that arranges and pulls apart chromosomes during mitosis
change in the nucleotide sequence in a gene within a cell’s DNA
nuclear envelope
membrane that surrounds the nucleus; consisting of a double lipid-bilayer
nuclear pore
one of the small, protein-lined openings found scattered throughout the nuclear envelope
small region of the nucleus that functions in ribosome synthesis
cell’s central organelle; contains the cell’s DNA
any of several different types of membrane-enclosed specialized structures in the cell that perform specific functions for the cell
diffusion of molecules down their concentration across a selectively permeable membrane
passive transport
form of transport across the cell membrane that does not require input of cellular energy
peripheral protein
membrane-associated protein that does not span the width of the lipid bilayer, but is attached peripherally to integral proteins, membrane lipids, or other components of the membrane
membrane-bound organelle that contains enzymes primarily responsible for detoxifying harmful substances
endocytosis of large particles
endocytosis of fluid
chain of amino acids linked by peptide bonds
simultaneous translation of a single mRNA transcript by multiple ribosomes
first stage of mitosis (and meiosis), characterized by breakdown of the nuclear envelope and condensing of the chromatin to form chromosomes
reactive oxygen species (ROS)
a group of extremely reactive peroxides and oxygen-containing radicals that may contribute to cellular damage
receptor-mediated endocytosis
endocytosis of ligands attached to membrane-bound receptors
protein molecule that contains a binding site for another specific molecule (called a ligand)
ribosomal RNA (rRNA)
RNA that makes up the subunits of a ribosome
cellular organelle that functions in protein synthesis
S phase
stage of the cell cycle during which DNA replication occurs
selective permeability
feature of any barrier that allows certain substances to cross but excludes others
sister chromatid
one of a pair of identical chromosomes, formed during DNA replication
sodium-potassium pump
(also, Na+/K+ ATP-ase) membrane-embedded protein pump that uses ATP to move Na+ out of a cell and K+ into the cell
somatic cell
all cells of the body excluding gamete cells
stem cell
cell that is oligo-, multi-, or pleuripotent that has the ability to produce additional stem cells rather than becoming further specialized
final stage of mitosis (and meiosis), preceding cytokinesis, characterized by the formation of two new daughter nuclei
process of producing an mRNA molecule that is complementary to a particular gene of DNA
transfer RNA (tRNA)
molecules of RNA that serve to bring amino acids to a growing polypeptide strand and properly place them into the sequence
process of producing a protein from the nucleotide sequence code of an mRNA transcript
membrane-bound structure that contains materials within or outside of the cell