3.8: Key Terms

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3.8: Key Terms

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(Eg. "Genetic, Hereditary, DNA ...")	(Eg. "Relating to genes or heredity")		The infamous double helix	https://bio.libretexts.org/	CC-BY-SA; Delmar Larsen

Glossary Entries

Word(s)	Definition	Image	Caption	Link	Source
active transport	form of transport across the cell membrane that requires input of cellular energy
amphipathic	describes a molecule that exhibits a difference in polarity between its two ends, resulting in a difference in water solubility
anaphase	third stage of mitosis (and meiosis), during which sister chromatids separate into two new nuclear regions of a dividing cell
anticodon	consecutive sequence of three nucleotides on a tRNA molecule that is complementary to a specific codon on an mRNA molecule
autolysis	breakdown of cells by their own enzymatic action
autophagy	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
centriole	small, self-replicating organelle that provides the origin for microtubule growth and moves DNA during cell division
centromere	region of attachment for two sister chromatids
centrosome	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
checkpoint	progress point in the cell cycle during which certain conditions must be met in order for the cell to proceed to a subsequence phase
chromatin	substance consisting of DNA and associated proteins
chromosome	condensed version of chromatin
cilia	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
codon	consecutive sequence of three nucleotides on an mRNA molecule that corresponds to a specific amino acid
concentration gradient	difference in the concentration of a substance between two regions
cyclin	one of a group of proteins that function in the progression of the cell cycle
cyclin-dependent kinase (CDK)	one of a group of enzymes associated with cyclins that help them perform their functions
cytokinesis	final stage in cell division, where the cytoplasm divides to form two separate daughter cells
cytoplasm	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
cytoskeleton	“skeleton” of a cell; formed by rod-like proteins that support the cell’s shape and provide, among other functions, locomotive abilities
cytosol	clear, semi-fluid medium of the cytoplasm, made up mostly of water
diffusion	movement of a substance from an area of higher concentration to one of lower concentration
diploid	condition marked by the presence of a double complement of genetic material (two sets of chromosomes, one set inherited from each of two parents)
DNA polymerase	enzyme that functions in adding new nucleotides to a growing strand of DNA during DNA replication
DNA replication	process of duplicating a molecule of DNA
electrical gradient	difference in the electrical charge (potential) between two regions
endocytosis	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)
exocytosis	export of a substance out of a cell by formation of a membrane-bound vesicle
exon	one of the coding regions of an mRNA molecule that remain after splicing
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
flagellum	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
gene	functional length of DNA that provides the genetic information necessary to build a protein
gene expression	active interpretation of the information coded in a gene to produce a functional gene product
genome	entire complement of an organism’s DNA; found within virtually every cell
glycocalyx	coating of sugar molecules that surrounds the cell membrane
glycoprotein	protein that has one or more carbohydrates attached
Golgi apparatus	cellular organelle formed by a series of flattened, membrane-bound sacs that functions in protein modification, tagging, packaging, and transport
helicase	enzyme that functions to separate the two DNA strands of a double helix during DNA replication
histone	family of proteins that associate with DNA in the nucleus to form chromatin
homologous	describes two copies of the same chromosome (not identical), one inherited from each parent
hydrophilic	describes a substance or structure attracted to water
hydrophobic	describes a substance or structure repelled by water
hypertonic	describes a solution concentration that is higher than a reference concentration
hypotonic	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
interphase	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
intron	non-coding regions of a pre-mRNA transcript that may be removed during splicing
isotonic	describes a solution concentration that is the same as a reference concentration
kinetochore	region of a centromere where microtubules attach to a pair of sister chromatids
ligand	molecule that binds with specificity to a specific receptor molecule
lysosome	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	second stage of mitosis (and meiosis), characterized by the linear alignment of sister chromatids in the center of the cell
metaphase plate	linear alignment of sister chromatids in the center of the cell, which takes place during metaphase
microfilament	the thinnest of the cytoskeletal filaments; composed of actin subunits that function in muscle contraction and cellular structural support
microtubule	the thickest of the cytoskeletal filaments, composed of tubulin subunits that function in cellular movement and structural support
mitochondrion	one of the cellular organelles bound by a double lipid bilayer that function primarily in the production of cellular energy (ATP)
mitosis	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
multipotent	describes the condition of being able to differentiate into different types of cells within a given cell lineage or small number of lineages, such as a red blood cell or white blood cell
mutation	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
nucleolus	small region of the nucleus that functions in ribosome synthesis
nucleosome	unit of chromatin consisting of a DNA strand wrapped around histone proteins
nucleus	cell’s central organelle; contains the cell’s DNA
oligopotent	describes the condition of being more specialized than multipotency; the condition of being able to differentiate into one of a few possible cell types
organelle	any of several different types of membrane-enclosed specialized structures in the cell that perform specific functions for the cell
osmosis	diffusion of water molecules down their concentration gradient 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
peroxisome	membrane-bound organelle that contains enzymes primarily responsible for detoxifying harmful substances
phagocytosis	endocytosis of large particles
pinocytosis	endocytosis of fluid
pluripotent	describes the condition of being able to differentiate into a large variety of cell types
polypeptide	chain of amino acids linked by peptide bonds
polyribosome	simultaneous translation of a single mRNA transcript by multiple ribosomes
promoter	region of DNA that signals transcription to begin at that site within the gene
prophase	first stage of mitosis (and meiosis), characterized by breakdown of the nuclear envelope and condensing of the chromatin to form chromosomes
proteome	full complement of proteins produced by a cell (determined by the cell’s specific gene expression)
reactive oxygen species (ROS)	a group of extremely reactive peroxides and oxygen-containing radicals that may contribute to cellular damage
receptor	protein molecule that contains a binding site for another specific molecule (called a ligand)
receptor-mediated endocytosis	endocytosis of ligands attached to membrane-bound receptors
ribosomal RNA (rRNA)	RNA that makes up the subunits of a ribosome
ribosome	cellular organelle that functions in protein synthesis
RNA polymerase	enzyme that unwinds DNA and then adds new nucleotides to a growing strand of RNA for the transcription phase of 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
spliceosome	complex of enzymes that serves to splice out the introns of a pre-mRNA transcript
splicing	the process of modifying a pre-mRNA transcript by removing certain, typically non-coding, regions
stem cell	cell that is oligo-, multi-, or pleuripotent that has the ability to produce additional stem cells rather than becoming further specialized
telophase	final stage of mitosis (and meiosis), preceding cytokinesis, characterized by the formation of two new daughter nuclei
totipotent	embryonic cells that have the ability to differentiate into any type of cell and organ in the body
transcription	process of producing an mRNA molecule that is complementary to a particular gene of DNA
transcription factor	one of the proteins that regulate the transcription of genes
transfer RNA (tRNA)	molecules of RNA that serve to bring amino acids to a growing polypeptide strand and properly place them into the sequence
translation	process of producing a protein from the nucleotide sequence code of an mRNA transcript
triplet	consecutive sequence of three nucleotides on a DNA molecule that, when transcribed into an mRNA codon, corresponds to a particular amino acid
unipotent	describes the condition of being committed to a single specialized cell type
vesicle	membrane-bound structure that contains materials within or outside of the cell

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