1
Q
The basic unit from which a living organism is made; an aqueous solution of chemicals, enclosed by a membrane, that has an ability to self-replicate.
A
cell
2
Q
Double-stranded polynucleotide formed from two separate chains of covalently linked deoxyribonucleotides. It serves as the cell’s store of genetic information that is transmitted from generation to generation.
A
DNA
3
Q
Molecule produced by the transcription of DNA; usually single-stranded, it is a polynucleotide composed of covalently linked ribonucleotide subunits. Serves a variety of informational, structural, catalytic, and regulatory functions in cells.
A
RNA
4
Q
Macromolecule built from amino acids that provides cells with their shape and structure and performs most of their activities.
A
protein
5
Q
Process of gradual modification and adaptation that occurs in living organisms over generations.
A
evolution
6
Q
The total genetic information carried by all the chromosomes of a cell or organism; in humans, the total number of nucleotide pairs in the 22 autosomes plus the X and Y chromosomes.
A
genome
7
Q
Instrument for viewing extremely small objects. Some use a focused beam of visible light and are used to examine cells and organelles. Others use a beam of electrons and can be used to examine objects as small as individual molecules.
A
microscope
8
Q
The protein-containing lipid bilayer that surrounds a living cell.
A
plasma membrane
9
Q
Contents of a cell that are contained within its plasma membrane but, in the case of eukaryotic cells, outside the nucleus.
A
cytoplasm
10
Q
Instrument used to visualize a specimen that has been labeled with a fluorescent dye; samples are illuminated with a wavelength of light that excites the dye, causing it to fluoresce.
A
fluorescence microscope
11
Q
Large macromolecular complex, composed of RNAs and proteins, that translates a messenger RNA (mRNA) into a polypeptide chain.
A
ribosome
12
Q
Instrument that passes a beam of electrons through a specimen to reveal and magnify the structures of very small objects, such as organelles and large molecules.
A
electron microscope
13
Q
A discrete structure or subcompartment of a eukaryotic cell that is specialized to carry out a particular function. Examples include mitochondria and the Golgi apparatus.
A
organelle
14
Q
An organism whose cells have a distinct nucleus and cytoplasm.
A
eukaryote
15
Q
Major category of living cells distinguished by the absence of a nucleus; includes the archaea and the eubacteria (commonly called bacteria).
A
prokaryote
16
Q
Microscopic organism that is a member of one of two divisions of prokaryotes; some species cause disease. The term is sometimes used to refer to any prokaryotic microorganism, although the world of prokaryotes also includes archaea, which are only distantly related.
A
bacterium
17
Q
Microscopic organism that is a member of one of the two divisions of prokaryotes; often found in hostile environments such as hot springs or concentrated brine.
A
archaeon
18
Q
In biology, refers to the prominent, rounded structure that contains the DNA of a eukaryotic cell. In chemistry, refers to the dense, positively charged center of an atom.
A
nucleus
19
Q
Long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism; becomes visible as a distinct entity when a plant or animal cell prepares to divide.
A
chromosome
20
Q
Membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells.
A
mitochondrion
21
Q
Specialized organelle in algae and plants that contains chlorophyll and serves as the site for photosynthesis.
A
chloroplast
22
Q
The process by which plants, algae, and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water.
A
photosynthesis
23
Q
Labyrinthine membrane-enclosed compartment in the cytoplasm of eukaryotic cells where lipids and proteins are made.
A
endoplasmic reticulum (ER)
24
Q
Membrane-enclosed organelle in eukaryotic cells that modifies the proteins and lipids made in the endoplasmic reticulum and sorts them for transport to other sites.
A
Golgi apparatus
25
Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as the endoplasmic reticulum and mitochondria. Also used to refer to the cell fraction remaining after membranes, cytoskeletal components, and other organelles have been removed.
cytosol
26
System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules, and intermediate filaments.
cytoskeleton
27
A free-living, nonphotosynthetic, single-celled, motile eukaryote.
protozoan
28
A living thing selected for intensive study as a representative of a large group of species. Examples include the mouse (representing mammals), the yeast (representing a unicellular eukaryote), and E. coli (representing bacteria).
model organism
29
Describes genes, chromosomes, or any structures that are similar because of their common evolutionary origin. Can also refer to similarities between protein sequences or nucleic acid sequences.
homologous
30
A molecule that releases a proton when dissolved in water; this dissociation generates hydronium (H3O+) ions, thereby lowering the pH.
acid
31
The smallest particle of an element that still retains its distinctive chemical properties; consists of a positively charged nucleus surrounded by a cloud of negatively charged electrons.
atom
31
Small organic molecule containing both an amino group and a carboxyl group; it serves as the building block of proteins.
amino acid
32
Activated carrier that serves as the principal carrier of energy in cells; a nucleoside triphosphate composed of adenine, ribose, and three phosphate groups.
ATP
33
Region on the surface of an enzyme that binds to a substrate molecule and catalyzes its chemical transformation.
active site
34
Describes a protein that can exist in multiple conformations depending on the binding of a molecule (ligand) at a site other than the catalytic site; such changes from one conformation to another often alter the protein's activity or ligan affinity.
allosteric
35
Folding pattern, common in many proteins, in which a single polypeptide chain twists around itself to form a rigid cylinder stabilized by hydrogen bonds between every fourth amino acid.
alpha helix
36
The order of the amino acid subunits in a protein chain. Sometimes called the primary structure of a protein.
amino acid sequence
37
Protein produced by B lymphocytes in response to a foreign molecule or invading organism. Binds to the foreign molecule or cell extremely tightly, thereby inactivating it or marking it for destruction.
antibody
38
Molecule or fragment of a molecule that is recognized by an antibody.
antigen
39
Folding pattern found in many proteins in which neighboring regions of the polypeptide chain associate side-by-side with each other through hydrogen bonds to give a rigid, flattened structure.
beta sheet
40
Region on the surface of a protein, typically a cavity or groove, that interacts with another molecule (a ligand) through the formation of multiple noncovalent bonds.
binding site
41
A large aggregate of phase-separated macromolecules that creates a region with a special biochemistry without the use of an encapsulating membrane.
biomolecular condensate
42
Small molecule that binds tightly to an enzyme and helps it to catalyze a reaction.
coenzyme
43
Covalent cross-link formed between the sulfhydryl groups on two cysteine side chains; often used to reinforce a secreted protein's structure or to join two different proteins together.
disulfide bond
44
A protein that catalyzes a specific chemical reaction.
enzyme
45
A form of metabolic control in which the end product of a chain of enzymatic reactions reduces the activity of an enzyme early in the pathway.
feedback inhibition
46
Intracellular signaling protein whose activity is determined by its association with either GTP or GDP. Includes both trimeric G proteins and monomeric GTPases, such as Ras.
GTP-binding protein
47
General term for a small molecule that binds to a specific site on a macromolecule.
ligand
48
Enzyme that severs the polysaccharide chains that form the cell walls of bacteria; found in many secretions including saliva and tears, where it serves as an antibiotic.
lysozyme
49
The end of a polypeptide chain that carries a free a-amino group.
N-terminus
50
Covalent chemical bond between the carbonyl group of one amino acid and the amino group of a second amino acid.
peptide bond
51
Linear polymer composed of multiple amino acids. Proteins are composed of one or more long polypeptide chains.
polypeptide chain
52
Repeating sequence of the atoms (-N-C-C-) that form the core of a protein molecule and to which the amino acid side chains are attached.
polypeptide backbone
53
The amino acid sequence of a protein.
primary structure
54
Macromolecule built from amino acids that provides cells with their shape and structure and performs most of their activities.
protein
55
Segment of a polypeptide chain that can fold into a compact, stable structure and that often carries out a specific function.
protein domain
56
Enzyme that catalyzes the transfer of a phosphate group from ATP to a specific amino acid side chain on a target protein.
protein kinase
57
Enzyme that catalyzes the removal of a phosphate group from a protein, often with high specificity for the phosphorylated site.
protein phosphatase
58
The covalent addition of a phosphate group to a side chain of a protein, catalyzed by a protein kinase; serves as a form of regulation that usually alters the activity or properties of the target protein.
protein phosphorylation
59
Complete structure formed by multiple, interacting polypeptide chains that form a larger protein molecule.
quaternary structure
60
Regular local folding pattern of a polymeric molecule. In proteins, it refers to alpha helices and beta sheets.
secondary structure.
61
Portion of an amino acid not involved in forming peptide bonds; its chemical identity gives each amino acid unique properties.
side chain
62
A molecule on which an enzyme acts to catalyze a chemical reaction.
substrate
63
Complete three-dimensional structure of a fully folded protein.
tertiary structure
64
A family of enzymes (typically multisubunit) that use the energy of ATP hydrolysis to alter the arrangement of nucleosomes in eukaryotic chromosomes, changing the accessibility of the underlying DNA to other proteins.
chromatin-remodeling complex
65
Specialized DNA sequence that allows duplicated chromosomes to be separated during M phase; can be seen as the constricted region of a mitotic chromosome.
centromere
66
Complex of DNA and proteins that makes up the chromosomes in a eukaryotic cell.
chromatin
67
Long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism; becomes visible as a distinct entity when a plant or animal cell prepares to divide.
chromosome
68
A ring-shaped SMC protein complex that organizes interphase chromosomes into a long series of large chromatin loops; in addition, a special subset of cohesins holds together the sister chromatids after DNA has been replicated.
cohesin
69
A ring-shaped SMC protein complex that compacts duplicated chromosomes for segregation by forming both loops and loops within loops.
condensin
70
One of the two main states in which chromatin exists within an interphase cell. Prevalent in gene-rich areas, its less compact structure allows access for proteins involved in transcription.
euchromatin
71
Highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive.
heterochromatin
72
One of a small group of abundant, highly conserved proteins around which DNA wraps to form nucleosomes, structures that represent the most fundamental level of chromatin packing.
histone
73
Enzyme that catalyzes the covalent addition of a small molecule, such as a methyl or acetate group, to a specific amino acid side chain on a histone.
histone-modifying enzyme
74
Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.
nucleolus
75
Beadlike structural unit of a eukaryotic chromosome composed of a short length of DNA wrapped around an octameric core of histone proteins; includes a nucleosomal core particle (DNA plus histone protein) along with a segment of linker DNA that ties the core particles together.
nucleosome
76
A large ring-shaped structure that contains two Structural Maintenance of Chromosomes (SMC) protein subunits at its core; the ring these proteins form is large enough for nucleosomes to pass easily through it. Cohesins and condensins are two major types.
SMC ring complex
77
During protein synthesis, an enzyme that attaches the correct amino acid to a tRNA molecule to form a "charged" aminoacyl-tRNA.
aminoacyl-tRNA synthetase
78
Set of three consecutive nucleotides in a transfer RNA molecule that recognizes, through base-pairing, the three-nucleotide codon on a messenger RNA molecule; this interactions helps to deliver the correct amino acid to a growing polypeptide chain.
anticodon
79
Group of three consecutive nucleotides that specifies a particular amino acid or that starts or stops protein synthesis; applies to the nucleotides in an mRNA or in a coding sequence of DNA.
codon
80
Segment of a eukaryotic gene that is transcribed into RNA and dictates the amino acid sequence of part of a protein.
exon
81
Noncoding sequence within a eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce an mRNA.
intron
82
RNA molecule that specifies the amino acid sequence of a protein.
messenger RNA (mRNA)
83
An RNA molecule that is the final product of a gene and does not code for a protein. These RNAs serve as enzymatic, structural, and regulatory components for a wide variety of processes in the cell.
noncoding RNA
84
The addition of multiple adenine nucleotides to the 3' end of a newly synthesized mRNA molecule.
polyadenylation
85
Enzyme that degrades proteins by hydrolyzing their peptide bonds.
protease
86
RNA molecule that forms the structural and catalytic core of the ribosome.
ribosomal RNA (rRNA)
87
An RNA molecule with catalytic activity.
ribozyme
88
Enzyme that catalyzes the synthesis of an RNA molecule from a DNA template using ribonucleoside triphosphate precursors.
RNA polymerase
89
RNA molecules containing on the order of 200 nucleotides that participate in RNA splicing.
small nuclear RNA (snRNA)
90
Process in which intron sequences are excised from RNA molecules in the nucleus during the formation of a mature messenger RNA.
RNA splicing
91
Large assembly of RNA and protein molecules that splices introns out of pre-mRNA in the nucleus of eukaryotic cells.
spliceosome
92
Small RNA molecule that serves as an adaptor that "reads" a codon in mRNA and serves as the source of the amino acid added to the growing polypeptide chain.
transfer RNA (tRNA)
93
Small protein that can be covalently attached to other proteins; a major role is to mark target proteins for degradation by the proteasome.
ubiquitin
94
Process by which a pluripotent cell undergoes a progressive, coordinated change to a more specialized cell type, brought about by large-scale changes in gene expression.
differentiation
95
The enzymatic addition of methyl groups to cytosine bases in DNA; this covalent modification generally turns off genes by attracting proteins that block gene expression.
DNA methylation
96
Somatic cell that has been reprogrammed to resemble and behave like a pluripotent embryonic stem (ES) cell through the artificial introduction of a set of genes encoding particular transcription regulators.
induced pluripotent stem (iPS) cell
97
Small noncoding RNA that controls gene expression by base-pairing with a specific mRNA to regulate its stability and its translation.
microRNA (miRNA)
98
Short length of RNA produced from double-stranded RNA during the process of RNA interference. It base-pairs with complementary sequences in other RNAs, leading to the inactivation or destruction of the target RNA.
small interfering RNA (siRNA)
99
Having both hydrophobic and hydrophilic regions, as in a phospholipid or a detergent molecule.
amphipathic
100
Pigmented protein found in abundance in the plasma membrane of the salt-loving archaeon Halobacterium halobium; pumps protons out of the cell, fueled by light energy.
bacteriorhodopsin
101
Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells, it is rich in actin filaments that govern cell shape and drive cell movement.
cell cortex
102
Short, rigid lipid molecule present in large amounts in the plasma membranes of animal cells, where it makes the lipid bilayer less flexible.
cholesterol
103
Protective layer of carbohydrates on the outside surface of the plasma membrane formed by the sugar residues of membrane glycoproteins, proteoglycans, and glycolipids.
glycocalyx
104
Common phospholipid present in abundance in most cell membranes; uses choline attached to a phosphate as its head group.
phosphatidylcholine
105
Describes an organic molecule that contains a full complement of hydrogen; in other words, no double or triple carbon-carbon bonds.
saturated
106
Describes an organic molecule that contains one or more double or triple bonds between is carbon atoms.
unsaturated
107
Cell junction that helps hold together epithelial cells in a sheet of epithelium; actin filaments inside the cell attach to its cytoplasmic face.
adherens junction
108
Thin mat of extracellular matrix, secreted by epithelial cells, upon which these cells sit.
basal lamina
109
A member of a family of Ca2+-dependent proteins that mediates the attachment of one cell to another in animal tissues.
cadherin
110
Long, thin polysaccharide fiber that helps strengthen plant cell walls.
cellulose microfibril
111
Triple-stranded, fibrous protein that is a major component of the extracellular matrix and connective tissues; it is an abundant main protein in animal tissues, and different forms can be found in skin, tendon, bone, cartilage, and blood vessels.
collagen
112
An undifferentiated cell type derived from the inner cell mass of an early mammalian embryo and capable of differentiating to give rise to any of the specialized cell types in the adult body.
embryonic stem (ES) cell
113
Sheet of cells covering an external surface or lining an internal body cavity.
epithelium
114
Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells. A structural component of tissues that also influences their development and physiology.
extracellular matrix
115
Cell type that produces the collagen-rich extracellular matrix in connective tissues such as skin and tendon. Proliferates readily in wounded tissue and in tissue culture.
fibroblast
116
Extracellular matrix protein that helps cells attach to the matrix by acting as a "linker" that binds to a cell-surface integrin molecule on one end and to a matrix component, such as collagen, on the other.
fibronectin
117
In animal tissues, specialized connection between juxtaposed cells through which ions and small molecules can pass from one cell to another.
gap junction
118
Polysaccharide chain that can form a gel that acts as a "space filler" in the extracellular matrix of connective tissues; helps animal tissues resist compression.
glycosaminoglycan (GAG)
119
Structure that anchors epithelial cells to the basal lamina beneath them.
hemidesmosome
120
One of a family of transmembrane proteins present on cell surfaces that enable cells to make a break attachments to the extracellular matrix, helping them to crawl through a tissue.
integrin
121
The spread of cancer cells from the initial site of the tumor to form secondary tumors at other sites in the body.
metastasis
122
A gene that, when activated, can potentially make a cell cancerous. Typically a mutant form of a normal gene (proto-oncogene) involved in the control of cell growth or division.
oncogene
123
Cell-cell junction that connects one plant cell to the next; consists of a channel of cytoplasm lines by membrane.
plasmodesmata
124
Capable of giving rise to any type of cell or tissue.
pluripotent
125
Molecule consisting of one or more glycosaminoglycan chains attached to a core protein; these aggregates can form gels that regulate the passage of molecules through the extracellular medium and guide cell migration.
proteoglycan
126
Gene that when mutated or overexpressed can help transform a normal cell into a cancerous one.
proto-oncogene
127
Cell-cell junction that seals adjacent epithelial cells together, preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other.
tight junction
128
Member of a family of extracellular signal molecules that regulates cell proliferation and migration during embryonic development and that helps to maintain stem cells in a proliferative state.
Wnt protein
129
Mechanism by which a cell "eats itself," digesting molecules and organelles that are damaged or obsolete.
autophagy
130
Protein that makes up the coat of a type of transport vesicle that buds from either the Golgi apparatus (on the outward secretory pathway) or from the plasma membrane (on the inward endocytic pathway).
clathrin
131
Process by which cells take in materials through an invagination of the plasma membrane, which surrounds the ingested material in a membrane-enclosed vesicle.
endocytosis
132
Membrane-enclosed compartment of a eukaryotic cell through which material ingested by endocytosis passes on its way to lysosomes.
endosome
133
Process by which most molecules are secreted from a eukaryotic cell. These molecules are packaged in membrane-enclosed vesicles that fuse with the plasma membrane, releasing their contents to the outside.
exocytosis
134
Double membrane surrounding the nucleus. Consists of outer and inner membranes, perforated by nuclear pores.
nuclear envelope
135
Channel through which secreted large molecules move between the nucleus and the cytoplasm.
nuclear pore
136
Small membrane-enclosed organelle that contains enzymes that degrade lipids and destroy toxins.
peroxisome
137
A cell such as a macrophage or neutrophil that is specialized to take up particles and microorganisms by phagocytosis.
phagocytic cell
138
The process by which particulate material is engulfed by a cell. Prominent in predatory cells and in cells of the vertebrate immune system, such as macrophages.
phagocytosis
139
Type of endocytosis in which soluble materials are taken up from the environment and incorporated into vesicles for digestion.
pinocytosis
140
One of a family of small GTP-binding proteins present on the surfaces of transport vesicles and organelles that serves as a molecular marker to help ensure that transport vesicles fuse only with the correct membrane.
Rab protein
141
Region of the endoplasmic reticulum associated with ribosomes and involved in the synthesis of secreted and membrane-bound proteins.
rough endoplasmic reticulum
142
Enzyme that catalyzes the formation of cyclic AMP from ATP; an important component in some intracellular signaling pathways.
adenylyl cyclase
143
Enzyme that phosphorylates target proteins in response to an increase in Ca2+ ion concentration through its interaction with the Ca2+-binding protein calmodulin.
CaM-kinase
144
Small Ca2+-binding protein that modifies the activity of many target proteins in response to changes in Ca2+ concentration.
calmodulin
145
Small intracellular signaling molecule generated from ATP in response to hormonal stimulation of cell-surface receptors.
cyclic AMP
146
Small messenger molecule produced by the cleavage of membrane inositol phospholipids in response to extracellular signals. Helps activate protein kinase C.
diacylglycerol (DAG)
147
A membrane-bound GTP-binding protein involved in intracellular signaling; composed of three subunits, this intermediary is usually activated by the binding of a hormone or other ligand to a transmembrane receptor.
G protein
148
Intracellular signaling protein whose activity is determined by its association with either GTP or GDP. Includes both trimeric G proteins and monomeric GTPases, such as Ras.
GTP-binding protein
149
Extracellular signal molecule that is secreted and transported via the bloodstream (in animals) or the sap (in plants) to target tissues on which it exerts a specific effect.
hormone
150
Minor lipid component of plasma membranes that plays a part in signal transduction in eukaryotic cells; cleavage yields two small messenger molecules, IP3 and diacylglycerol.
inositol phospholipid
151
Small intracellular signaling molecule that triggers the release of Ca2+ from the endoplasmic reticulum into the cytosol; produced when a signal molecule activates a membrane-bound protein called phospholipase C.
inositol 1,4,5-triphosphate (IP3)
152
Mitogen-activated protein kinase. Signaling molecule that is the final kinase in a three-kinase sequence called the MAP-kinase signaling molecule.
MAP kinase
153
Set of three functionally interlinked protein kinases that allows cells to respond to extracellular signal molecules that stimulate proliferation; includes a mitogen-activated protein kinase (MAP kinase), a MAP kinase kinase, and a MAP kinase kinase kinase.
MAP-kinase signaling module
154
Intracellular signaling protein that toggles between an active and inactive state in response to receiving a signal.
molecular switch
155
Small, single-subunit GTP-binding protein. Proteins of this family, such as Ras and Rho, are part of many different signaling pathways.
monomeric GTPase
156
Locally acting gaseous signal molecule that diffuses across cell membranes to affect the activity of intracellular proteins.
nitric oxide (NO)
157
Protein inside a eukaryotic cell that, on binding to a signal molecule, enters the nucleus and regulates transcription.
nuclear receptor
158
Enzyme that phosphorylates inositol phospholipids in the plasma membrane, generating docking sites for intracellular signaling proteins that promote cell growth and survival.
phosphoinositide 3-kinase (PI 3-kinase)
159
Enzyme associated with the plasma membrane that generates two small messenger molecules in response to activation.
phospholipase C
160
Enzyme that catalyzes the transfer of a phosphate group from ATP to a specific amino acid side chain on a target protein.
protein kinase
161
Enzyme that phosphorylates target proteins in response to a rise in diacylglycerol and Ca2+ ions.
protein kinase C (PKC)
162
Enzyme that catalyzes the removal of a phosphate group from a protein, often with high specificity for the phosphorylated site.
protein phosphatase
163
One of a large family of small GTP-binding proteins that helps relay signals from cell-surface receptors to the nucleus. Many human cancers contain an overactive mutant form of the protein.
Ras
164
Enzyme-coupled receptor that phosphorylates target proteins on serine or threonine.
receptor serine/threonine kinase
165
Enzyme-couple receptor in which the intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to the receptor's extracellular domain.
receptor tyrosine kinase (RTK)
166
Enzyme that phosphorylates target proteins on serines or threonines.
serine/threonine kinase
167
Conversion of an impulse or stimulus from one physical or chemical form to another. In cell biology, the process by which a cell responds to an extracellular signal.
signal transduction
168
Hydrophobic signal molecule related to cholesterol; can pass through the plasma membrane to interact with intracellular receptors that affect gene expression in the target cell. Examples include estrogen and testosterone.
steroid hormone
169
Enzyme that phosphorylates target proteins on tyrosines.
tyrosine kinase
170
Traveling wave of electrical excitation caused by rapid, transient, self-propagating depolarization of the plasma membrane in a neuron or other excitable cell; also called a nerve impulse.
action potential
171
The movement of a solute across a membrane against its electrochemical gradient; requires an input of energy, such as that provided by ATP hydrolysis.
active transport
172
Type of couple transporter that transfers two different ions or small molecules across a membrane in opposite directions, either simultaneously or in sequence.
antiport
173
Channel that facilitates the transport of water, but not ions, across cell membranes; those found in the plasma membrane greatly increase a cell's permeability to water.
aquaporin
174
Long, thin extension that conducts electrical signals away from a nerve cell body toward remote target cells.
axon
175
An active transporter that uses energy supplied by ATP hydrolysis to actively expel Ca2+ from the cell cytosol.
Ca2+ pump (or Ca 2+ ATPase)
176
A protein that forms a hydrophilic pore across a membrane, through which selected small molecules or ions can passively diffuse.
channel
177
Short, branching structure that extends from the surface of a nerve cell and receives signals from other neurons.
dendrite
178
A shift in the membrane potential, making it less negative on the inside of the cell.
depolarization
179
Driving force that determines which way an ion will move across a membrane; consists of the combined influence of the ion's concentration gradient and the membrane potential.
electrochemical gradient
180
A protein or protein complex that uses energy supplied by ATP hydrolysis, an ion gradient, or light to actively move protons across a membrane.
H+ pump
181
Ion channel permeable to K+ that randomly flickers between an open and closed state; largely responsible for the resting membrane potential in animal cells.
K+ leak channel
182
An ion channel that is stimulated to open by the binding of a small molecule such as a neurotransmitter.
ligand-gated channel
183
An ion channel that allows the passage of select ions across a membrane in response to a physical perturbation.
mechanically gated channel
184
Voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other.
membrane potential.
185
Any transmembrane protein that provides a passageway for the movement of select substances across a cell membrane.
membrane transport protein
186
Transporter found in the plasma membrane of most animal cells that actively pumps Na+ out of the cell and K+ in using the energy derived from ATP hydrolysis.
Na+ pump
187
Passive movement of water across a cell membrane from a region where the concentration of water is high to a region where the concentration of water is low.
osmosis
188
The spontaneous movement of a solute down its concentration gradient across a cell membrane via a membrane transport protein, such as channel or a transporter.
passive transport
189
Transporter that uses a source of energy, such as ATP hydrolysis or sunlight, to actively move a solute across a membrane against its electrochemical gradient.
pump
190
Voltage difference across the plasma membrane when a cell is not stimulated.
resting membrane potential
191
Part of an ion channel that determines which ions the channel can transport; located in the region where the channel is narrowest.
selectivity filter
192
A transporter that transfers two different solutes across a membrane in the same direction.
symport
193
Transmembrane receptor protein or protein complex that opens in response to the binding of a neurotransmitter, allowing the passage of a specific inorganic ion; its activation can trigger an action potential in a postsynaptic cell.
transmitter-gated ion channel
194
Membrane transport protein that moves a solute across a cell membrane by undergoing a series of conformational changes.
transporter
195
Channel protein that permits the passage of selected ions, such as Na+, across a membrane in response to changes in the membrane potential. Found primarily in electrically excitable cells such as nerve and muscle cells.
voltage-gated channel
196
Protein in the plasma membrane of electrically excitable cells that opens in response to membrane depolarization, allowing Na+ to enter the cell. It is responsible for action potentials in these cells.
voltage-gated Na+ channel
BIO 203W
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