AP Biology Unit 4: Cell Communication and Cell Cycle Key Terms

apoptosis

programmed cell death

autocrine signal

signal that is sent and received by the same or similar nearby cells

autoinducer

signaling molecule secreted by bacteria to communicate with other bacteria of its kind and others

cell-surface receptor

cell-surface protein that transmits a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell

chemical synapse

small space between axon terminals and dendrites of nerve cells where neurotransmitters function

cyclic AMP (cAMP)

second messenger that is derived from ATP

cyclic AMP-dependent kinase

(also, protein kinase A, or PKA) kinase that is activated by binding to cAMP

diacylglycerol (DAG)

cleavage product of PIP2 that is used for signaling within the plasma membrane

dimer

chemical compound formed when two molecules join together

dimerization

(of receptor proteins) interaction of two receptor proteins to form a functional complex called a dimer

endocrine cell

cell that releases ligands involved in endocrine signaling (hormones)

endocrine signal

long-distance signal that is delivered by ligands (hormones) traveling through an organisms circulatory system from the signaling cell to the target cell

enzyme-linked receptor

cell-surface receptor with intracellular domains that are associated with membrane-bound enzymes

extracellular domain

region of a cell-surface receptor that is located on the cell surface

G-protein-linked receptor

cell-surface receptor that activates membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components

growth factor

ligand that binds to cell-surface receptors and stimulates cell growth

inhibitor

molecule that binds to a protein (usually an enzyme) and keeps it from functioning

inositol phospholipid

lipid present at small concentrations in the plasma membrane that is converted into a second messenger; it has inositol (a carbohydrate) as its hydrophilic head group

inositol triphosphate (IP3)

cleavage product of PIP2 that is used for signaling within the cell

intercellular signaling

communication between cells

internal receptor

(also, intracellular receptor) receptor protein that is located in the cytosol of a cell and binds to ligands that pass through the plasma membrane

intracellular mediator

(also, second messenger) small molecule that transmits signals within a cell

intracellular signaling

communication within cells

ion channel-linked receptor

cell-surface receptor that forms a plasma membrane channel, which opens when a ligand binds to the extracellular domain (ligand-gated channels)

kinase

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule.

ligand

molecule produced by a signaling cell that binds with a specific receptor, delivering a signal in the process

mating factor

signaling molecule secreted by yeast cells to communicate to nearby yeast cells that they are available to mate and communicating their mating orientation

neurotransmitter

chemical ligand that carries a signal from one nerve cell to the next

paracrine signal

signal between nearby cells that is delivered by ligands traveling in the liquid medium in the space between the cells

phosphatase

enzyme that removes the phosphate group from a molecule that has been previously phosphorylated

phosphodiesterase

enzyme that degrades cAMP, producing AMP, to terminate signaling

quorum sensing

method of cellular communication used by bacteria that informs them of the abundance of similar (or different) bacteria in the environment

receptor

protein in or on a target cell that bind to ligands

second messenger

small, non-protein molecule that propagates a signal within the cell after activation of a receptor causes its release

signal integration

interaction of signals from two or more different cell-surface receptors that merge to activate the same response in the cell

signal transduction

propagation of the signal through the cytoplasm (and sometimes also the nucleus) of the cell

signaling cell

cell that releases signal molecules that allow communication with another cell

signaling pathway

(also signaling cascade) chain of events that occurs in the cytoplasm of the cell to propagate the signal from the plasma membrane to produce a response

synaptic signal

chemical signal (neurotransmitter) that travels between nerve cells

target cell

cell that has a receptor for a signal or ligand from a signaling cell

anaphase

the stage of mitosis during which sister chromatids are separated from each other

binary fission

prokaryotic cell division process

cell cycle

ordered series of events involving cell growth and cell division that produces two new daughter cells

cell cycle checkpoint

mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages

cell plate

a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate; will ultimately lead to formation of a cell wall to separate the two daughter cells

centriole

rod-like structure constructed of microtubules at the center of each animal cell centrosome

centromere

region at which sister chromatids are bound together; a constricted area in condensed chromosomes

chromatid

single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere

cleavage furrow

constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division

condensin

proteins that help sister chromatids coil during prophase

cyclin

one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle

cyclin-dependent kinase

one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation

cytokinesis

division of the cytoplasm following mitosis that forms two daughter cells.

diploid

cell, nucleus, or organism containing two sets of chromosomes (2n)

FtsZ

a tubulin-like protein component of the prokaryotic cytoskeleton that is important in prokaryotic cytokinesis (name origin: Filamenting temperature-sensitive mutant Z)

G0 phase

distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide

G1 phase

(also, first gap) first phase of interphase centered on cell growth during mitosis

G2 phase

(also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis

gamete

haploid reproductive cell or sex cell (sperm, pollen grain, or egg)

gene

physical and functional unit of heredity, a sequence of DNA that codes for a protein

genome

total genetic information of a cell or organism

haploid

cell, nucleus, or organism containing one set of chromosomes (n)

histone

one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes

homologous chromosomes

chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent

interphase

period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions)

karyokinesis

mitotic nuclear division

kinetochore

protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase

locus

position of a gene on a chromosome

metaphase

stage of mitosis during which chromosomes are aligned at the metaphase plate

metaphase plate

the equatorial plane midway between two poles of a cell where the chromosomes align during metaphase

mitosis

(also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase

mitotic phase

period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis

mitotic spindle

apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis

nucleosome

subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteins

oncogene

mutated version of a normal gene involved in the positive regulation of the cell cycle

origin

(also, ORI) region of the prokaryotic chromosome where replication begins (origin of replication)

p21

cell cycle regulatory protein that inhibits the cell cycle; its levels are controlled by p53

p53

cell cycle regulatory protein that regulates cell growth and monitors DNA damage; it halts the progression of the cell cycle in cases of DNA damage and may induce apoptosis

prometaphase

stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores

prophase

stage of mitosis during which chromosomes condense and the mitotic spindle begins to form

proto-oncogene

normal gene that when mutated becomes an oncogene

quiescent

refers to a cell that is performing normal cell functions and has not initiated preparations for cell division

Retinoblastoma protein (Rb)

regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F)

S phase

second, or synthesis, stage of interphase during which DNA replication occurs

septum

structure formed in a bacterial cell as a precursor to the separation of the cell into two daughter cells

telophase

stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelope

tumor suppressor gene

segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled division