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Definition
channels that perforate cell walls and connect cells
unify plant cells into a continuum (most cells), cells share cytosol |
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| types of cell junctions in animal tissues (3) |
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Definition
| tight junctions, desmosomes, gap junctions |
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Definition
| plasma membranes of neighboring cells are pressed tightly against each other and bound together by proteins, prevent fluid from moving across a layer of cells |
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Definition
"rivets" that fasten cells together into sheets
ex. hold muscle cells together |
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Definition
cytoplasmic channels from one cell to another, similar to plasmodesmata
consist of membrane proteins that surround a pore
ions, sugars, amino acids, and other small molecules can pass |
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Term
| 3 stages of cell signalling |
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Definition
reception
transduction
response |
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Term
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Definition
transmembrane receptor that works with a G protein, a protein that binds GTP or GDP
G protein is inactive when bound to GDP
when a signaling molecule binds to GPCR, the receptor is activated and the cytoplasmic side binds inactive G protein, displacing GDP. This activates the G protein.
Activated G protein dissociates from the receptor, diffuses along the membrane, then binds to an enzyme, altering the enzyme's activity. |
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Definition
binds GTP
functions as a GTPase - hydrolyzes bound GTP to GDP, returning it to its inactive state where it is available for reuse |
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Definition
receptor tyrosine kinases
can trigger many pathways at once
before signaling molecule binds, two receptors are separate
each receptor has a ligand-binding site, an alpha helix spanning the membrane, and an intracellular tail containing tyrosines
binding of a signaling molecule causes monomers to form a dimer
dimerization activates the tyrosine kinase region of each monomer; each tyrosine kinase adds a P from an ATP to a tyrosine on the tail of the other monomer in the dimer
the receptor is activated, and is recognized by relay proteins inside the cell
each activated protein can trigger a different transduction pathway
malfunction is associated with many cancers (ex. HER2 is a type of RTK) |
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Definition
| enzyme that catalyzes transfer of phosphate groups |
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Definition
| catalyzes transfer of a phosphate group from ATP to tyrosine on a substrate protein |
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Definition
membrane receptor containing a "gate"
when a signaling molecule binds, the gate opens or closes, allowing Calcium and sodium, for example, through a channel in the receptor
very important in the nervous system -> neurotransmitters bind as ligands to ion channels on the receiving cell, causing the channels to open. ions flow in or out, triggering an electrical signal that propagates down the length of the receiving cell |
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Term
| intracellular receptor proteins |
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Definition
| found either in cytoplasm or nucleus of target cells |
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Definition
secreted by the adrenal gland, travels through the blood, and enters cells all over the body
response only occurs in kidney cells, which contain a receptor molecule for aldosterone
controls water and sodium flow in kidney cells
acts as a transcription factor that turns on specific genes |
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Term
| cytoplasmic protein kinases |
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Definition
| phosphorylate serine or threonine, not tyrosine |
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Term
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Definition
| a series of proteins are phosphorylated, each protein adding a phosphate group to the next protein, activating the next protein in the cascade |
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Term
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Definition
enzymes that can rapidly remove phosphate groups from proteins
turn off signal transduction pathway when the initial signal is no longer present
make protein kinases available for reuse |
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Definition
| not all components of signal transduction are proteins; second messengers are small, water-soluble molecules or ions that can readily spread throughout the cell through diffusion |
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Definition
synthesized by adenylyl cyclase
can boost normal concentration quickly
broadcasts the signal to the cytoplasm
(converted back to AMP by phosphodiesterase) |
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Term
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Definition
| converts ATP to cAMP in response to an extracellular signal (epinephrine) |
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Term
| inositol triphosphate (IP3) |
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Definition
| releases calcium from the ER |
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Definition
| relay proteins to which other relay proteins are simultaneously attached; enhances speed and accuracy of signal transfer |
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Term
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Definition
| cellular agens chop up DNA and fragment the organelles and other cytoplasmic components, cell shrinks and becomes lobed, the cells parts are packaged up in vesicles that are engulfed and digested by specialized scavenger cells. protects neighboring cells form damage that they would suffer if dying cells leaked out their contents, including digestive enzymes. |
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Definition
| the main proteases of apoptosis |
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Term
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Definition
| functions in mitochondrial electron transport in healthy cells but acts as a cell death factor when released from mitochondria |
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Term
| apoptosis signal outside of cell |
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Definition
| when a death signaling ligand occupies a cell surface receptor, leads to activation of caspases and other enzymes that carry out apoptosis, without involving mitochondrial pathway |
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Term
| apoptosis signal from inside cell |
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Definition
signal can come from nucleus, generated when DNA has suffered irreparable damage
signal can come from ER, when excessive protein misfiling occurs |
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Definition
| protein complexes that attach sister chromatids |
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Definition
| region of chromosomal DNA where the chromotid is attached most closely to its sister chromatid |
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Definition
| includes mitosis and cytokinesis, alternates with interphase |
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Definition
divided into G1 phase (first gap), S phase (synthesis), G2 phase (second gap)
during all three sub phases, the cell grows by producing proteins and cytoplasmic organelles such as mitochondria and ER |
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Definition
| duplication of chromosomes |
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Definition
| fibers made of microtubules |
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Term
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Definition
nuclear envelope encloses the nucleus
nucleus contains one or more nucleoli
two centrosomes have formed by duplication of a single centrosome, centrosomes organize microtubules of the mitotic spindle
chromosomes can't be seen individually (have not condensed yet) |
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Term
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Definition
chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope
nucleoli disappear
each duplicated chromosome appears as two sister chromatids joined at their centromeres
mitotic spindle begins to form
centrosomes move away from each other, propelled by the lengthening of the microtubules between them |
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Term
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Definition
composed of centrosomes and microtubules
radial arrays of shorter microtubules that extend from the centrosomes are call asters |
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Term
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Definition
| radial arrays of shorter microtubules that extend from the centrosomes |
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Term
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Definition
nuclear envelope fragments
microtubules extending from each centrosome invade nuclear area
chromosomes even more condensed
each of the chromatids now has a kinetochore, a specialized protein structure at the centromere
some of the microtubules attach to kinetochores
nonkinetochore microtubules interact with those from the opposite pole of the spindle |
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Term
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Definition
the centrosomes are now at opposite poles of the cell
the chromosomes arrive at the metaphase plate
kinetochores of the sister chromatids are attached to kinetochore microtubules coming from opposite poles |
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Term
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Definition
cohesin proteins are cleaved
kinetochore microtubules shorten and sister chromatids move towards the centromere region
cell elongates as nonkinethochore microtubules lengthen
by the end, two cells have equivalent and complete collections of chromosomes |
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Term
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Definition
daughter nuclei form in the cell
nuclear envelopes arise from the fragments of the paren cell's nuclear envelope and other portions of the endomembrane system
nucleoli reappear
microtubules depolymerized
mitosis is complete |
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Term
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Definition
| in animal cells, involves formation of cleavage furrow |
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Term
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Definition
a shallow groove in the cell surface near the old metaphase plate
on the cytoplasmic side of the furrow is a contractile ring of acting microfilaments associated with myosin, which cause the ring to contract |
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Term
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Definition
no cleavage furrow
vesicles derived from golgi move along microtubules to the middle of the cell, where they coalesce, producing a cell plate
cell wall materials carried in the vesicles collect inside the plate cell as it grows
the cell plate enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell, resulting in two daughter cells |
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Term
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Definition
| prokaryotes grow in size and split in half |
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Definition
a protein that cyclically fluctuates the its concentration in the cell
binds to kinases that regulate cell cycle, activating them
cyclin levels rise during S and G2 phases and drop off during M phase |
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Term
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Definition
| activity rises and falls with changes in cyclin |
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Term
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Definition
cyclin-cdk complex = maturation promoting factor
triggers cell passage into M phase, past G2 checkpoint
phosphorylates a variety of proteins, initiating mitosis
helps switch itself off by initiating a process that leads to destruction of its own cyclin |
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Term
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Definition
if a cell passes the G1 checkpoint, it usually divides
if it doesn't, it may exit the cycle and enter G0 = non dividing state
most cells in the body are in G0 |
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Term
| alternation of generations |
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Definition
| plants and some algae have a diploid and haploid stage of their lifecycle |
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Term
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Definition
muticellular diploid stage in alternation of generations
meiosis in the sporophyte produces haploid cells called spores
spores dont fuse with another cell but divide mitotically, generating the gametophyte |
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Term
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Definition
muticellular haploid phase generated from spores
create gametes through mitosis
fusion of two haploid gametes at fertilization result in a diploid zygote, which develops into the next sporophyte generation |
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