exam 3 Flashcards
in order for multicellular organisms to communicate you need _______ cell and a _______ cell
signaling
target
target cells need _____ proteins to detect the signal
receptor
the extracellular signal is converted into a intracellular signal, which is a process known as ____________
transduction
_______ has a variety of functions, depending on the cell that receives the signal
acetylcholine
intracellular signal molecules generally influence transcription and bind to a member of the nuclear receptor ______________
superfamily
these relays involve ___________ signaling pathways, that can operate in the following ways
intracellular
_______ of these proteins is typically done by phosphorylation, while ______ is typically done by dephosphorylation
activation
deactivation
Many pathways involve several kinases activating the next kinase in the pathway, which activates the next kinase; these are referred to as phosphorylation ______
cascades
CPCRs span the plasma membrane back and forth ___ times
7
the α subunit has an affinity for ____ when it is ______
GDP
inactive
when a signal molecule binds to the GPCR, it causes the αsubunit to exchange the GDP for a _____ (it is now ________)
GTP
active
eventually, the α subunit will _______ its GTP to GDP, which will ‘turn off’ the system and restore the G protein to its inactive state
hydrolyze
the response of skeletal muscle to __________ is an excellent example of a cAMP pathway
adrenaline
________ filaments have a diameter between that of microtubules and actin
intermediate
the main purpose of these filaments is to provide _____ strength, which prevents the overstretching of cells
tensile
eight of these tetramer ropes come together to form a
single filament, which is made up of a total of __ subunits
32
Because of the α and β arrangements of the tubulin subunits, the microtubules have _____ (the α being the - negative end, and the β being the + positive end).
polarity
microtubules show _________ instability
dynamic
growing microtubules end up with a ‘GTP ____’
cap
__________ proteins can help anchor microtubules onto the plasma membrane
capping
______ proteins help direct movement in the cell
motor
they use the energy of ____ to drive their incremental movement along filaments
ATP
there are many other actin-binding proteins that help control the behavior of actin filaments, including capping proteins (prevent depolymerization) and ____________ proteins (provide a starting point for filament growth)
nucleating
“cell crawling” is mediated by _______ filaments, where the extending protrusions are driven by actin polymerization at the cell surface (i.e. the growth of actin filaments ‘pushes’ out a cellular protrusion)
actin
Common protrusions driven by actin are ______ (“false feet”) of amoebas
pseudopods
myosin involved in muscle contraction belongs to the ___________ subfamily
myosin-II
myosin-II molecules are _________ of myosin molecules, with each dimer having two heads and a rod-like tail
dimers
bundles of actin and myosin filaments can therefore generate a _____________ force seen in muscle cells
contractile
muscle fibers are made of several __________, which are composed of contractile units called ____________
myofibrils
sarcomeres
when a muscle cell is excited via T _________, Ca2+ is released from the sarcoplasmic reticulum (modified ER)
tubules
in the absence of Ca2+, a rod-shaped protein filament called ______________ blocks the actin/myosin binding sites, which prevents muscle contraction
tropomyosin
when Ca2+ is available, it binds to _____________, which in turn shifts the position of tropomyosin to expose the actin binding sites
troponin
the remaining three phases (G1, S and G2) together are referred to as ____________
interphase
the G phases are also times for important ___________
checkpoints
if the G1 conditions are not met, the cell enters into a specialized __________ phase known as G0, which can last for the lifetime of the cell in some cases
resting
__________ can arise from G1 misregulation - where cells divide without any checks and balances
cancer
studying the cell cycle control system has occurred with ________ primarily since the proteins involved are highly conserved in all eukaryotic organisms
yeast
proteins called ________ activate enzymes known as cyclin-dependent protein kinases (CDKs) by forming complexes
cyclins
cyclin-CDK is inactive until it is finally turned on by a _______________ (i.e. it is turned on by the loss of a -PO4)
phosphatase
the concentration of a cyclin depends on ___________
proteolysis
when cyclins reach a certain level, they are tagged with __________, which sends them to the proteasome
ubiquitin
at the end of M phase, the cell is split in two in a process known as ___________
cytokinesis
cleavage begins with a ____________ furrow (near the end of anaphase) perpendicular to the axis of the mitotic spindle
cleavage
variations in the position of the mitotic spindle can create ____________ division (important for embryogenesis)
asymmetric
a ______________ ring composed of actin and myosin filaments causes the contraction (the same proteins that allow muscle contraction)
contractile
a _________________ structure is formed, which attracts Golgi vesicles full of polysaccharides and glycoproteins (young cell wall components)
phragmoplast
___________ (“rebar” made of glucose strands) and _________ (polyphenolic “glue”) are added to complete the new cell wall
cellulose
lignin
programmed cell death is known as ________________
apoptosis
cells that die from injury is called ___________
necrosis
the cell surface is also changed to attract ________________, which engulf the cell before it bursts open
macrophages
during apoptosis, enzymes called ____________ initiate an irreversible pathway of cell death (once it starts it can’t be undone)
caspases
growth and division of cells of multicellular organisms rely on __________ proteins
signal
____________ factors act by binding to cell-surface receptors, which then regulate the Bcl2 family of proteins
survival
____________ act by cell-surface receptors, which initiate pathways that lead to release of “molecular brakes” that prevent cells from entering S phase from G1 phase
mitogens
well-known mitogen is platelet-derived growth factor(PDGF), which is released from ____________ at the site of a wound; PDGF then stimulates cell proliferation of surviving cells at the wound site, which leads to healing
platelets
when the liver is injured or wounded, _____________ growth factor helps to promote cell division among the surviving liver cells
hepatocyte
__________ factors operate through cell-surface receptors and stimulate pathways that lead to increased protein production and/or decreased protein degradation
growth
__________ is an example of signal proteins that prevent cell growth
myostatin
there are two main stages involved in generating chemical energy via membranes (called _______________ coupling)
chemiosmotic
with mitochondria, a single glucose molecule produces __ ATP
36
the _______ membrane contains transport proteins called ________ that allow relatively small molecules (5 kDa or less) to pass through easily
outer
porins
the ________ membrane is less permeable, and contains ATP synthase and the proteins required for the electron transport chain; it is also convoluted, forming infolds called ____________ that help to increase the surface area within the mitochondria
inner
cristae
the _________ is the large internal space of the mitochondria that is bordered by the inner membrane
matrix
the _______________ space is the space between the inner and outer membrane
intermembrane
the space contained by the inner membrane is called the _________
stroma
these enzymes are found in the _____________ membrane of disc-like sacs called thylakoids, that exist in stacks called ________
thylakoid
grana
chloroplasts contain multi-protein complexes called ________________ embedded in the thylakoid membrane
photosystems
the antenna complex contains hundreds of _______________ and other pigment molecules that are able to funnel energy toward the reaction center
chlorophyll
when a special chlorophyll molecule (_______) in the reaction center of photosystem II (PSII) is excited by energy from
P680
the electron is then replaced by the oxidative splitting (____________) of a water molecule, which also generates O2
photolysis
these protons are then pumped across the thylakoid membrane by ATP synthases, which generate ATP in the stroma in a process known as __________________________
photophosphorylation
The special chlorophyll (_______) of photosystem I (PSI) also absorbs light energy and loses an electron in the same way as photosystem II
P700
the ATP and NADPH produced from the light reactions are used for carbon __________
fixation
the most important enzyme in the Calvin cycle is ___________
Rubisco
breaking down compounds is referred to as _____________
catabolism
______________ (“sugar splitting”) occurs in the cytoplasm of cells and does not require oxygen
glycolysis
for each glucose consumed, two ATP are consumed and four are produced - resulting in a net gain of _ ATP
2
his production of ATP without the mitochondria is known as ___________-level phosphorylation
substrate
after glycolysis, pyruvate enters the _______________ where it is converted to acetyl CoA
mitochondria
a process called _____________ involves the production of more complex molecules from simple ones
anabolism
notice how glycolysis and the citric acid cycle are central to ___________________
metabolism
what are the 2 processes that use actin and myosin to generate a contractile force
Muscle contraction
Cytokinesis
What are the different strategies between a plant and animal cell for cytokinesis?
plant walls are rigid whereas animal cells are squishy
What is the difference between apoptosis and necrosis?
Apoptosis is a planned and organized cell death
Necrosis is a unplanned and messy cell death
what are the 2 main types of receptors?
cell-surface receptors
intracellular receptors
What are the 2 common enzymes targeted by G-protein subunits?
Adenylyl cyclase
Phospholipase C
What are the 2 main types of motor proteins that move along microtubules?
Kinesins (move away from the organizing center) toward positive end
Dynein’s (move toward the organizing center) toward the negative end
Give 2 ways actin and microtubules are similar
both have polarity
both made of subunits
Give 2 ways actin and microtubules are different
microtubules are hollow actin is not hollow
actin uses ATP to grow microtubules use GTP to grow
What are 2 ways mitochondria and chloroplasts are the same
Both have inner membrane
Both have outer membrane
What are 2 ways mitochondria and chloroplasts are different
Chloroplasts have 3 membranes while mitochondria only have 2
Chloroplast membranes are much larger than mitochondria
What are the 3 main types of phosphorylation
Oxidative
Photo phosphorylation
substrate level
