Quiz 10/18/14 Flashcards
Those mechanisms that depend directly on substrate-enzyme interactions are termed substrate-level regulation.
pH, inhibitors, temp
is from a Greek word meaning “another shape (or state)”
allosteric
enzymes regulated allostericly exist in ___ different shapes.
2
in one form the enzyme has a ____ affinity for substrate….___ reaction rate
high, high
in the other form the enzyme has ___ or ___ affinity for the substrate…. now rate.
little, no
Which form the enzyme takes on is determined by the presence and binding of appropriate regulatory substances termed _______ ____
allosteric effectors.
What size are allosteric effectors usually?
small
What do allosteric effectors usually regulate
enzymes for which they are neither a substrate nor an immediate product.
what causes a reversible alteration in the enzymes conformation
allosteric effector binding
In addition to an active site many enzymes have an ______,
allosteric site
where are the allosteric site located ______
allosteric domain
______ is where effectors can bind and alter the shape of the enzyme.
allosteric domeains
some allosteric effectors increase enzyme function when they bind.
allosteric activator
Other effectors inhibit the enzyme’s function when they bind.
allosteric inhibitor
What is the first step in the glycolytic pathway
phoshorylation of glucose-6-phosphate (G-6-P)
Almost invariably, enzymes at first or early steps of a multi-step pathway are regulated _____
allosterically
what reduces the rate of the first step effectively controls the whole pathway
feedback inhibition
what includes anabolic and catabolic pathways
feedback inhibition
feedback inhibitiors that do not resemble substrate
feedback inhibition
Enzymes composed of multiple subunits do not exhibit typical M and M kinetics.
the property of cooperativity
multimeric proteins often have multiple substrate binding sites
the property of cooperativity
as each site on the enzyme becomes successively occupied, the affinity at remaining sites changes
the property of cooperativity
in the property of cooperativity their are _______ sites on _____ subunits, the effect of substrate inding at one site is transmitted to other unfilled sites by enzyme conformational changes.
multiples, separate
in the property of cooperativity an M and M plot, an allosteric enzyme exhibiting cooperative interactions shows a _____ curve instead of a usual ______ one
sigmoidal, hyperbolic
binding at one site increases the affinity for substrate at other sites
positive cooperativity
binding at one site reduces the affinity for the substrate at other sites
negative cooperativity
positive cooperativiety binding at one site _____ the affinity for substrate at other sites
increases
negative cooperativity binding at one site _____ the affinity for the substrate at other sites
reduces
In this form of regulation, the activity of an enzyme is affected by the addition or removal of specific functional groups.
covalent modification
what are some of the specific functional groups that can be added or removed using covalent modification
phosphate groups, methyl groups, acetyl groups
Can covalent modification can be either _____ or ______. Either way, they act to raise or lower the activity of the enzyme.
reversible or irreversible
________ is probably the best unerstood covalent modification.
phosphorylation/dephosphorylation
reversible addition of phosphate groups are called
phosphorylation or dephosphorylation
phosphorylation or dephosphorylation most often involves the transfer of the phosphate groups from ATP to the hydroxyl group of a _________ in the protein.
serine, threonine, or tyrosine
Enzymes that catalyze the phosphorylation of other molecules
kinases aka phosphorylases
enzymes that catalyze the process of removing a phosphate, i.e. catalyze dephosphorylation
phosphoprotein phosphotases
The breakdown of glycogen in skeletal muscle cells is catalyzed by ___ ____.
Glycogen Phosphorylase
how is glycogen phosphorylase kinased?
the conformational change from inactvie b form to active a form is accomplished when the inactive b form itself becomes phosphorylated by the addition of a phosphate group to a particular serine on each of the 2 subunits of the phosphoylase b molecule
what is glycogen phosphorylase kinased?
phosphorylase kinase
in addition to regulation by its phosphorylation state, glycogen phosphorylase is also ______ regulated
allostericly
Glycogen Phosphorylase is inhibited by glucose and ____, but it is activated by ____
ATP, AMP
Glycogen Phosphorylase is used in a muscle cell which already has an adequate glucose supply, active phosphorylase a can not function due to _______ allosterically inhibiting the enzyme.
glucose
When a cell receives a hormonal signal it may trigger production of an allosteric effector, such as ______
cAMP (cylclic AMP)
This messenger molecule cAMP functions as an ______ _____ of a many enzymes, including a cytosolic protein kinase
allosteric activator
When phosphorylated, this cytosolic protein kinase catalyzes phosphorylation of many substrates, including _____
Phosphorylase Kinase.
Active _____ ___ will phosphorylate the enzyme discussed above, _____ ____ _
phosphorylase kinase, glycogen phosphylase b
one of the primary functions of sER was _____ ___
carbohydrate metabolism
_____ liberated from glycogen into the cytoplasm of liver cells are quickly isomerized into G6P which is then dephosphorylated by an sER specific membrane bound enzyme.
Glucose monomers (GIP)
In contrast, the enzyme _____ ___ which adds glucose units onto glycogen, responds in the opposite manner: inactive in the phosphorylated form and activated by dephosphorylation.
Glycogen Synthase
In addition to regulation by phosphorylation Glycogen Phosphorylase is also an _____ ____
allosteric enzyme
Glycogen Synthase is inhibited by _____ and ___, but it is activated by AMP.
glucose, ATP
So many enzymes are regulated by ______ _____ mechanisms.
multiple regulatory
multiple regulatory mechanisms allow the cell to respond ___ under a variety of _____ situations.
appropriately, different
What allows the cell to fine tune its response to multiple signals
multiple regulatory mechanisms
This type of activation involves the one-time, irreversible removal of a portion of the polypeptide chain by an appropriate proteolytic (protein-degrading) enzyme.
proteolytic cleavage
Proteolytic Cleavage modification is especially well demonstrated in these proteases
pepsin, trypsin, chymotrypsin, carboxypeptidase
Each of these is produced in an inactive form termed a ______ or _____. they must have a portion of their polypeptide removed to become active.
zymogen or proenzyme
inactive zymogens have modified names…… pro-whatever or whatever-ogen
pepsinogen, trysinogen, chymotrypsinogen, procarboxypeptidase
Why is it not prudent to synthesize these enzymes in their functional form?
inactive pepsinogen is secreted into the duodenum of the stomach in response to hormonal signals.
The latter are proteolyticly activated initially by an ______ secreted by duodenal cells
enterokinase
activated zymogens ____ almost all our ingested proteins into free amino acids, which are absorbed by the intestinal epithelium cells
digest
_____ is synthesized in the pancrease as ______. When it reaches the small intestine it is activated by the removal of a hexapeptide from its N-terminus by an enterokinase or by cathepsin B, a lysosomal enzyme present in acinar cells.
Trypsin, trypsinogen
What is an indicator of the First Molecular Event during experimental Pancreatitis
TAP (trypsin Activation Protein)
