BMSC 200 Final no pics Flashcards
difference between coenzymes and cofactors
coenzymes = organic (vitamins)
cofactors = inorganic (metalions)
describe the difference between the rate and the equilibrium of a reaction
the equilibrium is determined by the difference in free energy between the substrate and the product
the rate of the reaction is determined by the difference between the energy of the transition state and the substrate, enzymes can lower this influencing the rate of the reaction
however, an enzyme has no effect on the equilibrium of a reaction
what are the binding effects of an enzyme catalyst
substrate binding –> reduces entropy
aligns functional groups
desolves substrate ( removes water)
distorts substrate
induced fit
transition state stabilization
increased interaction between enzyme and substrate during transition state
active site is complimentary to TS
must be similar enough to substrate to ensure specificity but different enough to promote change
enzymes have higher affinities to TS than S
provides microenvironment
what are transition state analogs
stable compound resembling unstable transition state
type of competitive inhibitor
bind to active site w high affinity
Antibodies against transition state analogues may have catalytic activity.
what are the chemical effects of enzyme catalyst
acid base catalysis –>
uses his
catalytic proton transfer
covalent catalysis –>
covalent linkage to substrate
regenerates free enzyme
ex) sucrose phosphorylase
describe Michalis menton kinetics
describe relationship of substrate concentration and initial velocity
allosteric enzymes do not obey this
V0= vmax(S) / km+(S)
km = 1/2vmax
When [S] < Km, enzymes are highly sensitive to changes in substrate
concentration but have very little activity.
When [S] > Km, enzymes have high activity but are insensitive to
changes in substrate concentration.
When [S] = Km, enzyme has significant activity and is responsive to
changes in substrate concentration.
describe lineweaver burke plots
can find vmax and km
Comp –> Y axis same but X axis closer
increase Km
bind only free enzyme E
Vmax is same
Non Comp –> Y axis higher X axis same
decrease Vmax
bind to E and ES
Km same
Uncomp –> y and x both farther
decrease vmax
decrease Km
bind to only ES
discuss serine proteases
cleave polypep chains (peptide bonds)
diff proteases have diff specificity
example of both acid base and covalent catalysis
trypsin –> cleave pos (lys arg)
chymotrypsin –> cleave aromatics (phe met)
elastase –> cleaves small hydrophobic (gly ala)
what is the catalytic triad
His, H, acid base catalysis
aspartate, Asp, D, stabilization
Ser, S covalent catalysis
enzyme regulation
through covalent modification (phosphorylation)
non covalent –> allosteric regulation
uses negative feedback loops
one at end can regulate one at beginning, or first one of branch
if two join to form one, can regulate first of each branch
allosteric enzymes
usually quaternary structure
usually rate limiting step
do not obey Michalis mention kinetics instead have S curve
bind non covalently
have active R and inactive T (R ready to go)
activators bind to R, so can substrates but not T
more sensitive to changes in substrate concentration near Km then MM enzymes
this sensitivity is called the threshold effect (think back to r t states of hemoglobin, once one switches they all do
Describe phosphofructokinase 1
in glycolysis
PEP is heterotropic allosteric inhibitor
ADP is heterotropic allosteric activator
noncovalent modification
describe glycogen metabolism
covalent modification
glucose –> glycogen
glycogen synthase to form glycogen anabolic, when non phosphorylated/ insulin
glycogen phosphorylase to form glucose catabolic when phosphorylated/ hungry
how do you find the number of stereoisomers in a monosaccharide
2^n where n is number of chiral carbons
what are epimers
sugars that differ at only a single chiral center
what are the two ring structures cyclized sugars can form
pyran of pyranose 6 c
furan or furanose 5c (in the ring)
what is the anomeric carbon
carbon that becomes chiral as a result of cyclization
cyclization always involves either 1-5 or 2-5c
on 6c or pyran ring forms the anomeric carbon is C1 (ALDOSES)
on 5c or furan ring forms the anomeric carbon is on c2 (KETOSES)
how can you tell the alpha or beta forms of cyclized carbons
what is switching between the two called
beta on top
alpha on bottom
switching between the two is called mutarotation
describe the nomenclature of disaccharides
glycosidic bonds are the structural linkage
0-glycosisic occurs through oxygen
N glycosidic is on nitrogen or amide
monosaccharides involved
ring type
configurations
‘linkages
end chain with free anomeric carbon is reducing end
always name non reducing end first (osyl then ose)
describe the energy storage polysaccharides
in plants
starch (amylose, unbranched; amylopectin, branched)
has a1-6 branch every 25 residues
many non reducing ends
in animals
glycogen
has a a1-6 branch every 9 residues
even more non reducing ends
means animals can mobilize their energy faster than plants bc more branches
all use a1-4 linkages
all homopolysaccharides
describe the structural polysaccharides
cellulose (fiber in plant cells)
chitin
use B1-4 linkages instead
linear
fibrils formed from parallel long linear chains linked through hbonds
means they are rigid and cannot be broken easily by amylase
glycolipids
used in blood group antigens
difference between glycoproteins and proteoglycans
glycoproteins
more protein
variety of roles
either 0 or N linked
ex) EPO
Proteoglycans
more sugar (carb)
structural and lubricating
ex) glycosaminoglycans –> introduces negatively charged fibrous strands
