biochem Flashcards
amino acids are what
molecs with two functional groups - amino group (NH2) carboxyl group (COOH)
chiral centres mean what
four different groups attached to it (except glycine)
major sites of metabolic activity in body
liver, skeletal and cardiac muscles, brain, adipocytes
ahti-hypertensive medications are called what
ACE inhibitors
ACE does what
catalyzes reaction that converst peptide angiotensin I to angiotensin II
angiotensin II does what
directly causes constriction of blood vessels to raise blood pressure, and also stimulates release of hormon aldosterone
do catalysts impact the thermodynamics of a biological reaction?
no
equilibrium position doesn’t change
oxidoreductases
catalyze redox reactions
often have cofactor that acts as e- carrier such as NAD+ NADP+
reductant is electron ______
donor
oxidant is the electron ________
acceptor
transferases
catalyze movement of functional group from one molecule to another
kinases catalyze the transfer of a phosphate group, generally from ATP, to another molecule
hydrolases
catalyze breaking of compound into two molecules using the addition of water
phosphatase - cleaves phosphate group from another molecule
lysaes
catalyze cleaage of a single molecule into two products
do not requre water as a substrate and do not act as oxidoreductases
isomerase
catalyze rearrangement of bonds within a molecule
catalyze rxns between steroisomers as well as constitutional isomers
ligases
catalyze addition or synthesis reactions, generally between large similar molecules and often require ATP
remember nucleic acid synthesis and repair
endergonic rxn
requires nrg
exergonic rxn
nrg is given off
enzymes lower the activation energy of a reaction by what
stabilizing the transition state
lock and key theory
enzymes active site (lock) is already in appropriate conformation for substrate (key) to bind
induced fit
more scienifically accepted
stats with substrate and enyme active site that don’t seem to fit together but once subbstrate is present and ready to interact with active site, molecules find induced fit is comfy for both
apoenzyme
enzyme without its cofactor
holoenzyme
enzyme with necessary cofactor
tightly bound cofactors or coenzymes that are necessary for enzyme function
prosthetic groups
cofactors are generally __ molecs or________ ions, and coenzymes are small ______ groups
inorganic
metal
organic
the only way to increase vmax is to what
increase enzyme conc
michaelis menten equation is what
describes how the rate of the rxn depends on the conc of both the enyzyme and substrate which forms product
km is conc at what
1/2 the enzyme’s active sites are in use and the velocity of rxm is half of vmax
it is substrate concentration
michaelis constant
a low km is what and a high one is what
low high affinity for substrate
high is low affinity for enzyme
kcat is what
equilibrium constant for a rxn that is being catalyzed by an enzyme
ratio of kcat/km is what
catalytic efficiency of enzyme
higher catalytic efficiency is what
more efficient enzyme
lineweaver burk plot is a
double reciprocal graph of the michaelis menten equation
x axis of lineweaver burk is what
-1/km
intercept of the line with y axis in lineweaver burk is what
1/vmax
where is the lineweaver burk plot useful?
when determining the type of inhibition that an enzyme is experiencing bc vmax and km can be compared without estimation
cooperative enzymes
have multiple subunits and mutliple active sites
hill’s coefficient is what
mathematical representation of the cooperativeness of an enzyme
cooperative enzymes are subject to activation and inhibition, both________ and through______ sites
competitively
allosteric
if hills coefficient is:
> 1
<1
=1
positively cooperative binding is occuring - such that after one ligand is bound the affinity of the enzyme for further lingans increases
negatively cooperative bidning is occuring, such that after one ligand is bound the affinity of the enzyme for fruther ligands decreases
the enzyme does not exhibit cooperative binding
enzyme catalyzed rxns tend to double in velocity for every ____ increase in temp until optimum temp is reached
10 degrees celsius
pH affects the ___ of the active site, but also because changes in pH can lead to _ of the enzyme
ionization
denaturation
increasing levels of salt can disrupt what causing what
hydrogen and ionic bonds
causes partial change in the conformation of the enzyme and can cause denaturation
feed forward regulation
regulated by intermeiates that precede the enzyme in the pathway
competitive inhibition
how to overcome as well
involves occupancy of active site
can be overcome by adding more substrate so that the substrate to inhibitor ratio is higher
does adding a competitive inhibitor alter vmax?
no, because if enough substrate is added, it will outcompete the inhibitor and be able to run the reaction at maximum velocity
what does a competitive inhibitor increase
measured value of km - bc substrate concentration has to be higher to reah half the maximum velocity in the presence of the inhibitor
noncompetitive inhibitor
binds to allosteric site instead of active site, which induces a change in enzyme formation
cannot be overcome by adding more substraatewh
what does a noncompetitive inhibiotr do
decreases measured value of vmax becauee there is less enzyme avaiblable to react - it does not alter value of km bc any copies of enzyme that are still active maintain same affinity for their substrate
mixed inhibition
results when an inhibitor can bind to either the enzyme or the enzyme ubstrate complex, but has different affinity for each
bind at allosteric sites
what does mixed inhibition alter?
experimental value of km depending on prefernece of inhibitor for enzyme vs enzyme substrate complex
if mixed inhibitor preferentially binds to enzyme, it increases the __ value and lowers afiniity, if the inhibtor binds to the enzyme substrate comple, it ____ the km value and increases finity . in either case, ___ is decreased
km
lowers vmax
uncompetitive inhibitors
bind only to tne enzyme substrate complezx and essentially lock the substrate in the enzyme preventing its release
irreversible inhibiton
active site is made unavailabe for a prolonged period of time or enzyme is permanently altered
example of irreversible inhibtion
aspirin
allosteric enzymes
alternate btwn an active and inactive form
actiavator will result in shift that makes active site more available for binding to substrate where as inhibitor will make it less availbal e
covalently modified enzymes
activated or deactivated by phosphorylation or dephosphorlyation
zymogens
contain catalytic active domain and regulatory domain
regulatory domain must either be removed or altered to expose the ative site
apoptotic enzymes exnhibit similar regulation
most zymogens have sufix - ogen
collagen
characteristic trihelical fiber
makes up most of the EM of connective tissue
elastin
important component of EM
strethc then recoil like a sping
keratin
intermediate filamnt proteins - found in epithelial cells
contribute to mechanical integrity of cell and function as regulatory proteins also
actin
microfilmamtns and thin filaments in myofibrils
most abundant protein in eukaryotic cells
positive and negative side - polarity allows motor proteins to travel unidirectionally along an actin filamenttu
tubulin
microtubules
structure, chromosome separation
negative end = adjacent to nucleus
positive end = perihpery of cell
primary structural proteisn in body
collagen
elastin
keratin
actin
tubulin
cold elephants kill angry tigers
motor proteins
use ATP to power conformation changes associated necessary for motor function
myosin
interacts with actin
celluar transport
single head and neck
mvmt at neck = sarcomere contraction
kinesins and dyenins
kinesins align chromosomes during metaphase and depolymerize microtubules during anaphase of mitosis
dyneins involved in sliding movement of cilia and flagerlla - both important for vesicle transport
kinesins bring vesicles toward positive end
dyneins bring vesicles toward negative end
cell adhesion moleculs
protins found on surface of most cells and aid in binding cell to em or other cells
cadherins
glycoproteins that mediate calcium dependent cell adhesion
often hold similar cell types tgt , like epithelial cells
integrins
two membrane spannin chains alpha beta
cellular signalling
selectins
bind to carb molecs that project from other cell surfaces
expresssed on white blood cells and endothelial cells that line blood vessels
host defence
when antibodies bind to target antigens, three outcomes
neutralize antigen making pathogen or toxin unable to exert effect on body
marking pathogen for destruction by other wbc immediatley - opsonization
clumping together he antigen and antibody into large insoluble protein complexes that can be phagocitozed and digested by macrophases
