Biochem quiz 1 enzyme kinetics Flashcards
types of enzymes and their function
What do ligases do?
Catalyze Condensation reactions using ATP as energy source.
Ezymes speed up a reaction by..
Decreasing activation energy, stabilize the transition state, lower activation energy
what is the role of oxioreductases?
oxidation reduction reactions, transfer of electrons or addition of oxygen
what does a ligase do? what is it’s function?
ligation of two substrates coupled to cleavage of ATP. Catalyze condensation reactions by utilizing ATP as an energy source.
Enzymes are ______at the end of a reaction
unchanged
How do cofactors play a role in enzyme kinetics?
Cofactors are non-proteins , commonly ions or organic molecules known as coenzymes. Certain enyzmes need cofactors for activity. ** co factors facilitate catalytic reactions
what are the different types of cofactors?
inorganic- metal ions and organic- coenzymes that can bind to Fe2+ such as heme
Name the oxidation-reduction cofactors
Nad+, Fad, Coenzyme Q
NAD+
accepts 2 e- and 1 H+ to form reduced NADH. Non covalently attached to enzyme.
FAD
can accept 2 electrons and 2 H+, covalently attached to enzyme. Derived from riboflavin. Forms FADH2.
used in oxidative phosphorylation
Coenzyme Q
can accept 2 electrons and 2 H+ . shuttles reducing equivalent to the inner mito. membrane.
Also known as ubiquinone, used in ETC
What is NAD+ derived from?
Niacin , Vitamin B3
Activation co factors: list and describe their function
form covalent bonds with the substrate. TPP, acetyl coA, Biotin, PLP
What is the role of TPP?
removes Co2 from alpha-keto acids, derived from thiamine, forms a carbanion that binds with Keto groups, involved with decarboxylation
What is the role of Coenzyme A?
reactive thiol group forms exergonic thioester with acyl groups. Shuttles acyl groups between enzymes. Used at three locations in CAC
What is the role of biotin?
activation transfer of Co2 requires energy . Biotin is covalently bonded to lysine in carboxylases. It’s reactive N covalently bonds to Co2 and requires energy.
What is the role of PLP?
activation transfer of amino groups and Co2 groups. covalently bonded to the enzyme - schiff base link to enzymes
The rate of enzyme catalyzed reaction depends on______
depends on the amount of Kcat and E:S
When {S} is near Km, how does this effect the reaction velocity?
The reaction velocity becomes sensitive to changes.
Competitive enzyme inhibitors do what to Km?
Km Increases, Vmax stays the same.
What does the Y axis of a lineweaver burke plot show?
1/Vmax
what are the two types of inhibition?
Irreversible and reversible
types of reversible inhibition
competitive, non competitve, mixed /non comp.
non competitve inhibition
not affected by binding of inhibitor, DECREASES VMax but does not affect Km
Allosteric enzymes
inactive and active confirmations. Modifiers bind at sites other than active site.
** Change the activity of the receptor of the enzyme
regulation of enzymes: protein protein interactions
changes in confirmation of the active site can be regulated by protein-protein interactions I.e g proteins and caulmadulin
When g proteins bind with gtp, they change shape and interact with proteins, undergo confirmational changes
proteolytic cleavage
IRREVERSIBLE some enzymes must undergo this to be functional. i. e. regualtion of proteases
What is the role of isoenzymes?
enzymes that catalyze the same reaction but differ in their physiochemical and kinectic properties. Can be used to locate the site of tissue damage.
Name diagnostically significant enzymes:
bone
alkaline phosphotase
name the diagnostically significant enzyme that correlates to the liver:
alanine aminotransferase
name the diagnostically significant enzyme associated with the heart and skeletal muscle:
creatine kinase
name the diagnostically significant enzyme associated with the pancreas:
triacylglycerol lipase
Elisa tagging/identification
can be used to measure amounts of hormones in the bloods,viruses or proteins. the intensity of color is proportional to the amount of antigen present. Tag is an enzyme that converts substrate into a colored product.
Why are enzymes useful in clincal diagnosis?
one or more enzymes released in circulation due to injury may show where injury occurred. Genetic differentiation results in differences in expression of enzymes.
non competitive inhibition- how does if affect Km and vmax?
decreases Vmax but does not affect Km. substrate binding is not affected by the inhibitor.
what cofactor’s oxidation state changes after catalysis?
NAD+
Vmax
fully saturated, maximum velocity
When is the reaction velocity more responsive?
When substrate concentration is LESS than Km. Reaction velocity will be more sensitive to changes when Km is close or equal to concentration, or when concentration is less than Km.
What does a small Km symbolize?
Small Km signifies a high affinity of enzyme for the substrate.
All enzyme inhibitors_____ the velocity of a reaction.
Decrease
Where does the substrate bind in competitive inhibition?
the substrate binds to the active site and competes off the inhibitor.
Competitive inhibition changes what?
increases Km, Vmax stays the same
uncompetitive inhibition
lowers Km, doesnt change Vmax. Does not bind to the active site.
Non competitive inhibitor
inhibitor has no affect on substrate binding to active site. Lowers Vmax , has no affect on Km
How does the presence of NADPH illustate enzyme activity?
NAD+ is colorless, NADPH shows color so color change indirectly reports the amount of gluc-6-phos produced by hexokinase.
