Enzymes Flashcards
What do proteases do
Hydrolyze peptide bonds
What is papain
A type of protease that has low specificity (cleave any peptide bond)
What is trypsin
A protien that helps break down dietary polypeptides
Higher specificity (cleaves after lys or arg only )
What is thrombin
Highest specificity
Only cleaves after arg
What is group specificity
Absolute specificity
Group: the enzyme cleaves any substrate with a certain FUCTIONAL group
Absolute: the enzyme has only one specific substrate (ex. Lactase only cleaves lactose)
What do enzymes do to the equilibrium of a reaction
They make it so that the same equilibrium point (amount of product) it reached
But the max amount is reached much faster when the enzyme is present so that the reaction is KINETICALLY favourable
What is the equilibrium of a reaction
The forward and reverse reactions occur at the same rate and the concentration of the product is constant
What is delta g in a spontaneous reaction
At equilibrium
Negative, exergonic
Delta g is 0, there’s no energy left for work
What is delta G
Gibbs change in free energy
It’s independent of the path of transformation, it only looks at the change in energy from products to reactants
Tells us nothing about the rate of the reaction
What are standard conditions
Delta g knot
1M
1atm (for gas)
298K
What is the conversion of delta g for biochemistry
Delta g knot prime
PH Of 7
It’s found by measuring keq (the reactant over product at equilibrium)
When H is a reactant it’s concentration is 1M
Spontaneous reactions are ___
Not instantaneous
How do enzymes accelerate reactions?
They lower the activation NRG (G#) to overcome the activation energy barrier (energy taken to go from reactant to intermediate)
How do enzymes lower the activation NRG
The stablize the transition state (the short lived intermediate between the substrate and the product)
X#
Where does the energy come from to help lower the activation energy of a reaction
When the enzyme binds to the substrate and many weak interactions occur, free energy is released
This free energy is called binding NRG
When do maximum binding energy occur
During the transitions state, when the enzyme is interacting with the transition state
What maximizes the amount of binding energy
Only the correct substrate binding to the enzyme can maximize, so this involves specificity
What are 5 feature of the enzymes active site
The residues forming the active site come from different positions in the protiens sequence but are brought close cause of the 3D shape
Takes up a small volume/amount of the total protien
Has a unique micro environment
The active site residues Form many weak instactions with substrates
The specificity of substrate binding depends on the specific arrangement of the atoms in the active site
What are cofactors
Non protien compunds that bind to protiens and are needed for biological activity (enzyme activity)
Include coenzymes and metals
What are coenzymes
Type of co factor that is made of vitamin derived organic molecules
What are metals
Type of cofactor that are just metals the help catalyze
What are enzymes with cofactor called
Without
Holoenzyme
Apoenzyme
What is a prosthetic group
What is a cosubstrate
The cofactor binds very tightly to the enzymes, basically in there permanently
The cofactor binds to the enzymes and then is released after each reaction is complete (not permanent)
What are examples of Coenzyme COfactor
Nad+ from vitamin B3 (niacin) Gets reduced to NADH
Can also be oxides from NADH to make NAD+
Ex. The NADH bind to pyruvate and lactate dehydrogenase (enzyme) to get oxidized and form lactate from pyruvate
What do metal cofactors do
Ex. Zinc bind to water and decreases it pka so it can deprotonated at ph 7
Then to o- of the water attacks co2 and makes carbonic acid
This all wouldn’t happen without the cofactor decreasing the pka
What is the induced fit model of enzymes
The enzymes active site changes to be complementary to the substrate after it has binds (molds around it like playdoh)
What is the lock and key model
The enzyme and substrate are already a perfect fit for each other , not moulding or reshaping occurs
Outdated model
