Lecture 3: Enzymes Flashcards
1
Q
enzymes
A
biological catalyst that speed up a chemical reaction without being consumed in the process
2
Q
chemical nature
A
they are globular proteins except for a small group of RNA molecules
3
Q
properties of enzymes
A
- are not consumed in reactions
- highly specific
- reaction catalysed is reversible
- do not affect equilibria of reaction
4
Q
A
4
Q
A
5
Q
mechanism
A
- speed up a reaction by providing alternative pathway of reaction with lower activation energy facilitating formation of transition state
5
Q
Gibbs free energy(ΔG’)
A
difference in free energy between the transition state and substrate state
aka activational barrier
5
Q
endorgenic reaction
A
- does not release free energy
- requires input of energy to proceed
- +ΔG
5
Q
exergonic reation
A
- -ΔG
- gives off free energy
- reaction is spontaneous i.e proceeds without input of energy
5
Q
ΔG=0
A
reaction is in equilibrium
5
Q
Active site
A
- 3D cleft lined with amino acid residues that are critical in making and forming bonds, binding to a substrate ligand
- where the transition state occurs
- takes a small part of the enzyme
- H bonds, electrostatic forces, VDW forces and hydroohobic interactions
5
Q
Thermodynamic equation
A
ΔG=ΔG*’ +RTln[prod]/[reactants]
* Keq=[prod]/[reactants]
R= 1.987×10^-3Kcalmol-1k-1
6
Q
Lock and key model
A
- active site is lined up with amino acid residues complementary to the subrate in terms of shape size, charge
6
Q
Nonfunctional enzymes
A
- arise from destruction of cells, leukocytes, erythrocytes etc
- tissue damage or disease is accompanied by increase of these
- hence they can aid in diagnosis
6
Q
Induced fit model
A
- exposure of enzyme to the substrate induces a conforational change in enzyme
- changing the shape of active site
- allowing substrate and eznyme to bind tightly
