Lecture 9 -enymeeee Flashcards
Life is
Inputs
And
Outputs
For any chemical or biological processes, there is a
Change in free energy, ^G
^G<0
Gibbs free energy
Total free energy in a system - enthopy and entropy
^G>0
Non-spontaneous; energy required
^G = 0
A
Life is not at…
Equilibrium
Spontaneous does not mean…
Fast
Whether someone is spontaneous depends on the ______ of the reaction, the rate of reaction depends on the _____
Energy (thermodynamics)
Speed (kinetics)
Biochemical synthesis and ______ usurps pathways of _____-______ steps. The network keeps (most) _____ _____ way from ______.
Biochemical synthesis and segregation uses pathways of enzyme-catalysed steps.
- the metabolic network keeps (most) individual steps away from equilibrium - if your at equilibrium work isn’t going to happen
How does coupling work?
Enzymes can couple a spontaneous reaction to a non-spontaneous one, to make the overall ^G < 0
Enzymes keep reactions away from..
..equilibrium
- at equilibrium no work happens
Spontaneous does not equal
Fast
Reactions pass through high energy…
Transition states
What is required tho reach a transition state
Activation energy
Activation energy is required to reach…
The transition state
If reactants have more energy then the products…
… is a negative G
- will happen spontaneously
To get from reactants to products… must past through…
Transition state
Transition state of graph
What is activation energy?
Difference between reactants and transition state
Activation energy determines
How fast reaction will proceed
Enzymes can reduce
Activation energy of a particular reaction
Enzymes…
… catalyse thermoduynamically favourable reactions by
By decreasing activation energy of reaction…
Enymes accelerate the forward and reverse reactions equally
- mainly effect speed and kinetics
When enzymes decrease activation energy and accelerate the forward and backward reactions, what happens to ^G
The overall ^G for the reaction is not changed
What are enzymes ?
Proteins
Occasionally RNA
What is an example of an enzyme
-glycogen phosporylase resaleses glucose from glycogen
Glycogen: stable store of glucose that is released when required by
Why is it called glycogen phosphylase ?
- it takes a phosphate group and attaches phosphate onto terminal glucose of the glycogen
- this makes glucose-1 phosphate
Why is enzyme needed
- cos although reaction is spontaneous, without a lowered activation energy it will take fucking ages for it to reach the activation energy
- decreased half life
Classes of enzymes
- oxidoreductases
- transferases
- hydrolases
- lyases
- isomerases
- ligases
Oxidoreductases
Redox (transfer of electrons)
Transferases
Transfer of a functional group
Hydrolases
Hydrolysis reactions (using H20)
Lyases
Non-hydrolysis breaking or making of binds (not using H2O)
Isomerases
Transfer of atoms/groups within a molecule to yield an isomeric form
Ligases
Join two molecules together (i.e to form a new bond; usually coupled to ATP cleavage)
Many enymes require other non-protein _____ to help them _______ ______
Many enzymes require other non-protein ‘factors’ to help them catalyse reactions
- they provide chemical properties that can’t be provided by basic amino acid chain
Two classes of cofactor
- metal ions
- coenzymes
What kind of reactions are metal ions good co-factors for and why
They participate in acid-base catalysis as they are Lewis acids (i.e election acceptors)
What does the cofactor metal ions form? What is that good for?
Form coordination compounds with precise geometries ( good for positioning reactants exactly where they need to be)
Examples of metal ions
Mg2+ : DNA polymerase; hexokinase; pyruvate kinase
Zn2+: alchohol dehydrogenase; carbonic anhydrase
Fe2+ or Fe3+ : cytochrome oxidase; peroxidase
What are coenzymes?
- small organic molecules
- co-substates
- carriers (of electrons, atoms or functional groups)
- are often derived from vitamins
What is essential for coenzymes
Vitamins
What cofactor facilitates glycogen phosphorlase activity
PLP
What does PLP do?
facilitates glycogen phosphorlase activity
How does PLP facilitate glycogen phosphorlase activity ?
PLP gets covalently attached to lysine residue within the active site of that enzyme which sits right next to the reactant
- PTM side chain at the heart of the enzyme
- really good for donating proton to the phosphate group that needs to be transferred
NOT USED UP DURING REACTION
Reactions will proceed if
Kept away from equilibrium
Enzymes couple ________ to _________
Enzymes couple spontaous reactions to non spontaneous e reactions
- otherwise you get stuck in metabolic pathway
Enymes catalyse thermodynamically favourable reactions by lowering the activation energy
Yep
Key concepts
- Life is a network of reactions that is not at equilibrium (thus enabling useful work to be done)
- enzymes increase reaction rates by lowering the energy required to reach the transition state
- cofactorea are often required for catalysis (which is also why they’re required for your diet
Life is a network of reactions that is not at equilibrium thus
Enabling useful work to be done
Enzymes increase reaction rates by…
Lowering the energy required to reach the transition state
Cofactors are often required for
Catalysis, which is why they’re required in your diet
