L10 - intro to enzyme function Flashcards
outlines
- know how enzymes catalyse their reactions in a thermodynamics state
- how enzymes catalyse their reactions in a chemical sense
- different classes of enzymes
- how chymotrypsin catalyses its reaction
what is a enzyme?
- proteins
- catalyse conversion of substrates to products
- remain chemically unchanged at end of reaction
- do not change eqm position of reaction
- fold into specific 3d shape for its activity
what are the 2 models of catalysis
- lock and key
- induced fit
most enzymes use both strategies
explain enzyme catalytic cycles
Substrate joins AS
Forms enzyme substrate complex
Catalysis occurs forming enzyme product complex
Then you get product
describe thermodynamic catalysis by enzymes
- enzymes lower activation energy of reaction
- Uncatalysed reaction: substrate at higher energy, product in lower (thermodynamically favourable)
why can we not just heat up biochemical systems to speed up ROR
proteins will denature
binding of substates is ????
SPECIFIC
name the types of interactions enzymes form
- ionic bonding
- hydrogen bonding
- hydrogen bonding to main chain
- h bonds to charged groups
- hydrophobic interactions
describe chemical catalysis of enzyme reactions
- substrates and reacting groups held closely together
- reacting groups orientated correctly to each other
- reacting BONDS are stretched + bent
- the AS usually has hydrophobic groups which can change pKa of charged a.a side chains + substrate groups
- bulk solvent is not part of enzyme AS’s and charged groups aren’t masked
- water molecules (locked into positions on AS) will donate or accept protons
- protons can be donated or accpeted by AS groups (acid/base catalysis)
- nucleophillic catalysis (formation of acyl-enzyme intermediate)
- enzymes can be stereoselective (certain stereoisomers of a substrate will bind)
- enzymes use cofactors (e.g metal ions)
- enzymes use cosubstrates
- these are derived from vitamins and minerals
- AS’s are comp to transition states due to distortion of bond lengths + angles
describe the chemical model of enzyme catalysis
- the smaller the degrees of freedom (the more we restrict the conformation), the higher the reaction rate
- enzymes catalyse reactions into locking the substrate into a fixed position in the AS so they can be accessed by other reacting groups, substrates or an active site residue
type of chem that is important in enzymes
- carbonyl compounds (e.g nucleic acids, lipids, carbs, proteins)
- control of stereochem
- represent things in correct shape (e.g sp3 = tetrahedral geometry)
note: large number of reactions
but only a small number of types of reactions
typical function of a hydrolase
hydrolysis of compounds using water
typical function of a nuclease
hydrolysis of DNA or RNA
typical function of a protease
hydrolysis of protein PEPTIDE BONDS
