Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
30 Cards in this Set
- Front
- Back
|
Myoglobin and Hemoglobin bind oxygen at iron atoms in Heme
|
When iron is oxygenated it becomes in the plane and out of plane for deoxygenated
|
|
|
The structure of Myoglobin prevents the release of reactive oxygen species
|
This causes a formation of the ferric ion and a superoxide anion and becomes metmyoglobin which can not bind oxygen
|
|
|
Hemoglobin provides more oxygen transport (66%) and myoglobin has (7%)
|
Oxygen binding changes quaternary structure of hemoglobin
|
|
|
Two models of Hemoglobin cooperativity.
|
Concerted model: can exist as T or R state where R has a higher affinity of oxygen than T i.e greater equilibrium for R when gains more oxygen.
Sequential Model: conformation change induces changes in neighboring sites without inducting full conversion from T into R |
|
|
2,3 BPG is crucial for determining oxygen affinity of hemoglobin. More BPG more oxygen affinity
|
BPG binds to the center of the molecule
|
|
|
CO2 stimulates release of O2 by two mechanisms
|
High concentration of CO2 drops pH within the RBC and direct interaction of CO2 and hemoglobin
|
|
|
Val and Phe is on surface of a T molecule and in deep when oxygenated
|
More BPG moves oxygen binding curve to the right and gives more oxygen to the tissues
|
|
|
Enzyme specificity is due to precise interaction of the substrate with enzymes, determined by 3D structure of the enzyme
|
Free energy is a useful thermodynamic function for understanding enzymes: the free energy difference between product and reactants and the energy required to initiate the conversion of reactants into products
|
|
|
equilibrium constant= 10^-G/5.69(RT)
|
G=G' +2.30RTlog(product/substate)
|
|
|
G is related to the equilibrium constant and G+ is related to the rate constant
|
Active site of Enzymes have common features: it's the region that binds to the substrates, has catalytic groups, and lowers the activation enrgy of the reaction
|
|
|
Generalization of active sites
|
Active site is a 3D cleft that come from different parts of the amino acid sequences, small part of the total enzyme, unique environments, bound to enzymes by multiple weak interactions, specificity of binding depends on the precisely defined arrangements of atoms in an active site
|
|
|
Two models of bindings: Lock and key: specifice binding
Induced fit model: enzyme changes shape to substrate binding |
First order reaction: directly proportional to the reactants concentrations
|
|
|
Bimolecular reactions: include two reactions
|
Pseudo-first order: concentration of one of the reactant is more than the other
|
|
|
Zero-order: rate is independent of reactant concentrations
|
Michaelis-Menten equation is: Vo=Vmax([s]/ ([s] + Km))
|
|
|
ethanol + NAD with alcohol dehydrogenase gives ethanal + H + NADH
|
ethanal + NAD + H2O with acetaldehyde dehydrongenase gives CH3OO- + H + NADH
|
|
|
Km is a constant and small Km means tight binding and high Km means weak binding
|
Vmax is a constant is never reached
|
|
|
enzymes use two or more substrates and the reactions may be of two reactions
|
Sequential (random or ordered) and Double-Displacement (one or more products are released before all substrate bind to the enzyme
|
|
|
Allosteric enzymes
|
Don't obey MM kinetics, consist of several enzymes and display sigmoidal plots
|
|
|
Irreversible inhibitors can be used to map active sites...three types
|
Group specific reagents (common sense), reactive substrate (the molecule that are structurally similar to the substrate for the enzyme, and suicide inhibitors is the substrate binds to enzyme and is processed
|
|
|
Catalytic antibodies demonstrate the importance of selective binding of the transition state to enymatic activity
|
Can provide insight into catalytic mechanisms, act as inhibitors of enymes, transition and generate catalytic antibodies
|
|
|
6 major classes of enzymes
|
oxidoreductases, hydrolases, transferases, lisases, lyases, isomerases
|
|
|
Covalent catalysis
|
active site that creates a reactive nucleophile that forms a temporary covalent bond (chymotrypsin0
|
|
|
General acid-base catalysis`
|
a molecule other than water plays the role of a proton donor or acceptor (CHYmotrypsin
|
|
|
Catalysis of approximation
|
rate can be enhanced by two substarates together along a single binding surface (NMP kinase
|
|
|
Metal ion
|
just that they can act catalystically ( zine in carbonic anydrase)
|
|
|
Three important amino acids of chymotrypsin
|
histidine, serine (highly reactive alcohol), asparate
|
|
|
Peptide hydrolysis by chymotrypsin (in order):
|
the serine oxygen reacts with a carboxyl group, then the amine group of separate chain reacts with nitrogen on histidine, the hydrogen on separate chain forms temp. bond with the nitrogen, separate nitrogen chain takes the hydrogen from the histidine, water introduced and one hydrogen bonds to histidine and the OH binds to carboxyl group, serine reattaches to histidine, chymotrypsin is reformed, other carboxyl group leaves
|
|
|
Specificity of Chymotrypsion allows binding of residues with long hydrophobic pocket
|
S1 pocket differences between trypsin, elastase chymotrysin: trypsin (asp attracts and stablizes a positvely charged Lys and Arg in the substrate. elastase - valine residues closes the pocket so only small side chains can enter
|
|
|
Specific proteolysis is a common means of activating enzymes and other biological molecules
|
Digestive enzymes, blood clotting, protein hormations, fibrous protein, development process, programmed cell death
|
|
|
Regulation of enzymatic activity
|
Allosteric control- proteins contain distinct regulatory sites and multiple functional sites
Multiple froms of enzymes Reversible covalent modification Proteolyic activation- enzymes travel between active and inactive state Controlling the amount of the enzyme present |
