Term
enzymes > reaction rates
they remain unchanged after the reaction
the chemicals acted upon are called substrates
the end point is the products
are all enzymes proteins? |
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Definition
| most but not all enzymes are proteins eg, some rna so enzyme activity |
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Term
enzymes show specificity this can be low, moderate or high. give an example of each.
extra: Lysine and Arginie are positively charged amino acids |
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Definition
low specificity - subtisilin, a bacterial protease that cleaves peptide bonds
moderate - Trypsin, digestive enzyme that cleaves peptide bonds on the carboxyl sides of Lys or Arg
high - Thrombin - blood clotting enzyme that cleaves between Arg and Gly within specific amino acid sequence motifs. |
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Term
most enzymes end in ASE
what is the difference between ASE and SYNTHASE?
eg ATPase V ATP synthase |
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Definition
-ASE usually breaks shit down
-SYNTHASE makes products |
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Term
| proteolytic enzymes usually have which ending? |
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Definition
-IN
eg trypsin and pepsin. |
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Term
how are enzymes classified?
how many numbers are used to describe enzyme classification? |
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Definition
enzymes classified using the Enzyme Classification System - EC Numbers derived from the international union of Biochemistry and molecular biology
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Term
| what do the four EC numbers represent? |
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Definition
- 1st digit from 6 major enzyme classes
- 2nd and 3rd digits give further details for type of reaction
- 4th digit gives substrate
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Term
| name groups 1,2 and 3 from enzyme classification and say what they do |
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Definition
1. Oxidoreductases - transfer of e- (hydride ions or H atoms)
2. Transferases - group transfer reactions
3. Hydrolases - hydrolysis reactions (transfer of functional groups to water) |
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Term
| name groups 4,5 and 6 from enzyme classification and say what they do |
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Definition
4 Lyases - addition of groups to double bonds, or double bond fromation by removal of groups
5 Isomerases - transfer of groups within molecules to yield isomeric forms
6 Ligases - formation of C-C, C-S, C-O and C-N bonds by condensation reactions coupled to ATP cleavage |
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Term
| what is the trivial name for L-histidine carboxylase? |
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Definition
hisitidine decarboxylase
the EC number for this enzyme is 4.1.1.22
class 4 lyase, C-C- bond broken, Carboxyl group removed, substrate formed |
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Term
| how is enzyme activity measured? |
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Definition
by the rate of reaction. this is the amount of product produced per unit time.
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Term
the SI unit to measure enzyme activity is in Katal (kat) this is in moles/seconds
explain this |
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Definition
it is the amount of an enzyme that converts 1 mol of substrate per second under standard assay conditons
however a mole is a large number and a second is very little so biologists tend to use the International activity unit |
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Term
the Internationa activity unit (U) is measured in (umoles/min)
define this |
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Definition
| an amount of enzyme that will catalyse the transformation of 1 micromole of the substrate per minute under standard assay conditions. |
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Term
| with regards to thermodynamics, which type of reactions occur spontaneously? |
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Definition
exergonic reactions.
however even in an exergonic reaction, the reactants must absorb energy from their surroundings to break bonds before new bonds can form and release energy. |
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Term
| reactions that require overall input of energy do not occur sponataneously are known as? |
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Definition
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Term
activation energy is the initial input of energy required to get reactants to the transition state. this is also known as Gibbs free energy of activation or simply Ea.
what does activation energy do? |
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Definition
| it increases the speed of reactant molecules creating more powerful collisions making the reactants unstable. |
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Term
Ea is the amount of energy necessary to push the reactants over an energy barrier.
what is the difference between the free energy of the products and free energy of the reactants known as? |
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Definition
ΔG
this is different to the symbol for Gibbs free energy of activation whihc has the symbol
ΔG¥ (delta G dagger) |
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Term
| at which state are the molecules unstable? start, transition or end? |
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Definition
the transition state
the difference between the free energy of the reactants and the transition state is known as ΔG¥ or Ea (activation energy) |
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Term
enzymes work by reducing the activation energy. they speed up reactions by doing this.
the transition state can be reached even at moderate temperatures.
do enzymes chage Delta G? |
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Definition
however enzymes do not change ΔG. they just hasten the reactions that would eventually occur
enzymes affect forward and backward rates equally and allow you to reach equlibrium faster. |
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Term
| the enzyme will bind to substrate but which state does it have a higher affinity for? |
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Definition
the transition state
the first step of an enzyme catalysed reaction si the formation of the enzyme substrate complex |
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Term
| Emil Fischer came up with which hypothethis regarding the enzyme-substrate complex in 1890? |
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Definition
the Lock and Key Hypothethis
here the enzymes active site is the lock and the substrate is the key and when the substrate fits the active site of the enzyme we get the formation of the ES complex |
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Term
| define Transition state analogues using Pauling's hypothethis |
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Definition
Pauling's hypothesis predicts that the transition state binds more strongly to the enzyme than the substrate
transition state analogues have very high affinities for enzymes eg the transition state analogue binds 100,000 000 more tightly to yeast adenosine deaminase than the substrate adenosine |
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