Řӟƒƪӟςϯїδή 4 ώӟӟʞ 6

Hey peeps it’s Neerie here, thinking about how time is flying sooooo fast and I am already in week 6 of my second semester as a year 1 student…yaayy!!! Well…today we started  ЀлӠұϻӟŞ. As you all should know enzymes are biological catalysts. Why is enzymes called biological catalysts? Well…it’s simply because they are large molecules that speed up the chemical reactions inside cells. Each type of enzyme does on specific job. Enzymes are protein in nature which are made from long chains of different amino acids.

Enzymes are soluble protein molecules that can speed up chemical reactions in cells. These reactions include respiration, photosynthesis and making new proteins. For this reason enzymes are sometimes called biological catalysts. Enzymes speed up (catalyse) chemical reactions occurring inside and outside of living cells including:

  • DNA replication
  • Protein synthesis
  • Digestion

Each enzyme will only speed up one reaction as the shape of the enzyme molecule needs to match the shape of the molecule it reacts with (the substrate molecule). The part of the enzyme molecule that matches the substrate is called the active site.



A few points to note about this graph:

  • it is an exothermic reaction
  • the reactants for both the catalyzed and uncatalyzed reactions start at the same point
  • the enzyme only lowers the activation energy from Ea (blue) to Ea (pink)

There are three distinctive features of enzymes:

  • catalytic power
  • specificity
  • regulation

There are 6 major classes of enzymes:

Only Think His Love ILiving each day with you and only you in mind :p lol (an easy way to remember the order of classes in exams)

  • Oxidoreductase
  • Transferase
  • Hydrolase
  • Lyase
  • Isomerase
  • Ligase
Oxidoreductase: Oxidoreductases catalyze oxidation reduction reactions.  At least one substrate becomes oxidized and at least one substrate becomes reduced.
Transferase:  Transferases catalyze group transfer reactions- the transfer of a functional group from one molecule to another.
Hydrolase:  In hydrolysis reactions, C-O, C-N, and C-S bonds are cleaved by addition of H2O in the form of OH and H+ to the atoms forming the bond.
Lyase: Lyases cleave C-C, C-O, C-N, and C-S bonds by means other than hydrolysis or oxidation.
Isomerase: Isomerases just rearrange the existing atoms of a molecule, that is, create isomers of the starting material.
Ligase: Ligases synthesize C-C, C-S, C-O, and C-N bonds in reactions coupled to the cleavage of high energy phosphate bonds in ATP or some other nucleotide.

Enzymes and temperature relationship:

At low temperatures enzymic reactions are slow but increases as the temperature rises until an optimum temperature is reached. After this point the reaction will slow down and eventually stop. This is where protein denaturation has taken place.


Enzymes and pH relationship:

Most enzymes work fastest in neutral conditions. By making the solution more acidic or alkaline it will slow the reaction down. At extremes of pH the reaction will stop altogether.


Enzymes and substrate concentration:

Enzymes will work best if there is a lot of substrate available. As [S] increases so does the enzyme activity. However, the enzyme activity does not increase without end. This is because the enzyme can’t work any faster even though there is plenty of substrate available.

What is Denaturing of enzymes???

The important part of an enzyme is called the active site. This is where specific molecules bind to the enzyme and the reaction occurs.

Anything that changes the shape of the active site stops the enzyme from working. The shape of the active site is affected by pH and temperature.