nature of enzymes

What is the structure of enzymes?

• tertiary globular proteins

• held in shape by hydrogen-bonds, disulphide bridges and ionic bonds

What are properties of enzymes?

• globular tertiary proteins acting as a biological catalyst - speeds up metabolic reactions - enzyme not used up or changed - catalyse many reactions per second 

What are enzymes?

• biological catalysts 

• speeds up chemical reactions but remains unchanged at the end

explain the lock and key model. 

• enzymes are specific 

• only have 1 substrate 

• enzyme has a specific active site which is complimentary to the substrate 

• the substrate binds to active site as a result of successful molecular collision 

• forms an enzyme-substrate complex 

• product is released 

• enzyme is unchanged and ready to be used again

how is the induced fit model different to the lock and key model? 

• active site is flexible and may not be exactly complimentary 

• active site shape slightly changed to fit the substrate shape. 

• active site becomes fully complimentary upon binding. 

• occurs with the enzyme lysozyme. 

How does an enzymatic reaction work in the induced fit model?

• the enzyme active site comes into contact with the substrate by successful random molecular collision

• close fit brings molecules close together and in correct orientation for reaction to take place.

• causes stressing and distortion of chemical bonds of the substrates

• causes hydrogen bonds to break and new bonds form

• makes it easier for substrate to be changed into product and hence lowering activation energy needed

What is anabolism?

two small substrate molecules are combined to form a single larger product molecule - requires energy

What is catabolism?

breaking down large complex substrate molecules into two or more smaller product molecules

Where do enzymes act? 

• extracellular 

• intracellular (solution / membrane bound)

What does extracellular mean?

enzymes secreted from exocytosis and catalyse extracellular reactions (outside cell)

What does intracellular in a solution mean?

solution inside cells- enzymes that catalyse glucose break down in glycolysis

What does intracellular in a membrane bound organelle mean?

enzymes are attracted to membrane. eg Cristae on the mitochondria

What is the active site in an enzyme? 

• hydrophobic hollow or cleft on the enzyme surface that accepts reactants (substrates and cofactors)

• contain amino acids which - bind reactants + catalyse reaction

Why is the active site hydrophobic?

• water is charged which will block active site for the substrate

• water is polar which will interfere with the charges

What does PH means?

measure of concentration of hydrogen ions in a solution.