Enzymes

Question 1

What is an enzyme?

Answer 1

• Enzymes are biological catalysts.
• molecules made up of living cells.
• ## Most enzymes are made up of protein and are globular. There is a group of enzymes called ribozymes which are composed by RNA like peptide transferase

Question 2

What does an enzyme do?

Answer 2

-catalyse metabolic reactions and enable metabolic reactions in living organisms to proceed rapidly at low temperatures
-ensure metabolism proceeds stepwise in an orderly fashion

Question 3

Without enzyme what happens?

Answer 3

• Reactions that occur in living organisms occur too slowly for life to be sustained
• We can raise the temperature to increase speed of reactions, but it would kill the cells and organisms,proteins become denatures and membranes disrupted. SO energetically very expensive

Question 4

What is metaboilsm? Which is catabolism and anabolism

Answer 4

Anabolism - synthesis of molecules from smaller molecules and usually requires ATP. This usually also involves condensation (water molecule removed)

Catabolism - Breakdown of molecules and usually release energy stored in the bonds. This usually involves oxidation or hydrolysis. (Water molecule used)

Question 5

Properties of enzymes 6

Answer 5

1. Enzymes are highly specific in their action.
   - Most enzymes only act on one type of substrate molecules while others act on a group of highly similar substrate molecules
2. Enzymes are effective in small amounts.
   - A very small amount can bring about the conversion of large amount of substrates.
   - As they remain chemically unchanged at the end of reactions they catalyse,
   -thus can be reused.
3. Enzymes are very efficient
   - proceed 10^3-10^8 times faster
   - have a high turnover when enzymes are fully saturated with substrate (substrate molecules turned into products by one molecule of enzyme in one second )
   -speed up rate of both forward and backwood reaction
4. presence of enzyme does not alter the nature of properties of end-products the reaction
5. Enzymes are soluble in water
   - work in aq environment in living cells
6. Activity of enzymes affected by temperature,pH,enzyme concentration,substrate concentration and presence of activators and inhibitors

Question 6

Naming and classification of Enzymes

Answer 6

Kinases - phosphate groups transferred from ATP to specific substrtate (phosphorylation) , thus makes the inactive protein become active
Phosphatases - remova, of phosphate grps from the substrate (dephosphorylation)
Oxidoreductases- catalyse oxidation and reduction reactions
Transferases- transfer functional group to specific substrate
Hydrolases- water required to break down substrates
Ligases- catalyse the joining of 2 molecules by forming new chemical bond
Isomerases- catalyse inter conversion of isomers

Question 7

Mode of an enzyme

Answer 7

1. Active site
   - depression on the surface where substrate enters and binds to to form enzyme-substrate complex
   - has specific 3D conformation and distribution of charge which only substrate complementary will fit
   - 3 type of amino acid residue which are catalytic(catalyse Reaction, act on bonds in substrate to be broken), contact(ensure specific conformation ), structural (maintain overall globular shape)
   - catalytic and contact residue make up active site, far apart but when folded are in close proximity
2. Activation energy
   - Initial investment of energy before start of reaction
   -enzyme will lower activation energy so reactions can take place faster
   2 ways- hold substrate close tgt at correct orientation and angle at active site for successful interaction and collision (anabolic )OR straining chemical bonds of substrate until they break (catabolic)
3. Enzyme specificity
   - highly specific as catalyse on particular type of substrate molecule
   - due to substrates of only complementary base shape will enter and bind to an active site with specific 3D conformation
   - and enzyme and substrate must be chemically compatible (charge and hydrophilic or hydrophobic complementarity- chemical fit )

Question 8

Lock and key hypothesis