REVISION: PROTEINS & ENZYMES Topic 3 IB Biology 2014 Miss Werba

PROTEINS

PROTEIN WORDS Proteins or polypeptides = long chains of amino acids 3.2.2 PROTEIN WORDS Proteins or polypeptides = long chains of amino acids Monomer = amino acid Dimer = dipeptide Polymer = peptide or protein

AMINO ACID STRUCTURE a central carbon atom 4 side groups: 3.2.2 AMINO ACID STRUCTURE a central carbon atom 4 side groups: the amine group (-NH2) the carboxylic acid group (-COOH) an H group the R group – R standing for “the rest” rather than an element

FORMATION OF PROTEINS (CONDENSATION REACTIONS) 3.2.5 FORMATION OF PROTEINS (CONDENSATION REACTIONS)

ENZYMES

3.6.1 ENZYMES Enzymes are biological catalysts, which speed up the rate of chemical reactions without becoming a part of the products. Without enzymes, chemical reactions would still occur but very slowly. Enzymes are proteins with a unique shape. Many enzyme names end in –ase eg: amylase, catalase, sucrase, lipase

HOW THEY WORK Lock and key model 3.6.1 3.6.2 HOW THEY WORK Lock and key model ie. enzymes are designed to “fit” the shape of their substrate Unique portion of an enzyme is its active site ie. a groove or cleft on the surface of the enzyme which the substrate molecule can bind to

3.6.1 3.6.2 HOW THEY WORK enzyme substrate enzyme-substrate complex enzyme-product complex enzyme product The product will detach from the enzyme, leaving the active sites free for the attachment of other substrate molecules.

DENATURATION Denaturation: 3.6.4 DENATURATION Denaturation: changing the structure of a protein so that it can no longer carry out its function Usually permanent. Can be caused by high temperatures and extremes of pH. Breaks bonds holding the 3D (tertiary) structure of a protein together  loss of shape/function

FACTORS AFFECTING ACTIVITY 3.6.3 FACTORS AFFECTING ACTIVITY

FACTORS AFFECTING ACTIVITY 3.6.3 FACTORS AFFECTING ACTIVITY Temperature Inactivated at low temps  become dormant Denatured at high temps  bonds are broken  active site shape changes enzyme become useless pH Denatured at wrong pH enzyme become useless Substrate concentration Enzyme activity is directly proportional to substrate concentration at low substrate concentrations  more active sites  greater efficiency Enzyme activity plateaus at high substrate concentrations  active sites all in use at maximum efficiency already

FACTORS AFFECTING ACTIVITY 3.6.3 FACTORS AFFECTING ACTIVITY TEMPERATURE pH SUBSTRATATE CONCENTRATION Too low Inactivated (dormant) Denatured Enzyme efficiency is high Too high Enzyme efficiency plateaus

INDUSTRIAL EXAMPLE: LACTASE 3.5.5 INDUSTRIAL EXAMPLE: LACTASE 70% of adult humans = lactose intolerant They have lost the ability to produce lactase after early childhood. Ingestion of milk will lead to excess gas production & diarrhoea. The food industry has produced lactose-free milk. Use lactase enzyme to break down lactose into glucose and galactose. Milk tastes sweeter but will not cause reaction in lactose-intolerant adults.