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

2. PROTEINS

3. 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

4. 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

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

6. ENZYMES

7. 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

8. 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

9. 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.

10. 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

11. FACTORS AFFECTING ACTIVITY
3.6.3
FACTORS AFFECTING ACTIVITY

12. 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

13. 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

14. 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.