1. PROTEINS
INTRODUCTION

7. Useful Proteins
There are thousands and thousands of different combinations of amino acids that can make up proteins and that would increase if each one had multiple shapes
Proteins usually have only one useful conformation
Natural selection has eliminated proteins that do not perform a specific function in the cell

8. Functions / importance of Proteins
Type Examples
Structural tendons, cartilage, hair, nails
Contractile muscles
Transport hemoglobin, albumin
Storage ferritin
Hormonal eg. insulin, growth hormone
Enzyme eg. hydroxylases
Protection immunoglobulins
Energy k.cal/gm Motor
Signalling
Receptors
Motor proteins kinesin

9. Protein Families Enzymes
Have similarities in amino acid sequence and 3-D structure
Have similar functions such as breakdown proteins but do it differently

10. Proteins at Work
The conformation of a protein gives it a unique function
To work proteins must interact with other molecules, usually 1 or a few molecules from the thousands to 1 protein
Ligand – the molecule that a protein can bind
Binding site – part of the protein that interacts with the ligand
Consists of a cavity formed by a specific arrangement of amino acids

11. Ligand Binding

12. Enzymes as Catalysts
Enzymes are proteins that bind to their ligand as the 1st step in a process
An enzyme’s ligand is called a substrate
May be 1 or more molecules
Output of the reaction is called the product
Enzymes can repeat these steps many times and rapidly, called catalysts

14. Enzymes at Work
Lysozyme is an important enzyme that protects us from bacteria by making holes in the bacterial cell wall and causing it to break
Lysozyme adds H2O to the glycosidic bond in the cell wall
Active site is a special binding site in enzymes where the chemical reaction takes place

15. Antibodies
Y-shaped molecules with 2 binding sites at the upper ends of the Y
The loops of polypeptides on the end of the binding site are what imparts the recognition of the antigen
Changes in the sequence of the loops make the antibody recognize different antigens - specificity

16. Antibodies

17. Antibody Family
A family of proteins that can be created to bind to almost any molecule
Antibodies (immunoglobulins) are made in response to a foreign molecule ie. bacteria, virus, pollen… called the antigen
Bind together tightly and therefore inactivates the antigen or marks it for destruction

18. Motor Proteins
Proteins can move in the cell, say up and down a DNA strand but with very little uniformity
The hydrolysis of ATP can direct the the movement as well as make it unidirectional
The motor proteins that move things along the actin filaments or myosin

19. Protein Machines
Complexes of 10 or more proteins that work together such as DNA replication, RNA or protein synthesis, trans-membrane signaling etc.
Usually driven by ATP or GTP hydrolysis