LECTURE                                                                      PROTEINS

In this lecture you will learn:


INTRODUCTION
Proteins are the product coded for by DNA.  They have two functions, as enzymes and as structure (muscles).  They are created from amino acids by dehydration synthesis.  As they are made they become functional by folding into secondary, tertiary and even quarternary forms.  In addition to folding, proteins can undergo other post translation modifications  which can give them different functions (next lecture).
 
 
THE BASIC STRUCTURE OF AMINO ACIDS
An amino acid:
-- an alpha carbon to which are covalently bound:
  an amine group (- NH2)
a carboxyl (acid) group (- COOH)
-- a side chain (R group) one of 20 different ones
only twenty different amino acids are used to make PROTEINS

 
DEHYDRATION SYNTHESIS CREATES PROTEINS FROM AMINO ACIDS
- Two amino acids are covalently bonded together to form a peptide/protein by a reaction that removes a molecule of water.  This reaction is called DEHYDRATION SYNTHESIS. 

- The linkage is called a peptide linkage or peptide bond
- There are between 10 and 100 million different kinds of proteins
- Each protein can contain fewer than 100 to more than 500,000 amino acids. 

GO HERE to see dehydration synthesis of amino acids 

"Titin, also known as connectin is a protein .... is important in the contraction of striated muscle tissues. It consists of 34,350 amino acids and the gene for titin also contains the largest number of introns (363) ever discovered in any single gene.[5]"
http://en.wikipedia.org/wiki/Titin

"Albumin consists of 584 amino acids and contains no carbohydrate. Serum albumin is the most abundant blood plasma protein and is produced in the liver and forms a large proportion of all plasma protein. The human version is human serum albumin, and it normally constitutes about 60% of human plasma protein."
http://en.wikipedia.org/wiki/Albumin


 
THE 20 AMINO ACIDS ARE DIFFERENT AT THEIR SIDE "R" CHAINS
EXCELLENT SITE HERE THAT EXPLAINS PHOBIC AND PHILIC WITH NICE ROLLOVER FUNCTION
 

1. some of the side chains arehydrophobic and avoid contact with water, they usually have no charges on the side group.

2. Some have charged side group and interact with water or are hydrophilic

3.  Some are acidic (have COOH  groups) like glutamic acid

4.  Some have amino groups (NH3+)

5.  Some have alcohol -OH groups

6.  Some are neither hydrophobic nor hydrophilic, but are in between.
 

REVIEW QUESTIONS
Know the structure of the basic amino acid.
What is the difference in the 20 amino acids?
What does hydrophobic and hydrophilic mean?