Structure and Function of Amino Acids Introduction

Hi guys and gals, this is a summary of my notes on Amino Acids, it should give you a run down on the basics and skip over any of the stuff you dont REALLY Need to know to have a vague understanding.  If this isnt really to your taste let me know. 🙂 

 Amino Acid

Proteins are composed of 20 different amino acids, in each protein the amino acids are arranged in a specific sequence that determines the characteristics and the function within the body of the protein.

Essential Amino Acids

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phennylalanine
  • Threonine
  • Tryptophan
  • Valine
  • Arginine

Complete proteins, such as eggs, milk, fish and meat contain all of the essential amino acids. Plants, Grains, beans and nuts are deficient in one or more essential amino acid. The MUST be obtained from the diet, as there are 10 amino acids not synthesised by the body. A complete protein will contain all 10. By combining legumes and grains a complete protein is made as each missed what the other has.

Protein = Macromolecule that contains: Carbon, Hydrogen, Oxygen and Nitrogen: all needed by the body for growth, repair and to make up enzymes: a polymer made of amino acids

Food Source Amino Acid Missing
Egg, Milk, Fish, Meat and Poultry NONE
Wheat, Rice and Oats Lysine
Corn Lysine and Tryptophan
Beans Methionine and Tryptophan
Peas Methionine
Almonds and Walnuts Lysine and Tryptophan
Soy Low in Methionine


Classification of a Protein according to its Class and Function

Structure Determines Function.

Class Function Examples
Structural Provides structural components Collagen in tendons and cartilage
Contractile Makes muscles move Myosin and actin – contract muscle fibers
Transport Carry essential substances around body Hemoglobin takes oxygen around the body
Storage Able to store nutrients Casein stores the protein in milk
Hormonal Regulates metabolism and  the nervous system Insulin regulates blood glucose levels
Enzyme Catalyse biochemical reactions in the cell Sucrase catalyse the hydrolysis of sucrose
Protection Recognise and destroy foreign substances Immunoglobin stimulates the immune response


General Structure of Amino Acids

Amino Acids are the building blocks of proteins

  • They contain a Carboxylic Acid group and an amino group on the Alfa Carbon
  • They are ionized in a solution  – undergo an internal based reaction
  • Each contain a different side group (R)
  • Amino, Carboxylic, Hydrogen and Carbon: R side chain is dissolvable in aqueous solution

Types of Amino Acids

  • Non Polar (Has no PH) (Hydrophobic) – Hydrocarbon side chains CH3
  • Polar (Hydrophilic) –Polar or Ionic side chains CH2 – OH
  • Acidic (soluble in water) (Hydrophilic) with an acidic side chain
    C –O-
    =O (acids in aqueous solutions release hydrogen)
  • Basic (soluble in water)(Hydrophillic) with NH2 side chains
  • Sulphur containing



Non Polar Amino Acids

  • Has an R group that is H, an Alkyl group or aromatic (H can be replaced by a benzein ring sometimes)

Polar Amino Acids

  • Has an R group that is an alcohol, Thiol or amide (up to five amides are water soluble)

Acidic and Basic Amino Acids

  • An amino acid is acidic with a carboxylic R group COO-
  • An amino acid is basic with an amino R group NH3+

Fischer Projections of Amino Acids

  • Amino Acids are chiral except for glycine
  • Amino Acids have Fischer Projections that are stereoisomers
  • Amino Acids that are L are used in Protiens (Mostly L acids are what the body uses)

Amino Acids and Zwitterion

A Zwitterion

  • Has charged –NH3+  and COO- Groups
  • Forms when both –NH2+  and –COOH groups in an amino acid ionize in water
  • Has equal + and – charges at the isoelectric point (pl)

Buffering Abilities of Amino Acids

Release or accept of hydrogen ion. In solutions more basic than pl, the -NH3+ in the amino acid donates a proton. And in solution more acidic than the pl, The COO- in the amino acid accepts a proton.

As Acids = release hydrogen in water environments.

As Base = accept hydrogen in acidic solution.


The properties of Amino Acid – Cysteine

The amino acid, Cysteine, contains sulphur – eg Hair.


A peptide bond is an amide bond, formed between a carboxylic group of one amino acid and the amino group of the next amino acid.

Peptide refers to Protein; short protein, up to 50 amino acids. Polypeptides are much larger.

Dipeptide Formation: two amino acids link to peptide . During Synthesis water is removed : called Dehydration Synthesis.


Electrophoresis : Separation of Amino Acids

In electrophoresis an electrical current is used to separate the mixture of amino acids.

  • Positively charged amino acids move towards the negative  electrode.
  • Negatively charged amino acids move towards the positive electrode.
  • An amino acid at pl does not move
  • The amino acids are identified as separate bands on the filter paper

3 thoughts on “Structure and Function of Amino Acids Introduction

  1. Pingback: Proteins, The Structure and Function, An Introduction | Elysium Tewlder

  2. Hello you have a fantastic blog over here! Thanks for posting this interesting stuff for us! If you keep up the good work I’ll visit your site again. Thanks!

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