Protein

PROTEINSDoris LeeEven ZhengJoanna TangKiki JangRachel ZhangVincent MaWhat are the functions of proteins?Proteins, one of the most important biological molecules in our body. They are included in virtually all of the cell functions.

There are numerous of proteins; they are not only different in functions but also vary in their structure.

Antibodies- are proteins that are specialized to defend our body from antigensContractile Proteins- are responsible for movement.

Enzymes- are catalysts that speed up the biological reactions.Hormonal Proteins- are messenger proteins which help to coordinate certain bodily activities.Structural Proteins- are fibers that provide support.

Storage Proteins- are used to store amino acids.Transport Proteins- are carrier proteins that circulate other molecule around the body.

What are Proteins Made of?proteins are made up of amino acids amino acids link together to form polymers = proteins

Structure of Amino AcidAmino acids are made up of an amino group (-NH2) and a carboxylic acid group (-COOH), distinguished by the attached functional group R.The key elements of amino acids are Carbon, Hydrogen, Oxygen and Nitrogen.The most common amino acid is shown above, with a carbon atom attached to the carboxyl group, called an alpha amino acid.

Amino acids have properties of both acids and bases. The amino group gives the amino acids its basic properties and the carboxyl group gives amino acids its acidic properties.R represents a group called a side chain which varies from one amino acid to another. It distinguishes an amino acid as a weak acid or a weak base, and a hydrophile if the side-chain is polar or a hydrophobe if it is non-polar.

What is a Peptide bond?http://www.mrothery.co.uk/images/Image46.gif

Peptide bond is a covalent bond that joins 2 amino acidEx. A polypeptide is a string of amino acids joined by peptide bonds A dipeptide results when 2 amino acids join and also forms water as a by product

dipeptide formation

The differences between primary, secondary, tertiary, and quaternary structure

Primary StructureComposed of amino acids polypeptide chainsa slight change in the structure can effect the appearance and function of the proteinex. Blood cell sickled cell

Secondary Structureis made up of repeated coils and folds of polypeptide chainsresult of hydrogen bonds at regular intervals along polypeptide backbonetwo types: helix pleated sheet

Tertiary Structuresuperimposed on the patterns of secondary structurescontortion caused by the interaction in side chains of amino acids

2 types of interactionshydrophobic: clustering of hydrophobic group away from waterVan de Waals: weak bonds between side chains that hold the protein in a specific conformationthe appearance of the structure can be reinforced by a covalent bond called disulfide bridges

Quaternary Structureresult from the aggregation of polypeptide subunitsmade up of primary, secondary, and tertiary structures

DifferencesPrimary Structure is a sequence of amino acids (line)Secondary Structure is pleated sheet or helix (flat and 2D)

Tertiary structure is 3DQuaternary is more complicated, combined with different protein structures

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