Download Atoms, Molecules & Life

Proteins

One of the most important organic molecules

Almost 50% dry weight of cells

Composed of monomers known as amino acids

Contains hydrogen, carbon, oxygen and nitrogen
and a variable side chain (R)
+
R
H3N – C – COOH

Amino acids link together to form a polypeptide

Amino acids link together to form a polypeptide

Linear arrangement of different amino acids is
known as its primary structure

Amino acids link together to form a polypeptide

Linear arrangement of different amino acids is
known as its primary structure
Because of chemical bonding and repulsion, the
linear arrangement of amino acids begins to fold
taking on one of two distinct shape:
Alpha helix
Beta pleated sheet
Less common Random coil


When the polypeptide folds into a threedimensional shape, it is called a protein

The three-dimensional shape of a protein is called
its tertiary structure
Myoglobin
 Binds oxygen
 Found in the muscles
 Acts as a storage site
for oxygen
 Makes up the dark meat in
chicken

If two or more polypeptide chains link to form a
protein its called it quaternary structure
Hemoglobin
 Binds oxygen in the lungs
and transports it through
out the body
 Helps to regulate blood
pressure

Shape of the protein is important for its function
Ex. Insulin = 51 amino acids

Shape of the protein is important for its function
Ex. Insulin = 51 amino acids
Types of Proteins
Type
Function
Communication
Cell signaling
Ex. Hormones in the bloodstream
Defense
Protection from infection
Ex. Antibodies in the bloodstream
Structure
Mechanical support
Ex. Collagen in skin & keratin in hair/nails
Storage
Stores nutrients
Ex. Albumin in egg whites
Contractile
Movement
Ex. Actin and myosin in muscles
Transport
Carries other molecules
Ex. Hemoglobin
Hormones
Chemical messengers
Ex. Growth hormone stimulates bone growth
Enzymes
Speed up chemical reactions
Ex. Catalase
Just for fun facts:
Your hair is composed of all -helix
Spider webs are all -pleated sheets