Proteins

Proteins perform most functions in cells.

Characteristics of Proteins Contain carbon, hydrogen, oxygen, nitrogen, and sulfur Amino acids (monomers) are the basic building blocks of polypeptides (polymers) and polypeptides form proteins. Functions: structural components of cells catalyzing chemical reactions (enzymes) transporting substances within cells messenger molecules (hormones)

Question Which of the following pairs of terms is INCORRECTLY matched? fatty acid – steroid monomer – polymer amino acid – protein monosaccharide – polysaccharide Lipids such as fatty acids and steroids are the only group of biological macromolecules that do not consist of monomers joined together to form polymers.

Amino Acids 20 different types found in organisms – same basic structure. Amino group acts like a base, tends to be positive. Carboxyl group acts like an acid, tends to be negative. “R” group is different for each amino acid (varying in size from 1-20 atoms).

Question 20 How many different types of amino acids are found in living things? (numeric response)

Some Amino Acids

Some More Amino Acids

Still More Amino Acids

Peptide Bonds Adjacent carboxyl and amino groups covalently bond together, forming a peptide bond. Two amino acids join together to form a dipeptide. A chain of amino acids is called a polypeptide.

Question What type of reaction is shown in this diagram illustrating the formation of a peptide bond? Hydrolysis Precipitation Double replacement Dehydration synthesis Notice the removal of water required to form the bond.

Shape = Function A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape. The shape of a protein determines its function. Hemoglobin is an iron-containing protein in red blood cells that carries oxygen for delivery to cells. It consists of four polypeptides that fit together to form the final shape of the protein. Oxygen molecules bind to the iron portion (also called the heme group) of the hemoglobin molecule.

Denaturation loss of normal shape of a protein due to heat or other factor

Levels of Protein Structure

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