Chemical Structure of Proteins Nitrogen – Carbon – Carbon (NCC) Amino – Central & R - Carboxyl H N C R O OH Amino group Carboxyl (acid) group

Protein Structure Chain of amino acids (molecules) linked together like a necklace Each has its own unique structure of amino acids Some are polar others are non- polar

Protein Structure Twenty Amino Acids exist and we will study this chart when we learn how our body builds proteins Each has a different structure

Protein Structure (polypeptides) Proteins are often chains of polypeptides (smaller versions, 1-50 unites) Dipeptide formation dehydration

Dehydration/ Hydrolysis http://nhscience.lonestar.edu/biol/dehydrat /dehydrat.html

Protein Structure These long chains of amino acids fold into different structures

Protein Structure Primary structure (1*) = the sequence of amino acids Secondary structure (2*) = regular repeating shapes (a helix or B pleated sheets) due to H-bonding along the backbone of the protein. Tertiary structure (3*) = overall 3 dimensional shape mainly determined by interactions between R groups Quaternary structure (4*) = association of 2 or more polypeptide chains

Protein Function Varies Proteins play many important roles in the body (including muscle structure, hormones, antibodies, hemoglobin for carrying oxygen, other transport proteins for carrying molecules across cell membranes, toxins, and chemical messengers in the nervous system).

Enzymes: enable chemical reactions

Structural Proteins Examples: collagen in your skin, ligaments, tendons, and bones. Hair and muscles have structural proteins as well.

Movement: Actin and Myosin, cillia flagella

Transport Proteins

Communication: signal proteins

Defense: Antibodies

Motor Proteins: Within the cell

Intracellular junctions Extracellular matrix

Answer the following questions where you answered your Do Now: How many of the 20 amino acid molecules do you have in your set? Can you name three different functions performed by proteins in your body? Can you name some amino acids you have heard of before and indicate where you heard of them? Which of the CHNOPS elements are contained in all amino acids? In addition, two important amino acids, methionine and cysteine, also contain ____ and can be phosphorylated. To review, what is the major class of organic molecules described in this section? What are the subunits or building blocks of this class of molecules?