PROTEINS Biological Structure and Function Objectives 1 Describe

PROTEINS Biological Structure and Function Objectives 1. Describe the structure (state the functional groups) and function of proteins 2. Explain what an amino acid is and their role in protein formation. 3. Explain what denaturation is and what conditions can cause this to happen.

Protiens – The Workhorses of the Cell! � � most cellular structures are made of proteins The main functions of protein are: � ENZYMES (biological catalysts) catalyze almost every reaction in living organisms � STRUCTURE e. g. kertin in feathers e. g. collagen in cartilage and tendons � � TRANSPORT across membranes CHEMICAL MESSENGERS (hormones) e. g. insulin

Subunits or Building Blocks � building blocks of proteins are AMINO ACIDS � there are 20 different amino acids each amino acid has a different R group �

20 different amino acid s

Diet… 20 essential amino acids • your body can make most of the amino acids but 8 amino acids must be consumed • if you eat meat, you will get all 8 essential amino acids • grains (corn, rice, wheat etc. ) contain some of the 8 • beans + grains will provide all 8 essential amino acids � � So…. if you are a vegetarian/vegan, you MUST eat beans and grains together!!!

Proteins… � Proteins differ from each other by the number and sequence of amino acids that compose them � most proteins are composed of 100’s or 1000’s of amino acids

Putting the subunits together… � � � a reaction occurs between the carboxyl group of one amino acid and the amino group of the second amino acid water is removed and the amino acids are joined by a peptide bond a small chain of amino acids is called a polypeptide

Protein Synthesis � � � cells make proteins by joining amino acids together as the chain of amino acids lengthen the R groups begin to interact… some repel each other, some attract each other regions the polypeptide wrap into coils or fold into sheets eventually the entire protein folds into a 3 D shape

Final Shape and Function � � � proteins with the same amino acid sequence will fold into the same shape if the correct 3 D shape is not formed, the protein will not work properly the proper shape may be changed by a mistake in just one amino acid

How does the shape effect function? � � if there are lots of folded sheets in the protein, the protein forms strong fibers (e. g. keratin, spider silk) if there are lots of coils, the protein forms flexible “globular” proteins (e. g. hemoglobin)

DENATURATION � � � Denaturation is a change in the 3 D shape of a protein caused by changes in the environmental conditions A denatured protein can not refold (even if returned to proper conditions) and can not perform its function proteins can unfold if they are exposed to � high temperatures (usually above 40°C) � very acidic or basic conditions

Denaturation …. Good or Bad? � Bad… � High fevers (over 39°) may cause important enzymes in the brain to denature → seizures, death � Good… � curing meat, pickling vegetables denatures enzymes in the bacteria that would otherwise spoil the food � cooking meat denatures proteins which soften the meat and make it easier to chew

Your Task � � Read pp. 30 -33 Answer Questions #5 -8 on pp. 35