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

2. 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

3. 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

4. 20 different amino acids

5. 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 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!!!

6. 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

7. 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

8. 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 3D shape

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

10. 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)

11. DENATURATION
Denaturation is a change in the 3D 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

12. Denaturation …. Good or 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

13. Your Task
Read pp
Answer Questions #5-8 on pp. 35