Objectives Identify the structure and function of proteins.

Proteins Proteins have many structures, resulting in a wide range of function

Proteins ” Elements: C H O N Monomer: amino acids  (**They have nothing to do with acids or pH)

Amino acids 20 different kinds of amino acids Each amino acid has the same basic structure - central C - H atom - amino group - carboxyl group - “R” group (side group) “R” differs for each kind of amino acid

Building a Protein polypeptide a chain of amino acids joined together by peptide bonds protein one or more polypeptides joined together, folded and coiled into a 3D shape

Peptide Bond Formation (dehydration synthesis or hydrolysis?)

4 Levels of Protein Structure

Primary Structure Unique sequence of amino acids linked together to form a polymer Sequence different in every protein

Secondary Structure Primary structure is coiled and/or pleated Pleats and coils held in place by hydrogen bonds

Tertiary Structure Secondary structure is twisted and folded into a glob Each globular protein has a unique shape

Quaternary structure Two or more polypeptides linked together

Quaternary Structure Ex. Hemoglobin: an oxygen carrying protein in red blood cells which is made of 4 parts

Shape is also influenced by environment Usually proteins are in water Water attracts hydrophilic sides groups Water repels hydrophobic sides Hydrophilic amino acids orient toward outside edge of protein Hydrophobic amino acids cluster in the center

Function of a protein depends on the shape of the protein

Type 1: Structural Proteins (Secondary Structure) example: Keratin- used to make structures examples: hair, tendons, ligaments Type: Structural protein Example: fibroin- spider web "silk"

Type 2: Contractile Proteins Ex: Myosin - found in muscle cells

Type 3: Storage proteins(primary structure) Examples: albumin- egg white- stores food

Type 4: Defensive Proteins: used to fight invaders (ex. Globulin) Example: antibodies (neutralize antigens) What is an antigen? An antigen refers to any molecule or molecular fragments. Antigens are usually parts of proteins or polysaccharides (coats, capsules, cell walls, flagella, and toxins that flake off or are released from bacteria, viruses, and other microorganisms in the body) Non-microbial exogenous (foreign) antigens can include pollen, egg white, and proteins from transplanted tissues and organs or on the surface of transfused blood cells. Autoimmune disorders arise from the immune system reacting to its own antigens.

Type 5: Transport Proteins: move molecules (ex. Karyopherin) Example Proteins that help molecules enter and exit the cell

Type 6: Messenger proteins: carry messages from cell to cell Protein hormones  EXAMPLES:  Somatotropin- growth hormone (regulates bone, muscle and liver growth)  Leptin – adipose tissue (plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism)  Lutropin – pituitary (regulates production of estrogen and testosterone)

Type 7: ENZYMES catalyze (speed up) all reactions within the body We will learn MUCH more about this type of protein.

If a protein loses its shape, it loses its function. A protein that has lost its shape is said to be denatured.

Example of denaturation Frying an egg Egg white clear liquid changes to white solid the heat denatures the egg’s proteins. Process: Heat breaks the attractions between the side groups Protein then loses its shape and therefore its ability to work properly. s/content/proteinstructure.html

Can Acid Cook an Egg? An egg is largely protein and when you cook the egg you are actually denaturing the protein (that is a good thing) using heat. Vinegar, or lemon juice, makes the water acidic. Acid can penetrate the semi-permeable egg shell and denature the protein. It usually just denatures the protein on the outside and you heat your egg to denature the rest of the protein. The solid denatured protein prevents any other still liquid protein from escaping until you have finished cooking your egg.

Interesting Note If you let an egg sit in acid (more concentrated is better) such as vinegar or lemon juice, you can denature the entire egg without cooking it. It will also 'eat' the entire shell. the shell is largely calcium carbonate which will react with the acid to produce carbon dioxide and water.

Denaturizing What two ways can a protein be denatured?