By Isabel DesRoches, Kylie Gallagher, Adam Ober, Katie Sauer, & Amanda St Germain

4 levels:
Primary
Secondary
Tertiary
Quaternary
Structure is determined by specific amino acid sequences.
Denaturation - when a protein unravels and loses its shape, and thus deactivates.
Caused by change in type of environment, high temp., high pH

amino acids sequence together specified by a gene determines secondary and tertiary structure chemical nature of backbone and R groups of amino acids dictate structure of the whole protein

results from interactions along backbone oxygen on backbone have a (-) charge hydrogen attached to nitrogen have (+) charge hydrogen bonds form between the repeating parts of the polypeptide backbone

results from interactions between R groups hydrophobic interaction hydrophobic chains fold into clusters at core of protein held together by van der Waals interaction all bonds used (hydrogen, ionic, van der Waals) are weak on their own in aqueous environment work together to give protein a

2 or more polypeptide chains aggregate into a single macromolecule

sickle cell disease - (The Hemaglobin Protein Subunit Beta-Globin is abnormal and called hemoglobin S) hemoglobin molecules are deformed and clog blood vessels and organs.
cystic fibrosis - (The majority of cases result from mutated genes failing to order the production of phenylalanine.) sticky mucous builds up in lungs and intestines.
muscular dystrophy - (the exclusion of several amino acids causes defective dystrophin to form) improper muscle action.

Monomers of proteins are called amino acids
Amino acids are made of 5 parts:
1.A central carbon (alpha carbon)
2.A hydrogen atom
3.An amino group
4.A carboxyl group (acid group)
5.An R-Group (side chain)

R Groups (side chains)
● There are 20 different R-groups = 20 different amino acids
○ Each individual R-group has special properties that determine the properties of the protein
● Are either nonpolar (hydrophobic), polar (hydrophilic), or electrically charged (hydrophilic)
● Human body can make 11 of the total 20 amino acids
○ Other 9 amino acids must be obtained from food

Though there are 4 levels of structure in proteins (Primary,
Secondary, Tertiary, and
Quarternary)the Protien
Polymer at its most basic is seen in the primary structure as a chain of amino acids.

Protein Polymers:
Polymer : a long molecule formed by many similar or identical monomers covalently bonded to one another.
-Amino acids are the monomer "building blocks" of the protein polymer (there are 20 common amino acids and a few other rarer ones)
-The order in which the amino acids line up in the polymer chain determines the function of the protein
-Oftentimes, the amino acids bend and twist the chain when attached, it is this that forms the features of the second tertiary level like alpha helixes (corkscrew-like structures) and beta pleated sheets (which are often ridged but overall staight sections of the chain)
-The combination of all of the alpha helixes and beta pleated sheets further assist the protein in its function and is known as the tertiary level
-Multiple tertiary structure chains may combine to form a large Quarternary structure protein, the highest level
-Everything about this high level protein molecule is determined by the order and behavior of the amino acids in the chain
-The constant dependency of the lowest level (primary structure) of the protein polymer is missing even a single amino acid it can lead to huge problems with the proteins functions and formation

There are a few types of bonds that can form between the monomers (amino acids) of proteins. These bonds help to determine the structure of the protein as well as its function.
1. Peptide Bond
2. Hydrogen Bond
3. Ionic Bond
4. Covalent Bonds (Disulfide
Bridges)

Peptide Bonds :
● 2 amino acid molecules present
● molecules oriented so that the carboxylic acid group of one molecule can react with the amine group of the other
● peptide bond forms with elimination of water molecule through dehydration synthesis
● formation of a dipeptide
Ionic Bonds :
● can form if some of amino acids in proteins have carboxylic acid or amine side groups
● ionic bonds between positively and negatively charged side chains help stabilize tertiary structure
Hydrogen Bonds :
● forms in all proteins
● hydrogen atom of one peptide link attracted to oxygen of another peptide link
● hydrogen bonds between polar side chains help stabilize tertiary structure
Covalent Bonds (Disulfide Bridges) :
● further reinforces shape of a protein
● form when 2 cysteine monomers, which have sulfhydryl groups (-SH) on their side chains are brought close together by protein folding
● sulfur of 1 cysteine bonds to the sulfur of another and disulfide bridge (-S-S) rivets parts of the protein together
● help to stabilize tertiary structure

Proteins different structures cause a variety of different functions.
Eight Major Functions
Enzymatic Proteins
Defensive Proteins
Storage Proteins
Transport Proteins
Hormonal Proteins
Receptor Proteins
Motor and Contractile Proteins
Structural Proteins

● Speed up chemical reactions
● Enzymes use less energy
● Can be used again and again
Example: Digestive enzymes speed up breaking down food molecules.
Defensive Proteins
Protects from disease
Example: Antibodies protect from viruses and bacteria by killing them

Store amino acids
Example: Ovalbumin is a protein in eggs whites and stores amino acids and then provides them for the developing embryo
Transport Proteins
Hemoglobin
Transports a variety of substances
Examples:
Hemoglobin is an important protein that allows oxygen to get from the lungs to other body parts by transporting the oxygen.
Transport proteins are apart of the cell membrane and allows substances to cross the membrane that could not move across the membrane because of charge or size. Creates facilitated diffusion and active transport.

Involved in the coordination of activities
Example: Insulin is a protein that is released to cause tissue to intake glucose. This causes blood glucose levels to remain constant
Receptor Proteins
Responds to chemical stimuli
Can create a signal transduction pathway in a cell membrane
Example: Receptor Proteins in cell membranes, specifically in never cells, receive signaling molecules from other cells.

Responsible for movement
Example: The proteins actin and myosin create relaxation and contracting in muscles to allow for movement
Structural Proteins
Provides support
Examples:
Keratin forms hair, and feathers
Collagen forms connective tissue
Holds cells together, Intercellular joining Collagen

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