Proteins – V2

Proteins - Functions Food sources for proteins are nuts, meat, fish, milk, and beans. Four main functions: Major structural component of all cells, organs and tissues Enzymes that speed up all chemical reactions are all proteins Transport substances within and between cells Chemical messengers and protein based hormones

Proteins - Monomers All proteins are made of the same 20 amino acids connected in different combinations. Ten amino acids are considered essential in the diet of adult humans and our bodies can make the remaining 10 from the amino acids that we eat. Infants and children need more amino acids because their bodies cannot make as many.

TWENTY AMINO ACIDS All amino acids have a nitrogen functional group, an acid functional group and a side functional group that makes each amino acid unique.

Proteins – Forming Polypeptides Amino acids bond by dehydration synthesis between the amino and acid functional groups of two amino acids. This forms a covalent peptide bond. Polypeptides have from 40 to 1000 amino acids in a long chain.

Protein Folding and Structures Proteins are only functional when the polypeptide folds into the correct 3D shape. A polypeptide is a primary protein structure. The secondary protein structure involves forming hydrogen bonds  helix folds forming a spiral  pleated folds forming sheets

More Protein Folding A tertiary protein folding occurs to make an active protein. The tertiary structure is a complex shape. Bonds are formed between the functional groups on the different amino acids. Sulfhydryl functional groups form strong covalent bonds called disulphide bridges. Some R groups are hydrophilic and will be on the outside of the protein, hydrophobic groups will be inside the protein, and cations attract anions.

Even More Protein Folding Often a tertiary protein is complete and works. Sometimes two or more tertiary proteins bind to form a quaternary protein like hemoglobin. Hemoglobin has two alpha and two beta chains all joined together. Each of the tertiary proteins has one iron atom that binds to oxygen.

Hemoglobin – A Quaternary Protein made from 4 tertiary proteins

Remember the 4 functions of proteins? Here is an example of each. 1. Keratin – Structural Protein in hair

2. Lactase – Enzyme Protein

3. YiiP Transporter Protein for Zn and Ca - found in E 3. YiiP Transporter Protein for Zn and Ca - found in E. coli cell membranes

4. Insulin – A Chemical Messenger The left side is a space-filling model of the insulin monomer. On the right side is a ribbon diagram of the insulin hexamer, thought to be the stored form. A monomer unit is highlighted with the A chain in blue and the B chain in cyan. Yellow denotes disulfide bonds, and magenta spheres are zinc ions.