Protein Structure and Examples

Types of Proteins Structural Proteins: structure and support for cells, tissues, and organs. ex. actin, keratin Enzymes: facilitate nearly all chemical reactions within cells. ex. lactase, RNA polymerase Antibodies: bind with bacteria and other pathogens to protect the body from infection. ex. immunoglobulin Messengers: water-soluble hormones that allow different cells, tissues and organs to communicate with each other. ex. growth hormone, insulin Transport Proteins: bind and carry atoms and molecules to transport within cells and around body. ex. hemoglobin Storage Proteins: store molecules for use by the cell. ex. ferritin

Protein Folding: Primary Structure Proteins (polypeptides) are composed of amino acids connected by peptide bonds The primary (1°) structure of proteins is a chain of amino acids. Proteins are not functional in their primary structure.

Protein Folding: Secondary Structure The secondary (2°) structure of proteins is seen when the side chains (R groups) of neighboring amino acids begin to form hydrogen bonds with one another. Some proteins are functional when in their secondary structure. alpha(α) helix: ex. keratin (structural protein in hair) beta(β)sheet: ex. fibroin (structural protein in silk)

amino acid

Protein Folding: Tertiary Structure The tertiary (3°) structure of proteins is seen when the side chains (R groups) form bonds with other R groups that force the alpha helix or beta sheets to fold into a globular shape. Some proteins are functional when in their tertiary shape. Specific amino acids in certain locations form the active sites of enzymes.

Protein Folding: R groups Strong interactions: disulfide bridges: form between cysteine amino acids Weak interactions: hydrophilic: polar R groups form hydrogen bonds ionic bonds: between charged R groups hydrophobic: nonpolar R groups arrange to be protected from water

Protein Folding: Quaternary Structure The quaternary (4°) structure of proteins is seen when multiple amino acid chains combine to form one protein. Some proteins are only functional when in their quaternary structure. This includes collagen, insulin, and hemoglobin.

Protein Folding: Hemoglobin Hemoglobin is the protein that is responsible for carrying oxygen & CO2 in red blood cells. Red blood cells eject their nuclei after formation, so they are essentially a membrane- bound packet filled with hemoglobin. The iron in the heme group binds with oxygen. Iron deficient anemia is when the lack of iron in the blood reduces the amount of oxygen that can be carried by the blood.

Protein Folding: Hemoglobin mutation Sickle-cell anemia is a genetic disorder that arises from a single nucleotide mutation in each hemoglobin subunit. The mutation leads to a change in one amino acid. This change in one amino acid gives the hemoglobin subunits a larger hydrophobic area. These hydrophobic areas group together to avoid water, leading to long chains of hemoglobin proteins joined together. This causes the red blood cell to fold into a sickled shape. These cells can get caught in capillaries, blocking blood flow.

https://www. boundless https://www.boundless.com/biology/textbooks/boundles s-biology-textbook/biological-macromolecules- 3/proteins-56/types-and-functions-of-proteins-302-11435/ http://higheredbcs.wiley.com/legacy/college/tortora/04 70565101/hearthis_ill/pap13e_ch19_illustr_audio_mp3_am /simulations/hear/rbc.html http://www.austincc.edu/emeyerth/tertiary.htm