Proteins

Proteins make up ~ _________% of the dry weight of cells. Serve diverse functions, such as structure (collagen, keratin), transport (hemoglobin), signals (hormones), movement (actin, myosin), defense (antibodies) and catalysts (enzymes)

A. ______________ acids are the monomers of proteins.

1. Basic structure of an amino acid: α carbon, amino group, carboxyl group, and an R (functional) group

2. There are 20 different amino acids that differ by R group (may be _________ , nonpolar, acidic, basic).

3. Amino acids are combined by dehydration synthesis into chains called polypeptides. The covalent bonds joining them are called ______________ bonds.

B. Protein structure is complex. The order of the amino acids that form the polypeptide affects how the protein folds together. The way that a polypeptide _________ to form the protein determines the protein’s function. Some proteins are comprised of more than one polypeptide.

C. There are ____________ general levels of protein structure: primary structure (1°), secondary structure (2°), tertiary structure (3°) and quaternary structure (4°).

1. Primary structure – the sequence of amino acids in the polypeptide chain. Dictated by a _____________ . This determines all other levels of protein structure.

2. Secondary structure – localized twisting/folding of polypeptide due to ________________ bonding, includes: α-helix and β-pleated sheet. The folded structure may resemble coils, helices, or sheets.

3. Tertiary structure – the final ________ shape of the protein ( functional protein) as a result of interaction among R groups (H bonds, ionic bonds, covalent bonds, hydrophilic/hydrophobic interactions). May be fibrous (collagen, keratin) or globular (like enzymes and hormones).