Lecture 6: Proteins Flashcards

Vocabulary flashcards covering the key terms, protein functions, amino acid structures, four levels of protein structure, and cellular folding concepts from Lecture 6.

Proteins (Cell Mass)

Biological molecules that account for more than $50\%$ of the dry mass of most cells.

Enzymatic proteins

Proteins that selectively accelerate chemical reactions, serving as molecular catalysts such as digestive enzymes that catalyze the hydrolysis of bonds in food molecules.

Defensive proteins

Proteins that function in protection against disease, such as antibodies that inactivate and help destroy viruses and bacteria.

Transport proteins

Proteins responsible for the transport of substances, such as hemoglobin, the iron-containing protein of vertebrate blood that transports oxygen from the lungs to other parts of the body.

Storage proteins

Proteins that store amino acids, such as ovalbumin in egg white, which provides an amino acid source for the developing embryo.

Hormonal proteins

Proteins that coordinate an organism's activities, such as insulin, which is secreted by the pancreas to cause other tissues to take up glucose and regulate blood sugar concentration.

Receptor proteins

Proteins responsible for the response of a cell to chemical stimuli, such as receptors built into a nerve cell membrane that detect signaling molecules released by other nerve cells.

Contractile and motor proteins

Proteins that mediate movement, such as actin and myosin, which are responsible for muscle contraction.

Structural proteins

Proteins that provide structural support, such as collagen and elastin, which form a fibrous framework in animal connective tissues.

Amino acids

Organic molecules possessing both amino and carboxyl groups that serve as the monomers of proteins, differing in properties due to variable side chains called R groups.

Peptide bonds

Covalent bonds that link amino acids together to form polypeptides.

Polypeptide

A polymer of amino acids ranging from a few to more than a thousand monomers, characterized by a unique linear sequence with a carboxyl end (C-terminus) and an amino end (N-terminus).

Primary structure

The unique sequence of amino acids in a protein, determined by inherited genetic information.

Secondary structure

Coils and folds in a polypeptide chain resulting from hydrogen bonds between repeating constituents of the polypeptide backbone, typically forming an alpha helix or a beta pleated sheet.

Alpha helix

A typical coiled secondary structure held together by hydrogen bonds in the polypeptide backbone.

Beta pleated sheet

A typical folded secondary structure formed by hydrogen bonding in the polypeptide backbone.

Tertiary structure

The overall three-dimensional shape of a protein determined by interactions among side chains (R groups), including hydrogen bonds, ionic bonds, hydrophobic interactions, Van der Waals interactions, and disulfide bridges.

Disulfide bridges

Strong covalent bonds between side chains that reinforce a protein's tertiary structure.

Quaternary structure

The structural level that results when two or more polypeptide chains combine to form a functional protein, such as hemoglobin (four polypeptides) or collagen (three coiled polypeptides).

Sickle-cell disease

An inherited blood disorder resulting from a single amino acid substitution in the protein hemoglobin, demonstrating the effect of primary structure alterations.

Denaturation

The unraveling and loss of a protein's native structure caused by environmental factors like alterations in pH, salt concentration, or temperature, rendering the protein biologically inactive.

Chaperonins

Protein molecules that assist in the proper folding of other proteins within the cell.