Proteins and Nucleic Acids

Proteins

Macromolecules made up of amino acids that perform a variety of functions in cells, including structural support, storage of amino acids, cell signaling, movement, defense against infection, catalysis of chemical reactions, and more.

Amino Acids

Organic compounds that make up proteins. They consist of a carbon atom bonded to a hydrogen atom, a carboxyl group, an amino group, and an R-group. There are 20 different used in human cells, 11 of which are synthesized metabolically and 9 of which must be obtained through the diet.

R-group

amino acid variants that bond to carbon atom of protein molecule

Non-polar amino acid

r-group does not contain oxygen or nitrogen, less soluble in water

Polar amino acid

R-groups contain oxygen and nitrogen (hydroxyl, amide), more soluble in water. Sulphur is slightly more electronegative than hydrogen so Cysteine is also considered polar, but weakly

Charged amino acid

amino acid with carboxyl or amino group at end of R-group will ionize. Acidic are negatively charged (carboxyl ionizes to give up H+) Basics are positively charged (ionizes by taking up H+)

Polypeptides

chain of amino acids linked together by peptide bonds. Addition of new amino acid to carboxyl end called condensation.

Primary Structure

The specific sequence of amino acids in a protein. Even small changes to it can disrupt a protein's function.

Secondary Structure

The folding or coiling of a polypeptide chain due to hydrogen bonding between amino acids. Common structures include alpha helices (single polypeptide) and beta sheets (two lying in parallel)

Tertiary Structure

The three-dimensional shape of a protein, which is determined by interactions between amino acid side chains. Essential for a protein's function. Weak interactions: hydrophobic interactions, H-bonds, Ionic bonds, covalent bonds, disulfide bridges)

Quaternary Structure

The arrangement of multiple polypeptide chains in a protein. Proteins with this structure consist of two or more subunits that must be folded properly. (e.g. hemoglobin)

Denaturation

The process by which a protein loses its shape and function due to changes in its environment, such as high temperature or extreme pH.

Nucleic Acids

Biomolecules that store and transmit genetic information for proteins. (e.g. DNA and RNA)

DNA

double-stranded molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms. It consists of nucleotides, which are composed of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases.

Purine

Dicyclic ring structure (e.g Adenine, Guanine)

Pyramidine

Monocyclic ring structure (e.g. Cytosine, Thymosin, Uracil)

Phosphodiester linkage

A chemical bond connecting nucleotides. It forms between the phosphate group of one nucleotide and the sugar molecule of another nucleotide.

RNA

Single-stranded molecule, key role in the synthesis of proteins. Contains the sugar ribose and the base uracil instead of thymine.