Proteins & Nucleic Acids• Proteins make up around 50% of the bodies dry mass and serve many

functions in the body including: – Enzymes – Biological catalysts that selectively speed up chemical reactions

• Decrease the energy of activation necessary to complete the rxn• Not used in the rxn but can be both activated & inactivated

– Storage – Defense against foreign substances – Structural components – Transport molecules – Movement – Cellular communications

Proteins• Proteins are made of one or more

polypeptides made from 20 amino acids. – All amino acids contain the same backbone

with amino and carboxyl side groups and differ only in their functional groups (-R).

– The carbon in the middle is called the a carbon. Attached to it is the a hydrogen atom and -R. • The side chains determine the individual

characteristics of an amino acid– Can be classified as polar, non-polar,

acidic or basic– 9 amino acids are considered to us… cannot be

synthesized from other amino acids

Peptide Bonds

• Bonds between amino acids are called peptide bonds and are formed via dehydration synthesis.– A union of many amino acids

forms a polypeptide• N-terminus attaches to the C-

terminus of the next molecule

Polypeptide Modification

• Once linked, the polypeptide starts to fold into its conformation (3D functional structure). This folding can be spontaneous or with the aid of an additional protein (chaperonins).– Although thousands of structures are possible, the

resulting structure is usually either globular (spherical) or fibrous.

4 levels of protein structure

• primary - sequence of amino acids • secondary - b pleat or a helix • tertiary - 3D structure aided by the

formation of H-bonds, Van der Waals interactions (hydrophobic attraction), & disulfide bridges (-S-S-)

• quaternary - 2 or more polypeptides wound into one macromolecule.

Alteration in Amino Acids (AA) or Conformation Inhibits Function

• AA addition, deletion, or substitution can render an AA dysfunctional– Sickle cell disease is caused by a single substitution in AA sequence

• Changes in temperature & or pH causes changes in the tertiary conformation of proteins causing the groove to not match the substrate– Process is called denaturation– Maintenance of these 2 values is called homeostasis

Nucleotides• Store and release transmit genetic

information• DNA (deoxyribonucleic acid) contains the

directions for all physiologic functions– Directs protein synthesis

• Gene is the basic unit of inheritance containing the instructions

– Self replicates• RNA (ribonucleic acid)

– Aids DNA in the functions of the cell

Nitrogenous Bases• Cytosine, Adenine, Guanine, Thymine, Uracil (C, A, T, G, & U)

– Each contains a nitrogenous base, pentose sugar. And a phosphate group

– 2 classes• Purines… A & G• Pyrimidines… C, T, & U

Assembly of the Polynucleotide• DNA & RNA is assembled by connecting the phosphate / sugar

backbone from 3’ carbon of one nucleotide to the 5’ carbon of the next– Phosphodiester linkage via dehydration synthesis– DNA forms a double a-helix protecting the nucleotides from mutation and

translation