Review of Biological Chemistry

Biologically Important Elements

Chemical Bonds Covalent –Sharing of electrons –Strong bonds –Multiple bonds possible (especially with carbon) Single Double Triple Ionic –Transfer of electrons and attraction of resulting ions –Relatively weak; tend to dissociate

Hydrogen Bonds Attraction between portions of different molecules with partial charges Water molecules Important in the structure of proteins

Macromolecules in Cells Carbohydrates Lipids Proteins Nucleic Acids Note: Most of the cell is water

Carbohydrates Composed of carbon, hydrogen and oxygen General formula: C x (H 2 O) y Polymers of simple sugars such as glucose Storage of energy and structural compounds

Linkages Between Sugars: Alpha

Linkages Between Sugars: Beta

Lipids Chemically diverse group of chemicals Defined on the basis of hydrophobicity -- lipids do not dissolve in water. Include fatty acids, fats, and waxes Major structural components of membranes -- phospholipids

Phospholipids and Membranes Lipid with attached phosphate group Hydrophilic head with hydrophobic tail When placed in water orient with lipids on inside and phosphates facing the water -- bilayer or membrane

Proteins Function as enzymes and structural components of cells/organisms Polymer of amino acids Multiple levels of molecular organization –Primary structure –Secondary –Tertiary –Quaternary

Amino Acids Central carbon atom with attached –Amino group –Carboxylic acid group –“R” substitution group/side chain –Hydrogen

Peptide Bonds Two amino acids become linked by a hydrolytic reaction between the amino group on one and the acid group on the other. Note: this leaves a free amino and acid group for additional bonds.

Levels of Protein Structure Primary structure –Linear sequence of amino acids –Ultimately this determines all other levels of structure Secondary structure –Folding of the amino acid chain into repeating structures -- alpha helix and pleated sheets

Secondary Structure

Tertiary structure –Folding into a globular form due to intramolecular interactions Hydrogen bonds Ionic interactions Sulfur bridges Hydrophobic interactions

Quaternary Structure Some proteins are made of multiple protein chains which associate Example hemoglobin

Nucleic Acids DNA –Deoxyribonucleic acid –Carries all the genetic information of the organism RNA –Ribonucleic acid –Transfer of information from DNA to proteins

Components of Nucleic Acids Phosphates Sugar –RNA: ribose –DNA: deoxyribose Bases –Purines –Pyrimidines