Review of Biological Chemistry

Biologically Important Elements

Carbon All organiccompounds

Hydrogen Organic compounds

Oxygen Terminal electronacceptor;Carbohydrates, lipids

Nitrogen Proteins

Sulfur Protein tertiarystructure

Phosphorus Nucleic acids;Phospholipids; ATP

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: Cx(H2O)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