Organic MoleculesPart 2

Lipids and Nucleic Acids

Objectives

• Relate the structure of lipids to their function.

• List two essential functions of nucleic acids.

Lipids

• Lipids are large, non-polar organic molecules.

• They do not dissolve in water.

• Store energy efficiently.

• Large number of Carbon-hydrogen bonds (store more energy than Carbon-oxygen bonds)

Lipid Monomer• Fatty Acids

• Unbranched carbon chains that make up most fatty acids.

• One end is a straight carbon chain (12-28 C) the other is a carboxyl group (-COOH)

• Carboxyl end is polar, and "water loving" - hydrophilic

• Hydrocarbon end is non-polar, and "water fearing" - hydrophobic

Saturated Fatty Acids

• Each Carbon atom is covalently bonded to 4 atoms.

• Carbon atoms are "full" or saturated.

Unsaturated Fatty Acids

• Carbon atoms are not bonded to the maximum number of atoms.

• Double bonds within the Carbon chain.

Lipid Polymers

• Divided into 3 categories based on their structure.

• Three classes contain fatty acids: Triglycerides, phospholipids, and waxes.

Triglycerides• Composed of three fatty

acid molecules joined to one molecule of the alcohol glycerol.

• Saturated -high melting points, solid at room temperature

• Shortening and animal fats

• Unsaturated -liquid at room temperature

• Found in plant seeds and fruits

Phospholipids

• Two fatty acids joined to a molecule of glycerol

• Makes up cellular (plasma) membrane (Lipid Bilayer)

• Creates a barrier between inside and outside of cell.

Wax• A type of structural lipid.

• A long fatty acid chain joined to a long alcohol chain.

• Highly waterproof.

• Forms a protective coating on plants.

• Protective layers in animals (earwax, beeswax, spermaceti, lanolin)

Steroids• Not composed of

fatty acids.

• Made of 4 Carbon rings with various functional groups.

• Many animal hormones are steroid compounds.

• Testosterone

• Cholesterol

Nucleic Acids• Very large and

complex organic molecules

• Store important genetic information.

• Information can be passed from parent to offspring

• DNA and RNA

Nucleic Acid Monomers

• Nucleotides

• Made of three parts

• Phosphate group

• Five-Carbon sugar

• Nitrogen-containing base

DNA• Deoxyribonucleic Acid

• Stores information in the nucleus of the cell

• Sugar is deoxyribose

• Double helix (two strands)

RNA• Ribonucleic Acid

• Carries information out of the nucleus to make protein

• Sugar is ribose

• Single strand

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