Biological Macromolecules A.Carbohydrates B.Lipids C.Proteins D.Nucleic acids

A.Carbohydrates General properties –Composed mostly of carbon, hydrogen, and oxygen –Large number of –OH groups attached to the carbons –Functions Energy source for living cells Certain structural components of cells

Monosaccharides –“Simple sugars” –Monomer unit of carbohydrate group –Examples: glucose, fructose Disaccharides –Composed of two monosaccharide units joined together –Examples: sucrose, lactose Polysaccharides –Composed of multiple monosaccharide units (100s – 1000s) –Examples: starch, glycogen, cellulose A. Carbohydrates

General properties –Biological compounds with hydrophobic components in their molecular structures –Functions Energy storage Structural components Glycerides –A major class of lipid –Composed of a glycerol molecule attached to one, two, or three fatty acid molecules B.Lipids

–Generalized structure of a triglyceride: B.Lipids

Fatty acid saturation –Fatty acids with greater saturation have fewer C=C double bonds; Have higher melting points –Fatty acids with less saturation have more C=C double bonds; Have lower melting points

B. Lipids Phospholipids –A lipid molecule (for example, a diglyceride) with a hydrophilic group attached via a phosphate linkage –Found in membrane structure (details later in course) Other lipids –Sterols: cholesterol and steroid hormones –Waxes

General properties –Composed of chains of amino acids –There are 20 different amino acids, each with distinctive chemical properties –A protein molecule may contain several hundred amino acids –Each different protein has its own order, or “sequence,” of amino acids –The correct sequence of amino acids is essential for the protein’s function C.Proteins

Functions –Enzymes: enzymes are biological catalysts that control almost every reaction in living systems –Cellular recognition and communication –Structural components of living cells C.Proteins

Amino acid structure –To the central carbon atom, four things are attached: Hydrogen atom Amino group Carboxylic acid group Side chain “R” group –Twenty different “R” groups, with different chemical properties C.Proteins

Peptides –Chains of amino acids attached by peptide bonds –May be named by number of amino acids: dipeptide, tripeptide, tetrapeptide, pentapeptide, etc.; Polypeptide C.Proteins

Protein: –A polypeptide chain with a specific biological function –Most proteins have from about 50 up to several hundred amino acids in their structure C.Proteins

Levels of protein structure –Primary structure: amino acid sequence –Secondary structure: localized folding of a chain into regions of helix or sheet structure –Tertiary structure: folding of a single polypeptide chain into a three-dimensional structure –Quaternary structure: only in proteins with more than one polypeptide chain; Folding of more than one chain together C.Proteins

General properties –Composed of chains of nucleotides –There are 4 different nucleotides –A nucleic acid molecule may contain several thousands or millions of nucleotides –Each nucleic acid molecule has its own order, or “sequence,” of nucleotides –The correct sequence of nucleotides is essential for the nucleic acid’s function D.Nucleic Acids

Overall function. The sequence of nucleotides in a nucleic acid molecule serves as a blueprint to encode the correct sequence of amino acids for a protein. The code for a specific protein is called a “gene.” Deoxyribonucleic acid (DNA): DNA molecules (chromosomes) serve as the “master blueprint” for all of the cell’s proteins. The DNA molecules are transmitted to offspring during reproduction. Ribonucleic acid (RNA): RNA molecules serve as “working copies” of the genes for the proteins that the cell is making at any given time. D.Nucleic Acids

Nucleotide structure –A nucleotide consists of: Nitrogenous base Pentose sugar Phosphate group –Nitrogenous bases: Purines: adenine & guanine Pyrimidines: cytosine, thymine (in DNA), & uracil (in RNA) –Pentose sugars: Ribose (found in RNA) Deoxyribose (found in DNA) D.Nucleic Acids