Mastering Biological Macromolecules: Carbohydrates, Lipids, Proteins, and Nucleic Acids

1. Biological Macromolecules • Carbohydrates • Lipids • Proteins • Nucleic acids

2. 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

3. A. Carbohydrates • 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

4. B. Lipids • 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

5. B. Lipids • Generalized structure of a triglyceride:

6. 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

7. 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

8. C. Proteins • 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. D. Nucleic Acids • 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

15. 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.

16. 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)