The Chemical Building Blocks of Life

1. The Chemical Building Blocks of Life Chapter 3

2. Outline • Biological Molecules • Macromolecules • Proteins • Structure and Denaturation • Nucleic Acids • DNA and RNA • Lipids • Fats and Phospholipids • Carbohydrates • Transport and Storage

3. Biological Molecules • The framework of biological molecules consists of carbon bonded to other carbon molecules, or other types of atoms. • Hydrocarbons consist of carbon and hydrogen. • Covalent bonds store considerable energy.

4. Biological Molecules • Functional groups • specific groups of atoms attached to carbon backbones • retain definite chemical properties • Macromolecules. • proteins • nucleic acids • lipids • carbohydrates

5. Macromolecules • Macromolecules are often polymers. • long molecule built by linking together small, similar subunits • Dehydration synthesis removes OH and H during synthesis of a new molecule. • Hydrolysis breaks a covalent bond by adding OH and H.

6. Proteins • Protein functions: • enzyme catalysis • defense • transport • support • motion • regulation • storage

7. Amino Acids • contain an amino group (-NH2), a carboxyl group (-COOH) and a hydrogen atom, all bonded to a central carbon atom • twenty common amino acids grouped into five classes based on side groups • nonpolar amino acids • polar uncharged amino acids • charged amino acids • aromatic amino acids • special-function amino acids

8. Amino Acids • Peptide bond links two amino acids. • A protein is composed of one or more long chains of amino acids linked by peptide bonds (polypeptides).

9. Protein Structure • Protein function is determined by its shape. • Protein structure • primary - specific amino acid sequence • secondary - folding of amino acid chains • motifs - folds or creases • supersecondary structure

10. Protein Structure • tertiary - final folded shape of globular protein • domains - functional units • quaternary - forms when two or more polypeptide chains associate to form a functional protein

11. Chaperone Proteins • Chaperone proteins are special proteins which help new proteins fold correctly. • Chaperone deficiencies may play a role in facilitating certain diseases.

12. Unfolding Proteins • Denaturation refers to the process of changing a protein’s shape. • usually rendered biologically inactive • salt-curing and pickling used to preserve food

13. Nucleic Acids • Deoxyribonucleic Acid (DNA) • Encodes information used to assemble proteins. • Ribonucleic Acid (RNA) • Reads DNA-encoded information to direct protein synthesis.

14. Nucleic Acid Structure • Nucleic acids are composed of long polymers of repeating subunits, nucleotides. • five-carbon sugar • phosphate • nitrogenous base • purines • adenine and guanine • pyrimidines • cytosine, thymine, and uracil

15. Nucleic Acid Structure • DNA exists as double-stranded molecules. • double helix • complementary base pairing • hydrogen bonding • RNA exists as a single stand. • contains ribose instead of deoxyribose • contains uracil in place of thymine

16. Structure of DNA

17. Lipids • Lipids are loosely defined as groups of molecules that are insoluble in water. • fats and oils • Phospholipids form the core of all biological membranes. • composed of three subunits • glycerol • fatty acid • phosphate group

18. Fats and Other Lipids • Fats consist a of glycerol molecule with three attached fatty acids (triglyceride / triglycerol). • Saturated fats - all internal carbon atoms are bonded to at least two hydrogen atoms • Unsaturated fats - at least one double bond between successive carbon atoms • Polyunsaturated - contains more than one double bond • usually liquid at room temperature

19. Fats as Energy Storage Molecules • Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates. • Animal fats are saturated while most plant fats are unsaturated. • Consumption of excess carbohydrates leads to conversion into starch, glycogen, or fats for future use.

20. Carbohydrates • Carbohydrates are loosely defined as molecules that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio. • monosaccharides - simple sugars • disaccharides - two monosaccharides joined by a covalent bond • polysaccharides - macromolecules made of monosaccharide subunits • isomers - alternative forms of the same substance

21. Carbohydrate Transport and Storage • Transport disaccharides • Humans transport glucose as a simple monosaccharide. • Plants transform glucose into a disaccharide transport form. • Storage polysaccharides • plant polysaccharides formed from glucose - starches • most is amylopectin

22. Structural Carbohydrates • Cellulose - plants • alpha form or beta form of ring • Chitin - arthropods and fungi • modified form of cellulose

23. Summary • Biological Molecules • Macromolecules • Proteins • Structure and Denaturation • Nucleic Acids • DNA and RNA • Lipids • Fats and Phospholipids • Carbohydrates • Transport and Storage