PROTEINS

1. PROTEINS • The most complex and multifunctional class of organic molecules • Most genes are instructions for making protein molecules • Large molecules with complex 3-dimensional shapes • Polymers of amino acids

2. Protein functions • Catalytic – enzymes control reactions • Structural – e.g. collagen, keratin, silk • Storage – of amino acids for growth • Transport – e.g. O2 and hemoglobin • Hormones – communication among cells • Receptors – receiving chemical signals • Contractile – e.g. actin and myosin • Defensive – e.g. antibodies

3. O Carboxyl Amino C C O-H H2N “R” O H H O- C C +H3N Functional group varies- >20 kinds “R” Amino acid structure Ionized form

4. O H O- C C +H3N “R” asymmetric α-carbon enantiomers Only L-forms are made and used by organisms

5. The 20 amino acids of proteins: nonpolar, hydrophobic side chains

6. The 20 amino acids of proteins: polar and electrically charged side chains

8. Proteins have complex, 3-D shapes Alternative diagrams of the protein lysozyme

9. Primary structure • the amino acid sequence of a protein • Determined by the genetic information that directs protein synthesis

10. A single amino acid substitution in a protein causes sickle-cell disease

11. Secondary structure • repetitive folding due to H-bonds between amino and carbonyl • α-helix and β-sheet

12. Tertiary Structure -non-repeating folding

13. Quaternary structure- multimeric proteins

14. Review: the four levels of protein structure

15. Denaturation Disruption of 2°, 3°, or 4° structure by heat, pH, or ions = “cooking”

16. NUCLEIC ACIDS (DNA, RNA)=polynucleotides • polymers of nucleotides • Nucleotide structure: N Nitrogenous base N pentose phosphate

18. Nucleotide function • nucleoside triphosphates- (ATP, GTP) are energy carriers • Monomers for building polynucleotides Polynucleotide function • DNA, RNA are information carriers • Some RNA’s are catalysts More about nucleic acids later, when we consider molecular genetics