CELL CHEMISTRY IV Proteins & Nucleic Acids

1. CELL CHEMISTRY IVProteins & Nucleic Acids Plasma proteins that you must know Deoxyribonucleic acid (DNA) Ribonucleic acids (RNAs)

2. Significance of Proteins in Physiology • They are responsible for the unique structure and specific functions of cells • They function as • Enzymes • Chemical messengers (hormones & neurotransmitters) • Carriers/Transporters (in blood and in cells) • Channels (in cell membranes) • Receptors for hormones & neurotransmitters • Immunity (vaccination)

3. Know These Proteins and Their Respective Function! • Hemoglobin: • Transports O2; Inside red blood cells; binds O2 reversibly • Lactase: • Catalyzes hydrolysis of lactose into --- (what products?) • Carbonic anhydrase: • Catalyzes synthesis of H2CO3 from CO2 and H2O • Actin and Myosin: • For muscle contraction and relaxation; Interaction between these two generates forces that cause movement • Albumin: • Most abundant protein in plasma; Major role in plasma oncotic (or osmotic pressure) • Immunoglobulins (Ig) G, E • Also called antibodies; Immunity (as in vaccination) and allergic reaction (IgE) • Keratin: • Structural protein in cells, nails, hair • Ferritin: • Intracellular storage of iron

4. Some Facts on Proteins • They are polymers of amino acids that are joined by peptide bonds. • Each protein has a specific or unique amino acid sequence (AAS) • The AAS determines the 3D structure and the function/s of a protein • Questions • Peptide bonds are formed by what type of chemical reaction ---? • What enzyme catalyzes the synthesis of peptide bonds? • What organelle has this enzyme?

5. More Facts About Proteins • 3D structure that is maintained by hydrogen bonds and ionic bonds • Function/s depend on 3D structure • Can be denatured (Denaturation) by • A) extremes of pH • B) heat • Questions: • Would denaturation affect the properties, structure and function of a protein? • An example of denaturation in your kitchen?

6. Hemoglobin: 3D Structure • Notice 4 proteins interact to form a single structure (a quarternary structure). • Hemoglobin is a multimericprotein • What type of bonds stabilize the “globular” shape of hemoglobin?

7. Some More Facts About Proteins • There are thousands of proteins inside a cell • To synthesize proteins, cells need information from a gene (genetic information) • A Gene is a sequence of nucleotides that has information for the synthesis of a functional RNA or for a protein. in DNAmolecule. • The nucleotide sequence in a genedictates the amino acid sequence of the protein or nucleotide sequence of functional RNA encoded in the gene

8. Protein SynthesisStudy/Review Guyton Ch. 3 • To synthesize proteins, cells need: • Genetic information (Gene) • mRNA, tRNA • Ribosomes • Amino acids (20 different) • Energy • The key events that you MUST review in any textbook of biology or college Anat & Physiol or in Guyton: • Transcription (RNA synthesis) • Translation (protein synthesis) • Replication (DNA synthesis)

9. Flow of Genetic information(Guyton Ch. 3) • In all cells, the flow of genetic information is from: • Gene --> mRNA --> Protein • Transcription • The enzyme RNA polymeraze catalyzes the synthesis of phosphodiester bond between ribonucleotides. • The enzyme uses one of the two DNA strands as a template • Notice that DNA IS NOT CONVERTED TO RNA • Questions • Given the nucleotide sequence: …-T A C G A A C C G A T-… • Write the sequence of the complementary strand? • These two strands would be held together by what bonds? • Assuming that the bottom strand (answer to #1 is the gene), write the sequence of the transcribed mRNA?

10. Nucleic Acids Some Facts plus Some Illustrations

11. Nucleic Acids • The nucleic acids are DNA and RNA • DNA is found in the nucleus and mitochondria • RNA is found in the cytoplasm • There are several types of RNA • mRNA (m = messenger) • rRNA (r = ribosomal) • tRNA (t = transfer) • They are all Polymers of nucleotides joined by ---? formed by what type of reaction?

12. Composition of Nucleotide

13. RNAs: Function of Each • mRNA is a copy of the information in the gene. • tRNAs, in collaboration with ribosomes, translate the message in the mRNA. Notice that during protein synthesis, a sequence of ribonucleotidesis translated into a sequence of amino acids. • Each codon(a set of 3 consecutive ribonucleotides) of the mRNA is a code for one amino acid in the protein. • rRNAs are structural component of ribosomes. They function as enzymes (ribozymes) that catalyze the formation of peptide bonds.

14. Be Able to Distinguish Amino AcidfromNucleotide

15. DNA: Composition & Structure (1)

16. DNA vsRNA (1) • DNA • Found in the nucleus and mitochondria • Double stranded and shaped as twisted ladder • Contains the pentosedeoxyribose • Contains the nucleotides A, T, G, C • In the double strand, A is structurally complementary to T and G is complementary to C (A:::T, G:::C) • RNA

17. DNA: Composition & Structure (2)

18. RNA vsDNA (2) • RNA • Found in cytoplasm (cytosol, ribosomes) • Is single stranded • Contains the pentose ribose • Contains the nucleotides A, U, G, C • During transcription, DNA strand serves as template for RNA synthesis and A is complementary to U, G is complementary to C. (A:::U, G:::C)

19. Some Questions ?? • Given the ….-5’-ACGTCACTCAGTGGATCA-…. • Write the sequence of the complementary strand • Assume that the 3’- strand (answer to 1 above) is the gene. • What is the sequence of the mRNA from that gene? • How many codons are there in that (#2) mRNA? • Write each codon on a separate line in your notes and for each codon, write the sequence of the corresponding anticodon • Which RNA has anticodons? • What is the function of these RNAs(answer to #5) RNAs • According to the genetic code (consult Guyton Table 3.1), what is the amino acid sequence of the peptide from that gene?