Understanding DNA, RNA, and Protein Synthesis Processes

1. Learning Outcomes: • Describe how DNA and RNA encode for the amino acid sequence in a polypeptide chain. • Describe the structure of DNA and RNA in terms of a sugar–phosphate backbone and attached bases. • Storyline EP2(p 144 to 149) Activities EP2.7 and EP2.8. • Explain the role of hydrogen bonding in the pairing of bases in DNA, and the replication of genetic information by RNA. • Illustrate and explain the role of hydrogen bonds as intermolecular forces, which help determine the sequence of amino acids in a polypeptide chain. Chemical Ideas: Chapter 5.4 (p 102 to 108)

2. Cell structure cytoplasm ~ gel of molecules Rough endoplasmic reticulum ~ protein synthesis Nucleus DNA ~ genetic material Ribosomes ~ protein synthesis

3. DNA ~ genetic information and the blue print for protein synthesis • Bases in DNA: • Thymine T • Cytosine C • Adenine A • Guanine G Hydrogen bonds between base pairs

4. Part of a DNA strand- a gene – unzips and transcription of the base pairs produces a strand of mRNA.

5. RNA ~ Ribonucleric acid in a cell 1 gene 1 polypeptide chain Transcription DNA used as a blue print to make mRNA Nucleus (DNA) mRNA carries the code for protein synthesis andgoes toribosomes. tRNA collect amino acids in the cell’s cytoplasm and carry them to the ribosomes where they will be built into a polypeptide chain~ translation

6. Bases carried on the DNA strands code for an amino acid sequence that will form a protein. • Bases in RNA: • Uracil U • Cytosine C • Adenine A • Guanine G • Bases in DNA: • Thymine T • Cytosine C • Adenine A • Guanine G How bases pair to form mRNA: Adenine A Uracil U Cytosine C Guanine G Thymine T Adenine A Guanine G Cytosine C

7. Three bases ~ tripet base codes, or codons, are used for each amino acid. in this example it would bind to GCC, the codon for alanine Anti-codon for binding to a codon on mRNA: mRNA from the nucleus

8. sugar phosphate molecule base Bases that make up the triplet base codons are attached to sugar phosphate molecules, which together are called RNA

9. Chemical composition of Ribonucleric Acid Ribose sugar molecules ~ C5H10O5 Phosphate groups H2PO4 One of 4 bases: A,U,G or C

10. OH H O H2O BASE O H2O O phosphate A unit of RNA

11. Representations of the structure of RNA

12. CH3 CH3 H2N H2N - C - - C - COOH C = O H H How an ester bond is formed between the tRNA and an alanine molecule: an ester link alanine molecule + H2O onetRNA

13. When a tRNA collects an amino acid it takes it to the mRNA strand that has become attached to a ribosome.

14. Ribosome moles along the mRNA chain Protein synthesis: ribosome read codons on mRNA.

15. H2N Amino acids bond into the polypeptide chain tRNA molecules bring amino acids to the mRNA in the ribosome COOH tRNA leave the ribosome when it has delivered its amino acid

16. The bases in RNA are planar and the bases fit together so that groups are in just the right positions for hydrogen bonds to form ~ molecular recognition. 2 hydrogen bonds between uracil and adenine

17. 3 hydrogen bonds between cytocine and guanine

18. Read in Chemical Storylines: EP2 Protein building pages 140 to 149 Make your own summary notes/annotated diagrams about how amino acids are converted into polypeptide chains inside cells