1. Structure and function of cell components (i)Carbohydrates (ii)Lipids (iii)Proteins (iv)Nucleic Acids (v)Membranes (vi)Cytoskeleton

2. Revision What do we remember about the structure of DNA and RNA from Higher?

3. Nucleotide structures The building block of a nucleic acid is a nucleotide. Nucleotides consist of A pentose sugar A pentose sugar A nitrogenous base A nitrogenous base A phosphate group A phosphate group

4. Pentose Sugars Deoxyribose and ribose differ by the group attachment at the 2’C.

5. Bases There are 5 bases There are 5 bases These can be classified into two types These can be classified into two typesPurines Double ringed Double ringed Adenine and Guanine Adenine and Guanine Adenine Guanine

6. Bases cont… Pyrimidines Single ringed Single ringed Cytosine, Thymine and Uracil Cytosine, Thymine and Uracil ThymineCytosine Uracil

7. Formation of a nucleotide A condensation reaction occurs between the OH group on the 5’ C and phosphate group to form a strong phosphodiester bond. A condensation reaction occurs between the base and the 1’ C to form a strong glycosidic bond

8. Formation of a nucleotide cont..

9. Formation of nucleic acid A phosphodiester bond also forms between the 3’ C and the phosphate group of the next nucleotide to form the sugar phosphate backbone.

10. Base Pairing in DNA A and T join by two weak hydrogen bonds G and C join by three weak hydrogen bonds

11. DNA strands DNA strands are antiparallel

12. Revision What do we remember from Higher about replication and transcription? Both processes are controlled by enzymes. Where do you think they need to be used and why? DNA synthesis always proceeds in the direction 5’ to 3’. What problems does this cause and how would you overcome these if you were designing a cell.

13. Enzymes DNA polymerase Catalyses the linking together of DNA nucleotides during replication Catalyses the linking together of DNA nucleotides during replication DNA polymerase can only add a nucleotide to the 3’ end of the previous nucleotide. DNA polymerase can only add a nucleotide to the 3’ end of the previous nucleotide. RNA polymerase Catalyses the linking of RNA nucleotides during transcription (and in the replication of the lagging strand during DNA replication) Catalyses the linking of RNA nucleotides during transcription (and in the replication of the lagging strand during DNA replication)

14. Enzymes cont… DNA ligase Joins short sections of DNA together Joins short sections of DNA together DNA replication animation: http://207.207.4.198/pub/flash/24/menu.swf

15. Learning Activities Read DART pg 48 – 53 and take notes Scholar 4.5 Nucleic Acids worksheet DNA replication worksheet Advanced Higher questions http://www.maxanim.com/genetics/index.htm Look at Look at Replication fork DNA replication Meselson-Stahl experiment Make notes on DNA and RNA structure Make notes on replication and transcription Think about how you will remember which bases are purines and which are pyrimidines Write a summary of all the different bonds formed between molecules by dehydration reactions.