1. Biology 12 – the nucleus

2. Cell structures Is this eukaryotic? yes Why? nucleus Is this a plant or animal cell? animal Why? No cell wall or chloroplasts Label the structures Smooth endoplasmic reticulum

3. The nucleus From http://www.bio.jhu.edu/~corces/Research2.html Nucleus contains DNA DNA consists of a double helix tightly coiled DNA is arranged in chunks called chromosomes Different species have different numbers of chromosomes Chromosomes are only visible during cell division

4. Experiments with the nucleus 1 This shows nucleus is responsible for cell survival and division

5. Experiments with the nucleus 2 This shows nucleus is necessary for normal cell development

6. Experiments with the nucleus 3 This shows nucleus controls development of special cell structures eg fruiting bodies

7. Structure of DNA DNA is a coiled double helix made up of nucleotides on a sugar phosphate backbone

8. DNA is made of nucleotides

9. Base pairing Adenine always pairs with Thymine Thymine always pairs with Adenine Cytosine always pairs with Guanine Guanine always pairs with Cytosine

10. Why is DNA important It can be inherited (passed on in cell divisions) It can easily be copied with a high degree of accuracy It controls which proteins are made

11. DNA controls protein synthesis

12. Definitions Transcription Translation Codon Anticodon t-RNA m-RNA r-RNA Protein Amino acid Copying of DNA to make RNA Reading of mRNA to make proteins 3 unit segment of mRNA – codes for particular amino acid 3 unit segment of tRNA (carrying a particular amino acid) that is the reverse of the codon on mRNA Carries amino acids to the ribosome Has the set of instructions for the order in which amino acids are to be assembled into proteins Makes up the ribosomes, where amino acids are assembled into proteins Long chains of amino acids, usually folded Building blocks of proteins

13. Why are proteins important? Roles of proteins in the body include Structural proteins eg collagen, keratin Enzymes (organic catalysts) eg digestive enzymes Transport proteins eg haemoglobin Regulatory proteins eg hormones Protective proteins eg antibodies, clotting factors

14. RNA is made of nucleotides Very similar to DNA except: Thymine is replaced by Uracil The sugar in the sugar-phosphate backbone is different (ribose) Strands are single not double There are 3 types – mRNA, tRNA and rRNA

15. RNA structure Messenger RNA Transfer RNA Ribosomal RNA