Introduction to Biology

1. Introduction to Biology September 17th 2004 Nancy Van Driessche (email: nv993804@bcm.tmc.edu) Overview of “What is a cell?”: http://www.ncbi.nlm.nih.gov/About/primer/genetics_cell.html

2. What is a cell? • structural and functional units of all living organisms • unicellular and multicellular organisms • bacteria vs. human specialized functions nutrients energy source reproduce

3. Eukaryote vs. Prokaryote eg. fungi animals plants unicellular organisms: yeast, Dictyostelium etc. eg. bacteria Biggest differences: Prokaryotes lack a nuclear membrane! Prokaryotes don't have intracellular organelles! Prokaryotes about 10X size of Eukaryotes.

4. Plasma membrane: a cell's protective coat outside the cell double layer of lipids proteins inside the cell Several functions of membrane proteins: outside the cell inside the cell inport and export of molecules cross-linking of membrane proteins amplification of extracellular signal convertion of product X into product Y

5. The cytoskeleton: a cell's scaffold • very complex and dynamic cell component! • organizes and maintains the cell's shape (e.g. epithelial cells of the gut) • anchors the organells in place • helps during the uptake of external material (endocytosis) • involvement in cell movement • growth

6. The cytoskeleton: a cell's scaffold

7. The cytoplasm (cytosol): a cell's inner space Plasma membrane Cytoskeleton cytosol large fluid-filled space (mostly water + proteins that control most of the cell metabolisms): glycolysis, transcription factors, intracellular receptors etc.

8. Organelles • Nucleus • Protein production machine: the ribosomes • Mitochondria and Chloroplasts • Endoplasmic Reticulum and the Golgi apparatus • Lysosomes and Peroxisomes Adapted and/or specialized for carrying out one or more vital functions. Reminder! Are only found in eukaryotes.

9. Nucleus: a cell's center Function of the nucleus: Structure of the nucleus: - Stores the chromosomes (genetic material) - production of ribosomes in nucleolus - protection of DNA from damaging molecules of molecules that interfere with its processing - DNA replication and synthesis of messenger RNA (mRNA) Note: 2 kinds of genetic material: deoxyribonucleic acid (DNA) ribonucleic acid (RNA) source: http://cellbio.utmb.edu/cellbio/nucleus.html

10. Endoplasmic Reticulum and the Ribosomes: protein production machine Endoplasmic Reticulum (ER) source: http://cellbio.utmb.edu/cellbio/ribosome.htm

11. Endoplasmic Reticulum ER is a continuation of the outer nuclear membrane. ER has smooth regions (responsible for lipid and membrane protein modifications) and rough regions (associated with ribosomes responsible for the synthesis of other proteins) source: http://www.cellsalive.com/cells/er.htm

12. Golgi apparatus • Function: • - modification of lipids and proteins • storage and packaging of materials that will be exported from the cell. source: http://cellbio.utmb.edu/cellbio/golgi.htm

13. Mitochondria • Contain their own genome (distinct from nuclear genome) • Self-replicating • Critical role in generation of energy (called ATP): • Glycolysis (without oxygen use) • Kreb’s cycle (in presence of oxygen)

14. Lysosomes • Rich in digestive enzymes (that work at low pH) • Digest fforeing bacteria that invade a cell • Recycling of membrane components • Repair damage to plasma membrane Peroxisomes • Get rid of toxic substances • Many in the liver lysosome

15. Making new Cells and Cell types (1) Making New Cells Unicellular organisms: Asexual reproduction: replication of genetic material and splitting 1 cell Into 2 identical cells Multicellular organisms: Mitosis to produce for example new skin cells and liver cells. Meiosis or sexual reproduction to create a whole new organism (gametes) Human chromosomes

16. Overview of the major events in mitosis Interphase prophase metaphase anaphase telophase In case of DNA damage or failure of critical processes P53 stimulates induction of inhibitory proteins that halt DNA replication Defects in p53 are associated with a variety of cancers DNA damage repair or initiation of programmed cell death (apoptosis)

17. Overview of the major events in meiosis Production of gametes 2 cell divisions in sequence Big difference between mitosis and meiosis

18. The Working Cell DNA, RNA and Protein Synthesis

19. DNA structure – base pairs adenosine thymine cytosine guanine Source: http://www.blc.arizona.edu/Molecular_Graphics/DNA_Structure/DNA_Tutorial.HTML

20. DNA – The code of life Side view: 3’ end 5’ end Double stranded AT – GC basepairs Right handed spiral View down helix axis: 3’ end 5’ Source: http://www.blc.arizona.edu/Molecular_Graphics/DNA_Structure/DNA_Tutorial.HTML

21. DNA replication Occurs during cell division. Requires: - Helicases (unwind DNA) - DNA polymerases (can bind single Stranded DNA and can move only In 3’ to 5’ direction. - DNA ligase stitches Okazaki fragments Source: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/DNAReplication.html Animation: http://www.phschool.com/science/biology_place/biocoach/dnarep/repstrands.html?blah=&step=6

22. Transcription: RNA synthesis Basic structure of a protein encoding gene: DNA

23. Transcription: RNA synthesis (1) Initiation - Involves transcription factors (TFs) and RNA polymerase - Recognition of TATA box (located ~ 20 to 30 bp of transcription initiation site)

24. Transcription (elongation) (2) /antisense strand

25. Transcription (termination) (3) RNA polymerase falls off terminator Animation: http://www.phschool.com/science/biology_place/biocoach/images/transcription/tcani.gif

26. DNA vs. RNA

27. Post-transcriptional modifications

28. Protein synthesis: Translation initiation

29. Protein synthesis:elongation (2)

30. Protein translation:termination (3)

31. Protein translation: summary Elongation Initiation Termination http://www.phschool.com/science/biology_place/biocoach/translation/init.html

32. Summary