Human Cell Biology and Physiology

1. Human Cell Biology and Physiology Timothy Billington PhD

2. EVERY SILVER LINING HAS ME

3. 7th formative test • Where does most metabolism occur? • What is the process of metabolic turnover? • Why do we say that metabolism is a dual process? • If the organic ‘building blocks’ of metabolism are at a low energy level, which substances are at a high energy level? • Explain in your own words how we envisage the coupling of anabolic and catabolic processes. • What is your definition of Mitosis? • Chromosomes are a multi-super-coiled combination of ………………and……………. • Imagine you are a medical scientist investigating a possible chromosomal abnormality. You start by obtaining some white cells from a patient’s blood and you set up a demonstration of the pairing of chromosomes. What is this pictorial chromosome representation called?

4. Your research assistant tells you that red cells are much easier to obtain and that it would be more simple to obtain an answer on chromosomes that way. Explain why you reject his idea. • When referring to DNA structure, we say that the ………strands of DNA run in an anti-parallel configuration. Explain why we use the term ‘anti-parallel’. • Cytosine and Guanine can have 3 possible hydrogen bonds between them. Explain in your own words the atomic environment of these 3 bonds. • Adenine and Thymine can have only ………hydrogen bonds between them. From your knowledge of their structures, explain why it is not possible to have ……hydrogen bonds. • DNA polymerase can construct a complementary DNA strand using a single strand of DNA as a template. However, DNA polymerase cannot ‘see’ that template strand unless an enzyme called …………………………… goes into action. • What does this enzyme action involve?

5. DNA: base-pairing via hydrogen bonds Nucleotide bases (C&T) Hydrogen bonding Nucleotide bases (A&G) Base-pairing rules: Aonlypairs with T , Conlypairs with G

6. We say that DNA replication during mitosis is ‘semi-conservative’. What do we mean by that? • In the process of m-RNA formation, known as …………, which enzyme is acting? • If we neglect the two sex-determining chromosomes, how many pairs of chromosomes make up the normal human genome? • In the process of protein synthesis, which type of covalent bond forms between adjacent amino acids? • What name has been given to the transfer of information from m-RNA to amino acid chains. • Consider the DNA sequence ACT GCA GAT TTC CGA GAC TAT. This sequence suffers an UV mutation which knocks out the T of the ACT triplet. Write out the post-mutation DNA sequence. • From that sequence, predict the sequence of the resulting m-RNA strand. • From that m-RNA strand, predict the t-RNA anti-codons which could bind to the m-RNA codons.

8. Week 10 begins here: December 8th, 2016 2 Topics ENERGY GENERATION IN MITOCHONDRIA KREBS CYCLE (= CITRIC ACID CYCLE) BRUSH UP ON BLOOD GROUPS

9. Questions: 1. Where in the cell does Glycolysis take place? 2. What is the starting molecule for glycolysis? 3. Which molecule is the final product of glycolysis ? 4. Where in the cell does that molecule end up?

10. GOINGS-ON INSIDE a MITOCHONDRION 1. Krebs Cycle ( = Citric Acid Cycle = Tri-Carboxylic Acid [TCA ] Cycle) 2. Electron Transport Chain

11. Remember that at the end of Glycolysis, we produce 2 molecules of Pyruvic Acid, for every molecule of Glucose that is catabolised. C-C-C-C-C-CC-C-C + C-C-C Although one molecule of Glucose yields 2 ATP molecules, there is still plenty of energy locked up in the covalent bonds of Pyruvic Acid. Cell’s ability to capture that energy relies on the presence of Oxygen. If there IS adequate oxygen available, then Pyruvate enters the mitochondrion and is broken down in the Citric Acid Cycle

12. CITRIC ACID CYCLE Pyruvate (3-carbon) CO2 Acetyl Coenzyme A (2-carbon) Coenzyme A 4-carbon Citric acid (6-carbon) 2H CO2 2H2H 4-carbon 5-carbon CO2 2H ATP ATP

13. FUNCTION OF THE CITRIC ACID CYCLE • remove hydrogen atoms from organic molecules • transfer the hydrogen atoms to coenzymes, NAD and FADH • What is happening in the Citric Acid Cycle? • 1. The 2-carbon acetyl group, carried by coenzyme A, is transferred to a 4-carbon molecule to make a 6-carbon molecule (citric acid). Coenzyme A is recycled and picks up another acetyl group • 2. The 2 carbon atoms are removed and combined with oxygen to make two CO2 molecules • 3. The Hydrogen atoms are removed by coenzymes NAD and FADH

14. ELECTRON TRANSPORT SYSTEM The citric acid cycle breaks down 2 pyruvate molecules, transferring hydrogen atoms to NAD ( NAD + H NADH) and to FADH (FADH + H FADH2) In exchange for the hydrogens, the two Coenzymes provide electrons to the electron transport chain through the Cytochrome system Each of the molecules of NADH yield 3 ATP and 1 water molecule Each of the FADH2 molecules yields 2 ATP and 1 water molecule

15. NEXT TOPIC: REPEAT OF BLOOD GROUP DISCUSSION

16. BLOOD GROUPS A,B,O and OTHERS Sci & Civ Dr T BILLINGTON U3A 2007

17. Type O: universal distribution • Type A: abundant in W. Europe, Mediterranean, Turkey, Balkans and Japan • Type B: response to bacterial infections of communal living and to dietary changes. Found in Europe, Asia, Mongolia, Korea, China, India and Jewish groups • Type AB: is relatively recent & may have resulted from mixing of populations ABO GROUPS Sci & Civ Dr T BILLINGTON U3A 2007

18. Genes for A, B produce enzymes (= proteins) called transferases. DNA on Chr 9Transferase Enzymes Transferases move carbohydrate molecules (sugars) from carriers in plasma to acceptors on red cell surfaces Sugars on carriers Sugars on red cell surfaces Transferases Sci & Civ Dr T BILLINGTON U3A 2007

19. Aand B are co-dominant Any McCause why you can’t remember that? Sci & Civ Dr T BILLINGTON U3A 2007

20. WHATARE the BLOOD GROUPS? Red blood cells (rbc) have chemical groups on them facing the outside. The groups are called ANTIGENS. They are very large SUGAR molecules with added nitrogen and hydrogen atoms Blood plasma, in which the rbc are suspended, contains the ANTIBODIES directed against the missingANTIGEN Sci & Civ Dr T BILLINGTON U3A 2007

21. Red cell with surface antigens Plasma, the fluid part of blood Antibodies Sci & Civ Dr T BILLINGTON U3A 2007

22. Consider people whose blood is type A They will have the A antigen on their red blood cells In their plasma, they will have antibodies directed against the B antigen BLOOD PLASMA Sci & Civ Dr T BILLINGTON U3A 2007

23. Let’s get an idea of the size of red blood cells Sci & Civ Dr T BILLINGTON U3A 2007

24. Red Blood Cells inside an artery In a cubic millimetre of blood: 4.2 – 5.5 million rbc in females 4.5 – 6.3 million rbc in males mm3 1 Sci & Civ Dr T BILLINGTON U3A 2007

25. Antigen group on rbc membrane surface TYPE A acetyl-galactosamine TYPE Bgalactosamine TYPE ABacetyl-galactosamineand galactosamine TYPE O - - no antigens Sci & Civ Dr T BILLINGTON U3A 2007

26. Here’s the chemistry of those surface antigens Sci & Civ Dr T BILLINGTON U3A 2007

27. This carbohydrate group is on RBC of Type O But is NOT ANTIGENIC Lacks antigenicity B-type transferase A-type transferase Galactose B antigen A antigen N N-acetyl glucosamine Sci & Civ Dr T BILLINGTON U3A 2007

28. ‘If I can understand it, then Youcan’ Sci & Civ Dr T BILLINGTON U3A 2007

29. As we have seen, Antigenic specificity, i.e. whether the cell is A or B or O, is determined by the types of carbohydrate molecules that are on the external surface of the red blood cell Incidentally, Type O means that the red cells have neither A nor B antigens. Sci & Civ Dr T BILLINGTON U3A 2007

30. I don’t know what my blood type is, but I’ve just taken your fruit loop! Maybe I’m type O Sci & Civ Dr T BILLINGTON U3A 2007

31. Suck it and see……. Sci & Civ Dr T BILLINGTON U3A 2007

32. Back to serious stuff Sci & Civ Dr T BILLINGTON U3A 2007

33. Notice how the antigeniccarbohydrate molecule protrudes out of the rbc into the blood plasma PLASMA Membraneof red blood cell CYTOPLASM Sci & Civ Dr T BILLINGTON U3A 2007

34. Let’s look at these in terms of what you ‘see’ on the Red Blood Cell external surface These are called phenotypes, i.e. the physical indirect results of the genes being expressed phenotypes Sci & Civ Dr T BILLINGTON U3A 2007

35. AB Anti-Bantibodies in plasmaAnti- Aantibodies in plasma ABO RBC RBC RBC RBC NO antibodies in plasma BOTH antibodies in plasma Sci & Civ Dr T BILLINGTON U3A 2007

36. Type O has both anti-A& anti-B antibodies in plasma. Transfusion with either A or B blood causes agglutination (= clumping of rbc) Type A has anti-B antibodies in plasma. So transfusion with blood type Bwould cause agglutination Sci & Civ Dr T BILLINGTON U3A 2007

37. Type B has anti-A antibodies in plasma. Transfusion with blood type A would cause agglutination Type AB carries NOanti-A or anti-B antibodies in plasma, therefore neither type A nor B blood could cause agglutination Sci & Civ Dr T BILLINGTON U3A 2007

38. Remember: in a sample of whole blood, the red cells are suspended in plasma Red cell surfaces carry the Antigens Plasma carries the opposingAntibodiesin solution Sci & Civ Dr T BILLINGTON U3A 2007

39. NOT possible to have an Antigen on the RBC in the presence of its own Antibody in the plasma Sci & Civ Dr T BILLINGTON U3A 2007

40. WHAT if an ANTIGENDOES MEET its ANTIBODY…? Ag + AbAgAb complex (agglutination) Needs to be carefully considered b4 a blood transfusion is done. Medical personnel are required to cross-match blood types to make sure there is NOAgAbcomplex formation Agglutination means that a large proportion of the blood system ‘clumps’ and death may ensue. Red blood cells stick irreversibly to one another in a 3-D mesh Sci & Civ Dr T BILLINGTON U3A 2007

41. What happens if you Transfuse with non-cross-matched blood, i.e.with thewrong blood group? Before transfusion After transfusion Red blood cells in suspension in the blood stream Agglutinated red blood cells. They have formed 3-d clumps (= ‘clotted’ ) Sci & Civ Dr T BILLINGTON U3A 2007

42. Appearance on a haematology slide in the lab? Blood of the wrong group has been added to the blood sample in the centre section Sci & Civ Dr T BILLINGTON U3A 2007

43. GOODBYE to A,B,O blood types April 1st, 2007 saw the discovery of 2 enzymes which safely convert blood groups A, B and AB to group O Enzymes are glycosidases and were derived from bacteria. Glycosidases cleave off the carbohydrates that compose the A and B antigens on red blood cells Treat with glycosidases AB O Sci & Civ Dr T BILLINGTON U3A 2007

44. GOODBYE to A,B,O blood types SO….once the safety of the glycosidase treatment is established, all blood could be converted to type O development of universal red blood cells which could improve the blood supply at blood banks and enhance the safety of clinical transfusions. They could be donated to any body, independent of the receiver’s blood type Rh (Rhesus) antigen remains a concern, however…. Sci & Civ Dr T BILLINGTON U3A 2007

45. other blood groups………. All these are determined by proteins expressed on rbc membranes Question: Which type of protruding molecule determines A,B, O blood groups? Sci & Civ Dr T BILLINGTON U3A 2007

46. Yes, proteins this time, notcarbohydrates Direct gene products Sci & Civ Dr T BILLINGTON U3A 2007

47. Colton antigen ( Co ) On membranes of rbc and in the kidney. Co antigen= part of a protein called an aquaporin. Aquaporin is responsible for water balance in the body. Is a channel in the membrane through which water can pass into and out of cells. 98% of people have the Co antigen Sci & Civ Dr T BILLINGTON U3A 2007

48. Duffy antigen (Fy) Result of a DNA mutation on Chr 1, where a G was substituted for an A Fy antigen acts as a receptor for malarial parasites People who do nothave Fytendto be resistant to malarial infection Sci & Civ Dr T BILLINGTON U3A 2007

49. Kell antigen Gene is on Chr. 7 Important in susceptibility to haemolytic anaemia Kidd antigen Gene is on Chr. 18 If you don’t have this antigen, you are unable to concentrate your urine XK antigen Gene is on X Chr Without this antigen you are susceptible to red cells bursting (haemolytic anaemia) Sci & Civ Dr T BILLINGTON U3A 2007

50. Cartwright antigen Result of a mutation in the gene for the enzyme which normally breaks down nerve transmitters after they have produced a nerve impulse In people with this antigen the nerve cannot return to its resting state, so cannot carry another action potential Get continuous excessive muscle contraction. Cartwright antigen is thus extremely toxic because the neurotransmitter stays active END Sci & Civ Dr T BILLINGTON U3A 2007