Cellular Metabolism & Reproduction: Mitosis & Meiosis

2. Chapter 4 Cellular Metabolism and Reproduction: Mitosis and Meiosis

3. Introduction to Cellular Metabolism • Metabolism: total cellular chemical changes • Anabolism: process of building up • Catabolism: process of breaking down • Calorie: measure of energy contained in food • ATP: energy source available to the cell

4. Cellular Metabolism or Biochemical Respiration

5. Glycolysis • Breakdown of glucose • Anaerobic or aerobic process • Final outcome • 2 pyruvic acid molecules, 2 ATP molecules (anaerobic), 8 ATP molecules (aerobic)

6. The Krebs Citric Acid Cycle • Pyruvic Acid > Acetic Acid > Acetyl-CoA • Acetyl-CoA enters Krebs cycle in mitochondria • Final outcome • 6 CO2, 8 NADH2, 2 FADH2, 2 ATP (GTP)

7. The Electron Transport (Transfer) System • Series of reduction/oxidation reactions • Requires O2 • Electron carriers • Number of ATP molecules dependent on electron carrier • Water is a waste product

8. Summary of ATP Production • During glycolysis, the citric acid cycle, and electron transport • Glycolysis: 8 ATP (aerobic) • Krebs cycle and electron transport • 28 ATP + 2 GTP or • 30 ATP • 1 glucose molecule yields 38 ATP

9. Anaerobic Respiration

10. Fermentation • Yeast breaks down glucose anaerobically • Pyruvic acid is broken down by decarboxylase • Forms carbon dioxide and acetaldehyde • Final products: 2 ATP, CO2,ethyl alcohol

11. Anaerobic Production of ATP by Muscles • Pyruvic acid converted to lactic acid • Accumulation of lactic acid causes fatigue in muscles • When oxygen is supplied, lactic acid turns back into pyruvic acid • 2 ATP produced per glucose molecule

12. Production of ATP from General Food Compounds

13. Production of ATP from General Food Compounds (cont’d.) • Carbohydrates fit into cellular furnace at same level as glucose • Can be stored in liver or as fat • Fats digested into fatty acids and glycerol • Glycerol enters at PGA stage of glycolysis • Fatty acids enter Krebs citric acid cycle

14. Production of ATP from General Food Compounds (cont’d.) • Proteins digested into amino acids • Enter into Krebs cycle at different stages • Dependent on chemical structure

15. Introduction to Cellular Reproduction

16. Introduction to Cellular Reproduction (cont’d.) • Process of cell duplication • Mitosis: duplication of genetic material • Cytokinesis: duplication of organelles • Meiosis: reduction division only in gonads

17. The Structure of the DNA Molecule

18. The History of the Discovery of DNA • Friedrich Miescher, 1869: first discovery • P.A. Levene, 1920s: composition • Rosalind Franklin: helical structure • Watson and Crick: three-dimensional structure

19. The Anatomy of the DNA Molecule • Double helical chain of nucleotides • Phosphate group • Five-carbon sugars (deoxyribose) • Nitrogen-containing base • Pyrimidines (thymine and cytosine) • Purines (adenine and guanine) • Pyrimidines pair with purines • Chains held together by hydrogen bonds

20. The Anatomy of the DNA Molecule (cont’d.) • Gene: sequence of base pairs that codes for polypeptide or protein • Human Genome Project • 3 billion base pairs that code for 30,000 genes • Duplication of DNA molecule • Helicase separates at hydrogen bonds • DNA polymerase adds new nucleotides

21. The Cell Cycle

22. Introduction • All reproduction begins at cellular level • Interphase • Previously called resting stage • Mitosis • Cytokinesis

23. Interphase • Time between divisions • G1: Primary growth phase • S: DNA duplication • G2: Centrioles complete duplication, mitochondria replicate, chromosomes condense and coil

24. Mitosis • Prophase • Chromosomes become visible as chromatids are joined by centromere • Two kinetochores at the centromere • Centrioles move to opposite poles • Nuclear membrane breaks down • Microtubules attach kinetochores to spindle

25. Mitosis (cont’d.) • Metaphase • Chromatids align at equator of cell • Centromere divides

26. Mitosis (cont’d.) • Anaphase • Divided centromere pulls chromatids to opposite pole • Cytokinesis begins

27. Mitosis (cont’d.) • Telophase • Chromosomes uncoil and decondense • Spindle apparatus breaks down • New nuclear membrane forms • Cytokinesis nearly complete

28. Cytokinesis • Animal cells • Cleavage furrow forms • Cell is pinched into daughter cells • Plant cells • Cell plate forms at equator • Cell plate becomes new cell wall

29. Meiosis: A Reduction Division

30. Introduction • Occurs only in the gonads • Reduces genetic material from diploid to haploid • Two divisions resulting in four cells

31. Stages of Meiosis • Prophase I: homologous chromosomes pair and cross over • Metaphase I: chromosomes align along equator • Anaphase I: centromeres pulled to poles • One member to each pole • Telophase I: one of each pair is at each pole

32. Stages of Meiosis (cont’d.) • Prophase II: spindle forms; centrioles move to poles • Metaphase II: chromosomes line up at equator • Anaphase II: centromeres divide • Telophase II: chromatids at each pole; new nuclear membrane forms

33. Gametogenesis: The Formation of the Sex Cells

34. Gametogenesis: The Formation of the Sex Cells (cont’d.) • Spermatogenesis • Four cells produced • Develop into sperm • Oogenesis • Four cells produced • Only one becomes functional egg

35. Summary • Discussed how glucose is converted into ATP in the presence of oxygen • Discussed how glucose is converted into ATP in the absence of oxygen • Described how fats and proteins are converted into ATP • Discussed the cell cycle