Tour of the Cell 2

1. Tour of the Cell 2 AP Biology

2. Cells gotta work to live! • What jobs do cells have to do? • Job 1: make proteins • proteins control everycell function • Job 2: make energy • for daily life • for growth • Job 3: make more cells • growth • repair • renewal

3. ATP Focus on Job 2: Making Energy

4. Cells need power! • Making energy – 5 requirements (for aerobic cells) • take in or make food • digest food • take in oxygen (O2) • make ATP • remove waste ATP

5. 1. TAKE IN or MAKE food • Heterotrophs take in food • Animals eat stuff and break it down to get energy out of it • Autotrophs make their own food • Plants make their own food and break it down to get energy out of it Eating stuff is pretty straight forward, however Making your own food requires a special Organelle……

6. Chloroplasts • Chloroplasts are plant organelles • class of plant structures = plastids • amyloplasts • store starch in roots & tubers • chromoplasts • store pigments for fruits & flowers • chloroplasts • contain chlorophyll & function in photosynthesis • Capture the energy of sunlight • GREEN • in leaves, other green structures of plants & in eukaryotic algae

7. Chloroplasts • Structure • 2 membranes • Inner and outer • stroma = internal fluid-filled space • thylakoids = membranous sacs where ATP is made • grana = stacks of thylakoids Why internal sac membranes? increase surface area for membrane-bound enzymes that synthesize ATP

8. Chloroplasts • Function • photosynthesis • synthesize sugars • transform solar energy into chemical energy • Use sunlight to produce sugars from CO2 & H2O • Semi-autonomous • moving, changing shape & dividing • can reproduce by pinching in two Who else divides like that? bacteria!

9. + water + energy  glucose + oxygen carbon dioxide light energy  6CO2 + 6H2O + + 6O2 C6H12O6 Membrane-bound Enzymes do photosynthesis FOOD!!

10. Chloroplasts Why are chloroplasts green? Photosynthetic Pigment: CHLOROPHYLL!! Captures energy of Sunlight!!

11. Where old organellesgo to die! Digesting Food:LYSOSOMES • 2 Functions • little “stomach” of the cell • digests macromolecules • “clean up crew” of the cell • cleans up broken down organelles • Structure • vesicles containing digestive enzymes synthesized by rER, transferred to Golgi only in animal cells

12. 1960 | 1974 Lysosomes as clean up crew: white blood cells attack & destroy invaders = digest them in lysosomes 1974 Nobel prize: Christian de Duve Lysosomes discovery in 1960s

13. Lysosomes as Cellular digesters • Lysosomes fuse with food vacuoles • Cell engulfs food • Packs it in food vacuole • Food vacuole fuses w/ lysosome • Hydrolytic (digestive) enzymes break polymers into monomers • Monomers pass to cytosol to become nutrients of cell • lyso– = breaking things apart • –some = body

14. Lysosomal enzymes • Lysosomal enzymes work best at pH 5 • organelle creates custom pH • how? • proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome • Proton Pumps • why? • enzymes are very sensitive to pH • why? • enzymes are proteins — pH affects structure (denature) • why evolve digestive enzymes which function at pH different from cytosol? • It’s a safeguard! Digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself! Lysosomes also emphasize The importance of COMPARTMENTALIZATION In cells. Keep incompatible processes SEPARATE. Digestion MUST be isolated!

15. When things go bad… • Diseases of lysosomes are often fatal • digestive enzyme not working in lysosome • picks up biomolecules, but can’t digest one • lysosomes fill up with undigested material • grow larger & larger until disrupts cell & organ function • lysosomal storage diseases • more than 40 known diseases • example:Tay-Sachs diseasebuild up undigested fat in brain cells

16. Lysosomal storage diseases • Lipids • Gaucher’s disease • Niemann-Pick disease • Tay Sachs • Glycogen & other poylsaccharides • Farber disease • Krabbe disease • Proteins • Schindler’s disease

17. But sometimes cells NEED to die… • Lysosomes can be used to kill cells when they are supposed to be destroyed • some cells have to die for proper development in an organism • apoptosis • “auto-destruct” process • lysosomes break open & kill cell • ex: tadpole tail gets re-absorbed when it turns into a frog • ex: loss of webbing between your fingers during fetal development

18. syndactyly Fetal development 6 weeks 15 weeks

19. Apoptosis • programmed destruction of cells in multi-cellular organisms • programmed development • control of cell growth • example: if cell grows uncontrollably this self-destruct mechanism is triggered to remove damaged cell • cancer must over-ride this to enable tumor growth

20. Autophagy • Recycling of the cell’s own material by lysosomes • Known as autophagy • Lysosome engulfs another organelle or piece of cytosol • Polymers of the structure are broken down and monomers are returned to the cell for re-use

21. Once large molecules are broken down, they must be used for Making Energy • Cells must convert incoming energy to forms that they can actually use for work • from glucose to ATP • mitochondria: • Organelles that take HUGE glucose and convert it to a more usable form ATP • Like taking a $100 bill and breaking it into $1 bills that are easier to spend ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP

22. Mitochondria • Function • cellular respiration • Catabolic process • Break down • generate ATP • from breakdown of sugars, fats & other fuels • in the presence of oxygen • break down larger molecules into smaller to generate energy = catabolism • generate energy in presence of O2 = aerobic respiration

23. Mitochondria • Structure • 2 membranes • smooth outer membrane • highly folded inner membrane • Cristae • Increases surface area for membrane bound enzymes that make ATP • More enzymes = more ATP • fluid-filled space between 2 membranes • internal fluid-filled space • mitochondrial matrix • DNA, ribosomes & enzymes

24. Mitochondria

25. glucose + oxygen  carbon + water + energy  C6H12O6 + 6O2 6CO2 + 6H2O + ATP dioxide Membrane-bound Enzymes

26. Mitochondria • Almost all eukaryotic cells have mitochondria • there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria • number of mitochondria is correlated with aerobic metabolic activity • more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: • muscle cells • nerve cells

27. Mitochondria are everywhere!! animal cells plant cells

28. Mitochondria & Chloroplasts • Important to see the similarities • Both transform energy from one form to another • Chloroplast: Sunlight energy > chemical energy stored in food • Mitochondrion: Chemical energy stored in food > chemical energy stored in ATP • double membranes = 2 membranes • semi-autonomous organelles • move, change shape, divide • internal ribosomes, DNA & enzymes

29. Mitochondria & chloroplasts are different from other organelles • Mitochondria and Chloroplasts are not part of endomembrane system • Mitochondria and Chloroplasts Grow & reproduce • semi-autonomous organelles • Mitochondria and Chloroplasts possess their own ribosomes • ribosomes like bacterial ribosomes • Mitochondria and Chloroplasts possess their Own circular chromosome Who else has a circular chromosome not bound within a nucleus? bacteria

30. Dividing Mitochondria Who else divides like that? What does this tell us about the evolution of eukaryotes?

31. 1981 | ?? Endosymbiotic theory • Mitochondria & chloroplasts were once free living bacteria • engulfed by ancestral eukaryote • Endosymbiont • cell that lives within another cell (host) • as a partnership • evolutionary advantage for both • one supplies food OR energy • the other supplies raw materials & protection Lynn Margulis U of M, Amherst

32. Endosymbiosis theory Evolution of eukaryotes

33. + water + energy  glucose + oxygen carbon dioxide glucose + oxygen  carbon + water + energy  C6H12O6 + 6O2 6CO2 + 6H2O + ATP dioxide light energy  6CO2 + 6H2O + + 6O2 C6H12O6 Relationship b/t mitochondria and chloroplasts Photosynthesis Respiration

34. The Great ENERGY Circle of Life sun Photosynthesis ATP plants glucosesugar O2 + CO2 + H2O Respiration animals & plants ATP

35. food vacuoles Food & water storage plant cells central vacuole animal cells contractilevacuole

36. Vacuoles • Function • Food “transfer ships” • Food vacuoles • phagocytosis, fuse with lysosomes • little “pumps” • Contractile vacuoles • in freshwater protists, pump excess H2O out of cell • Storage containers • Central vacuoles • in many mature plant cells

37. Vacuoles in plants • Functions • storage • Storing water • stockpiling proteins or inorganic ions • depositing metabolic byproducts • storing pigments • Other than chlorophyll • storing defensive compounds against herbivores • selective membrane • control what comes in or goes out

38. Peroxisomes • Other digestive enzyme sacs • in both animals & plants • breakdown fatty acids to sugars • easier to transport & use as energy source • detoxify cell • detoxifies alcohol & other poisons • produce peroxide (H2O2) • must breakdown H2O2 H2O • Contain an enzyme that does this • CATALASE

39. Putting it all together animal cells plant cells

40. Any Questions??