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The Cell

The Cell. Why are cells so small? Why can ’ t they be as huge as an hippo?. What limits cell size?. Surface to volume ratio as cell gets bigger its volume increases faster than its surface area PROBLEMS!!!. What cell organelle governs this?.

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The Cell

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  1. The Cell

  2. Why are cells so small?Why can’t they be as huge as an hippo?

  3. What limits cell size? • Surface to volume ratio • as cell gets bigger its volume increases faster than its surface area • PROBLEMS!!! What cell organelle governs this? Why is a huge single-celledcreature not possible? 6:1 ~1:1 6:1 s:v

  4. Limits to cell size • Metabolic requirements set upper limit • As cells get larger, moving material in & out of cell fast enough to support life is difficult aa aa What process is this? CH NH3 aa CHO O2 CH CHO CO2 CHO CO2 CO2 aa NH3 O2 NH3 O2 NH3 CHO aa CO2 CH aa CH O2 aa O2 What’s the solution?

  5. How to get bigger? DIVIDE! • Become multi-cellular But what challenges do you have to solve now? CO2 CO2 O2 NH3 aa NH3 aa CO2 NH3 O2 CO2 CO2 CH CHO CO2 NH3 aa O2 NH3 NH3 CO2 CO2 CO2 CHO aa NH3 NH3 NH3 CH CHO CO2 CO2 O2 aa aa CH

  6. Cell characteristics • All cells have: • plasma membrane • have cytosol(watery part) • cytoplasm = cytosol + organelles • chromosomes in the form of DNA • Ribosomes • WHAT TYPES OF CELLS ARE THERE? • What about viruses?

  7. Prokaryotebacteria cells Types of cells - no organelles - organelles Eukaryoteanimal cells Eukaryoteplant cells

  8. Prokaryotic cell DNA in nucleoidregion no nucleus Cell wall present in all (type differs) Ribosomes Eukaryotic cell Nucleus present with DNA, Cell walls present in fungi and plants only Membrane bound organelles present MORE COMPLEX! Types of cells • Prokaryotic vs. eukaryotic cells

  9. The prokaryotic cell is much simpler in structure, lacking a nucleus and the other membrane-enclosed organelles of the eukaryotic cell.

  10. Golgi mitochondria chloroplast ER Why have organelles? • Specialized structures • specialized functions • Ex: cilia or flagella for locomotion • Containers • partition cell into compartments • create different local environments • separate pH, or concentration of materials • distinct & incompatible functions • lysosome & its digestive enzymes • Membranes as sites for chemical reactions • unique combinations of lipids & proteins • embedded enzymes & reaction centers • chloroplasts & mitochondria

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

  12. The Protein Assembly Line Golgiapparatus ribosome ER Building Proteins • Organelles involved • nucleus • ribosomes • endoplasmic reticulum (ER) • Golgi apparatus • vesicles nucleus vesicles

  13. large subunit small subunit ribosome Nucleolus • Function • ribosome production • build ribosome subunits from rRNA & proteins rRNA & proteins nucleolus

  14. Ribosomes – make proteins • Freeribosomes • in cytosol • Proteins for INSIDE cell • Bound ribosomes • attached to endoplasmic reticulum • Proteins for OUTSIDE cell membrane proteins

  15. Rough ER function • Finalize protein formation (protein folding = 2nd, 3rd etc.) • protein secreting cells will have lots of RER • packaged into transport vesicles to golgi Which cellshave lot of rough ER?

  16. secretory vesicles transport vesicles Golgi Apparatus • Function • finishes, sorts, tags & ships cell products • like “UPS shipping department” • ships products in vesicles • membrane sacs • “UPS trucks” Which cellshave lots of Golgi?

  17. nucleus cell membrane nuclear pore protein secreted rough ER vesicle ribosome proteins smooth ER transport vesicle Golgi apparatus cytoplasm Putting it together… Making proteins

  18. Smooth ER function • Membrane production • Many metabolic processes • synthesis • synthesize lipids • oils, phospholipids, steroids & sex hormones • hydrolysis • hydrolyze glycogen into glucose • in liver • detoxify drugs & poisons • in liver • ex. alcohol & barbiturates

  19. Where old organellesgo to die! Lysosomes • Function • little “stomach” of the cell • digests macromolecules • “clean up crew” of the cell • cleans up broken down organelles • Structure • vesicles of digestive enzymes synthesized by rER, transferred to Golgi only in animal cells

  20. When cells need to die… • Lysosomes can be used to kill cells when they are supposed to be destroyed • 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

  21. syndactyly Fetal development 6 weeks 15 weeks

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

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

  24. + Making Energy • Cells must convert incoming energy to forms that they can use for work • mitochondria: from glucose to ATP • Cellular Respiration • chloroplasts: from sunlight to ATP & carbohydrates • Photosynthesis ATP ATP

  25. Mitochondria & Chloroplasts • How are they similar? • transform energy • generate ATP • double membranes • semi-autonomous organelles • move, change shape, divide • internal ribosomes, DNA & enzymes

  26. Mitochondria • Almost all eukaryotic cells have mitochondria • Even PLANT CELLS!!! • # of mitochondria is correlated with aerobic metabolic activity • more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria?

  27. Plastids • Different Types: • amyloplasts • store starch in roots & tubers • chromoplasts • store pigments for fruits & flowers • chloroplasts • store chlorophyll & function in photosynthesis • in leaves, other green structures of plants & in eukaryotic algae

  28. Review: How are “Mito” and“Chloro” different? • Not part of endomembrane system • Grow & reproduce • Own ribosomes • Own circular chromosome • directs synthesis of proteins produced by own internal ribosomes Who else has a circular chromosome not bound within a nucleus? BACTERIA

  29. Endosymbiosis theory 1981 • Mitochondria & chloroplasts were once free living bacteria • engulfed by ancestral eukaryote • Endosymbiont • cell that lives within another cell (host) • mutualistic relationship • evolutionary advantage for both • one supplies energy • the other supplies raw materials & protection Lynn Margulis U of M, Amherst

  30. Endosymbiosis theory Evolution of eukaryotes

  31. Putting it all together, try labeling.. animal cells plant cells

  32. Any Questions??

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