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Cell Structure

Cell Structure . And Function. Why are cells small?. Metabolism determines size. Adequate surface area for exchange of materials. Surface-area-to-volume ratio. Volume grows faster then surface area. In larger cells, rates of exchange are inadequate to maintain cell. .

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Cell Structure

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  1. Cell Structure And Function

  2. Why are cells small? • Metabolism determines size. • Adequate surface area for exchange of materials. • Surface-area-to-volume ratio. • Volume grows faster then surface area. • In larger cells, rates of exchange are inadequate to maintain cell.

  3. Prokaryotic Cells Vs. Eukaryotic Cells • Prokaryotic Cells- lack a membrane bound nucleus, and they are small (1-10um in diameter). • Eukaryotic Cells-have membrane bound nucleus, and they are larger (10-100um in diameter).

  4. Prokaryotic Cells • There are two groups: • Domain Bacteria • And • Domain Archaea

  5. Plasma Membrane • Regulates the movement of molecules.

  6. Prokaryotic Cells • Thylakoids • Chlorophyll • Cell wall-> polysaccharides & proteins. • Plasma membrane -> glycerol+hydrocarbons • DNA&RNA base similar to eukaryotes • They live in extreme habitats.

  7. Prokaryotic ->Eukaryotic Cells • Endosymbiotic Theory= Cells living with in cells, in a mutually benificial relationship. (Symbiosis:)). • Organelles have own DNA • Organelles divide independently of the cell they live in. • Double membrane.

  8. Eukaryotic Cells • Animal & Plant Cells

  9. The Nucleus • It is the command center. • It has chromatin in it -forms chromosomes -DNA+RNA+protein • Nucleolus: -produces ribosomes • Nuclear Envelope: -Double membrane

  10. Ribosomes: Protein Synthesis • Occur in Cytoplasm or attached to endoplasmicreticulum.

  11. Rough Endoplasmicreticulum • Rough ER • Continuous with nuclear envelope • Flattened saccules • Ribosomes • Synthesizes proteins • Modifies proteins: -adds sugar chains -helps with folding -forms transport vesicles

  12. Smooth Endoplasmic Reticulum • Smooth ER -continuous with rough endoplasmic reticulum -tubular -no ribosomes -main functions: 1.)synthesizes lipids (including sex hormones) 2.) detoxifies drugs -forms transport vesicles

  13. GolgiApparatus • -stack of curved or flattened saccules • -inner vs outer face • -main functions: • Modify ER products • Manufacture Macromolecules • Sort Products • Ship products to vesicles

  14. Endomembrane System • Consists of: Nuclear envelope • -Endoplasmicreticulum • -Golgi Appartus • -Lysosomes • -Vesicles Importance: • - enzymes in certain areas • -vesicles move molecules around

  15. Lysosomes • Produced by Golgi Apparatus in animal cells • Low pH • Digestive enzymes-> hydrolyze macromolecules • Apoptosis- cell death

  16. Peroxisomes • Vesicles that contain enzymes. • Enzymes synthesized in cytoplasm( not in ER) • Produce H2O2 ( by product), then water. • In seedlings, convert fatty acid to sugars • In liver, detoxify ETOH (jack daniels)

  17. Energy Transformers of Cells • Mitochondria: Cellular respiration-> ATP • Chloroplasts: Photosynthesis->Carbohydrates

  18. Vaculoles • Store substances • Plant cell central vacuole: Cell support Stores nutrients and waste products Acts like lysosomes in animals Pigments are stored Plant cell growth

  19. Mitochondria • Cristae Increase surface area (enzyme attachment) • Matrix contains enzymes->cellular respiration.

  20. Cytoskeleton • What is it?? • Networks of fibers that run through the cytoplasm. • What does it do? • Mechanical support • Maintain cell shape • Anchor organelles • Enables cells to change shape • Entire cell • Organelles with in cell wall

  21. Cell Membrane Structure and Function • Fluid Mosaic Model -1972 Singer and Nicholson • Plasma membrane is a mosaic of protein molecules bobbing in a fluid layer of phospholipids.

  22. Regions of Integral Proteins • Hydrophobic Regions: Not water friendly • Hydrophilic: Water lover

  23. Functions of Cell Membrane • Barrier between living contents & surrounding environment. • Regulates what goes in and out of cell • It is selective • It helps maintain homeostatic environment.

  24. Fluid mosaic model • Proteins in membrane can be: • -peripheral-> inside surface anchored by cytoskeleton(structural role) • -integral->imbedded in membrane but can move laterally. • Most proteins move laterally in membrane.

  25. Fluid Mosaic Model • Carbohydrate Chains • Glycolipid=phospholipid+carbohydrate (sugar chain) • Glycoprotein=protein+carbohydrate (sugar chain). • Asymmetry-> • Carbohydrate chain on outside surface BLOOD TYPE BASED ON CARBOHYDRATE CHAINS A,B,O

  26. Fluidity of Cell Membrane • Body temperature->olive oil • More unsaturated fatty acid residues, greater fluidity. • Cholesterol (animal cells) stiffens and strengthens membrane • Why is it good to be fluid? • Proteins only function properly when they can move

  27. Channel Protein • Allows particular molecules to cross cell membrane freely. • Cystic Fibrosis->faulty chloride channel

  28. Carrier Protein • Selectively interacts with a specific molecular ion so that it can cross plasma membrane. • Obesity-> problem with sodium-potassium transport

  29. Enzymatic Protein • Carry out metabolic reactions • Adenylate cyclase->ATP • Metabolism • Toxin of cholera bacteria disrupts adenylate cyclase-> severe diarrhea

  30. Permeability of Plasma Membrane • It is differentialy (selectively) permeable.

  31. How do molecules cross membrane? • Passive Transport: DOES NOT REQUIRE ATP!!! • Active Transport: REQUIRES LOTS OF ATP!!!!

  32. What is Diffusion? • Movement of molecules from a high concentration to a lower concentration until equilibrium is achieved. • Movement down a concentration gradient.

  33. What is Osmosis? • Diffusion of water across a differentially permeable membrane due to concentration differences. • Solution=fluid(the solvent) That contains a dissolved solid(the solute)

  34. Transport Across Membrane:passive transport->diffusion • Co2, O2,glycerol,water, alcohol Diffuse across membrane

  35. Transport across membrane: passive transport-> facilitated • Moves molecules from high concentration to low concentration. • Sugars and amino acids (non-lipid soluble). • Requires carrier protein • No energy expenditure needed • Are specific • Undergo change in shape

  36. Transport across membrane: Active Transport • Move molecules across concentration gradient • Requires energy (ATP)& carrier proteins • Proteins are called Pumps

  37. Active Transport: Exocytosis • Secretion- moving out of cell

  38. Active Transport: Endocytosis • Endocytosis= taking substance into cell by vesicle formation

  39. Active Transport: Endocytosis • Phagocytosis= cellular eating, engulfing of large particles • Pinocytosis= cellular drinking engulfing of lliquid and small particles • Receptor-Mediated Endocytosis=form of pinocytosis that is specific, this si how cells can bring in a bulk qty of molecules.

  40. Modification of Animal Cell: Surface Extracelluar matrix • ECM functions: • Support cell and influence behavior • Components:protein+polysacharides • Structural proteins= • Collagen and elastin-> • Strength and resiliance • Adhesive proteins = • Fibronectins and laminins -> • Cell migration and communication

  41. Modification of Plant Cell Surface:Cell Wall • Functions : • Protection • Maintain shape • Prevent excessive water uptake • Hold plant up • Cellulose+other polysaccharides+proteins

  42. Modification of Plant Cell Wall Surface: Cell Wall • Primary cell wall->young cell-> cellulose +pollysaccharides) • Middle Lamella->cement cells together w/ pectin • Secondary cell wall ->strength(lignin) • Plasmodesmata-> cytoplasmic connections

  43. Metabolism: Energy and Enzymes • What is metabolism? • All chemical reactions that occur in a cell

  44. What is energy? • Capacity to do work and bring about change

  45. Different Kinds of Energy • Kinetic=energy of motion • Potential= stored energy

  46. Why are we talking about energy? • 1.cells must acquire energy from environment • 2.cells can not make energy (energy exists and can be transformed) • 3in life energy transformations are chemical

  47. Different Kinds of Energy • Food has potential energy-> Kinetic energy • Food= Chemical energy • Energy flows it does not cycle

  48. Laws of Thermodynamics • 1st law of thermodynamics: law of conservation of energy. • Energy can not be created nor destroyed but it can be changed from one form to another

  49. Laws of Thermodynamics • 2nd Law of Thermodynamics: • Energy can not be changed from one form to another with out a loss of useable energy

  50. Law of Thermodynamics • 2nd law (restated): • Every energy transformation makes the universe more disordered. • Entropy is a measure of disorder or randomness

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