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The Cell

The Cell. AP Biology. The Cell Theory. 1. All organisms are made up of cells 2. The cell is the basic unit of structure and function in all organisms 3. All cells come from pre-existing cells. Underlying the diversity of life is a striking unity. Activities of life

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The Cell

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  1. The Cell AP Biology

  2. The Cell Theory 1. All organisms are made up of cells 2. The cell is the basic unit of structure and function in all organisms 3. All cells come from pre-existing cells

  3. Underlying the diversity of life is a striking unity

  4. Activities of life • Most everything you think of a whole organism needing to do, must be done at the cellular level… • reproduction • growth & development • energy utilization • response to the environment • homeostasis

  5. Types of Cells Prokaryotebacteria cells Eukaryoteanimal cells Eukaryoteplant cells

  6. Golgi mitochondria chloroplast ER Organelles • Specialized structures • specialized functions • 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

  7. What jobs do cells have to do? • building proteins • proteins control everycell function • make energy • for daily life • for growth • build more cells • growth • reproduction • repair

  8. proteins cells DNA organism Why study protein production?

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

  10. TO: TO: TO: TO: endoplasmicreticulum nucleus proteinon its way! DNA RNA vesicle vesicle ribosomes TO: protein finishedprotein Golgi apparatus Making Proteins

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

  12. Cells gotta live! ATP • What jobs do cells have to do? • make proteins • proteins control everycell function • make energy • for daily life • for growth • build more cells • growth • reproduction • repair

  13. Cells need power! • Making energy • take in food & digest it • take in oxygen (O2) • make ATP • remove waste ATP

  14. 1960 | 1974 Lysosomes Christian de Duve • Function • little “stomach” of the cell • digests macromolecules • “clean up crew” of the cell • cleans up broken down organelles • Structure • vesicles of digestive enzymes Where old organellesgo to die! only in animal cells

  15. Lysosomal enzymes • Lysosomal enzymes work best at pH 5 • organelle creates custom pH • how? • proteins in lysosomal membrane pump H+ ions from the cytosolinto lysosome • why? • enzymes are very sensitive to pH • why? • enzymes are proteins — pH affects structure • why is this an adaptation: digestive enzymes which function at pH different from cytosol? • digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself!

  16. 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 • ex: self-destruct of cancerous cell

  17. syndactyly 15 weeks Fetal development 6 weeks

  18. When things go wrong… • 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

  19. + From food to making Energy ATP • Cells must convert incoming energy to forms that they can use for work • mitochondria: from glucose to ATP • chloroplasts: from sunlight to ATP & carbohydrates • ATP = immediate energy • carbohydrates = stored energy ATP

  20. Lynn Margulis U of M, Amherst Mitochondria & Chloroplasts • Important to see the similarities • transform energy • generate ATP • double membranes = 2 membranes • semi-autonomous organelles • move, change shape, divide • internal ribosomes, DNA & enzymes

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

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

  23. Mitochondria are everywhere!! animal cells plant cells

  24. Cells gotta live! • What jobs do cells have to do? • building proteins • proteins control every cell function • make energy • for daily life • for growth • build more cells • growth • reproduction • repair

  25. Cytoskeleton • Function • structural support • maintains shape of cell • provides anchorage for organelles • protein fibers • microfilaments, intermediate filaments, microtubules • motility • cell locomotion • cilia, flagella, etc. • regulation • organizes structures & activities of cell

  26. Cytoskeleton • actin • microtubule • nuclei

  27. Centrioles • Cell division • in animal cells, pair of centriolesorganize microtubules • guide chromosomes in mitosis

  28. Cell Size

  29. Limits to cell size • Lower limit • smallest bacteria • mycoplasmas • 0.1 to 1.0 micron (µm = micrometer) • most bacteria • 1-10 microns • Upper limit • eukaryotic cells • 10-100 microns • micron = micrometer = 1/1,000,000 meter • diameter of human hair = ~20 microns

  30. What limits cell size? • Surface to volume ratio • as cell gets bigger its volume increases faster than its surface area • smaller objects have greaterratio of surface area to volume 6:1 ~1:1 6:1 s:v

  31. aa aa CH NH3 CHO CHO CO2 CO2 NH3 O2 O2 NH3 CO2 aa aa CH O2 Limits to cell size • Metabolic requirements set upper limit • in large cell, cannot move material in & out of cell fast enough to support life What process is this? aa O2 CH CHO CO2 aa NH3 CHO CH O2 aa What’s the solution?

  32. CO2 CO2 O2 NH3 aa NH3 CO2 NH3 CO2 CO2 NH3 O2 NH3 CO2 CO2 CO2 aa NH3 NH3 NH3 CHO CO2 CO2 aa CH How to get bigger? But what challenges do you have to solve now? • Become multicellular (cell divides) aa O2 CH CHO CO2 aa NH3 CHO CH O2 aa

  33. Phospholipid Cholesterol Membrane proteins Cell membrane • Exchange structure • plasma membrane functions as selective barrier • allows passage of O2 & nutrients IN • allows passage of products & wastes OUT

  34. Cell Membrane

  35. Overview • Cell membrane separates living cell from nonliving surroundings • thin barrier = 8nm thick • Controls traffic in & out of the cell • selectively permeable • allows some substances to cross more easily than others • hydrophobic vs hydrophilic • Made of phospholipids, proteins & other macromolecules

  36. Phosphate Phospholipids • Fatty acid tails • hydrophobic • Phosphate group head • hydrophilic • Arranged as a bilayer Fatty acid Structure and function relationship

  37. Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads

  38. More than lipids… • In 1972, S.J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer

  39. Glycoprotein Glycolipid Transmembrane proteins Peripheral protein Filaments ofcytoskeleton Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Extracellular fluid Phospholipids Cholesterol Cytoplasm

  40. Membrane fat composition varies • Fat composition affects flexibility • membrane must be fluid & flexible • about as fluid as thick salad oil • % unsaturated fatty acids in phospholipids • keep membrane less viscous • cold-adapted organisms, like winter wheat • increase % in autumn • cholesterol in membrane

  41. Membrane Proteins • Proteins determine membrane’s specific functions • cell membrane & organelle membranes each have unique collections of proteins • Membrane proteins: • peripheral proteins • loosely bound to surface of membrane • cell surface identity marker (antigens) • integral proteins • penetrate lipid bilayer, usually across whole membrane • transmembrane protein • transport proteins • channels, permeases (pumps)

  42. Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic

  43. Classes of amino acids What do these amino acids have in common? polar & hydrophilic

  44. Protein’s domains anchor molecule Polar areas of protein • Within membrane • nonpolar amino acids • hydrophobic • anchors protein into membrane • On outer surfaces of membrane • polar amino acids • hydrophilic • extend into extracellular fluid & into cytosol Nonpolar areas of protein

  45. Porin monomer H+ Retinal chromophore b-pleated sheets NH2 Bacterial outer membrane Nonpolar (hydrophobic) a-helices in the cell membrane COOH Cytoplasm H+ Examples water channel in bacteria proton pump channel in photosynthetic bacteria function through conformational change = shape change

  46. Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Enzymeactivity Cell surfacereceptor Cell adhesion Cell surface identity marker Attachment to thecytoskeleton

  47. Membrane carbohydrates • Play a key role in cell-cell recognition • ability of a cell to distinguish one cell from another • antigens • important in organ & tissue development • basis for rejection of foreign cells by immune system

  48. Movement across the Cell Membrane

  49. Diffusion • 2nd Law of Thermodynamicsgoverns biological systems • universe tends towards disorder (entropy) • Diffusion • movement from high  low concentration

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