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Chapter 3

Chapter 3. Part 2. This chapter contains a lot of chemistry. Read your textbook!!! Find your biology 1107 textbook or cell biology textbook and read about membranes Look at your organic chemistry/chemistry textbooks Read about esters, ethers, glycerol and phospholipids.

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Chapter 3

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  1. Chapter 3 Part 2

  2. This chapter contains a lot of chemistry • Read your textbook!!! • Find your biology 1107 textbook or cell biology textbook and read about membranes • Look at your organic chemistry/chemistry textbooks • Read about esters, ethers, glycerol and phospholipids

  3. Look at chapter 3 chemistry worksheet

  4. Outline • Membrane structure • Basic backbone • Differences between eukaryotes and prokaryotes • What is different about archae? • Membrane function • Transport mechanisms

  5. Membranes • Get together with a partner(s) • Draw a membrane • Include 3 of the 4 class of molecules in nature • What is on the outside? • What is one the inside? • Or, inbetween? • How is a eukaryotic membrane diff. from prokaroytic? • What is the function(s) of a membrane?

  6. Membrane lipids • Sterols • Rigid, planar lipids found in eukaryotic membranes • Strengthen and stabilize membranes • Hopanoids • Structurally similar to sterols • Present in membranes of many Bacteria • a a = sterol (cholesterol) b = hopanoids

  7. Phospholipids • H2C-OH • HC-OH Glycerol • H2C-OH • In phospholipids, two of the OH groups are linked to fatty acids and one of the OH groups is linked to a phosphorylated alcohol • Fatty acids have a carboxyl group with long hydrocarbon tails

  8. Ester linked phospholipid (bacteria and eukarya) Polar headglycerol Nonpolar tailfatty acid Archaea contain ether-linked lipids Phospholipid Backbone

  9. glycerol ester link R=fatty acid (saturated or unsaturated) Bacterial /Eukaryotic membranes

  10. Archae are different from eukarya and bacteria • Ether linkage between glycerol and hydrophobic side chains • Instead of fatty acids, they have side chains composed of the 5C hydrocarbon isoprene • extra CH3 group

  11. Archaeal Membranes • Ether linkages in phospholipids • Different from Bacteria andEukarya that have ester linkages in phospholipids • Archaeal lipids lack fatty acids, have isoprenes instead • Major lipids are glycerol diethers

  12. Glycerol diether Contains phytanyl 4 linked isoprene units (5 carbons) Two types of lipids in archaeal membranes

  13. Two types of lipids in archaeal membranes • Diglycerol tetraether • Contains 2 phytanyl groups linked together

  14. Archaea membrane lipids

  15. Archaea Lipid Structure • Glycerol diether (phytanyl) forms a bilayer • Diglycerol tetraether (biphytanyl) forms a monolayer

  16. Questions on Membrane lipids

  17. Membrane transport systems • Simple transporters • Phosphotransferase-type transporters (group translocation) • ABC (ATP-binding cassette) transporters • All require energy in some form, usually proton motive force or ATP

  18. Membrane transport systems

  19. Transport proteins = carrier proteins Enery or no energy 1 or 2 molecules Simple transport

  20. Proton motor force (PMF) drives transportin symport or antiport • protons concentrated on outside of cell generates potential energy • Protons (H+) move from high to low energy • Energy released used to drive the movement of another molecule from low to high energy

  21. H+ goes from high to low concentration while another molecule goes from low to high concentration

  22. Next group of transporters = group translocation • Phosphotransferase-type transporters • the transported substance is chemically altered during transport • Examples: glucose, • mannose and fructose • Enzymes are first phosphorylated • Then sugars are phosphorylated during transport • Energy derived from PEP

  23. Last transporters = Periplasmic binding proteins and ABC transporters • Periplasm found in gram – bacteria • Contains numerous proteins involved in transport

  24. 3 parts Periplasmic binding protein Membrane spanning transporter ATP hydrolyzing protein ATP binding cassette

  25. ABC: ATP Binding Cassette • Binding protein • Extremely high affinity for substrate • Uptake of nutrients in really low concentration (EX. Maltose) • Gram – cells: periplasmic protein and is mobile • Gram + cells: membrane spanning protein and is attached • Transporter • Membrane spanning • ATP hydrolyzing protein • Spans membrane and extends into cytoplasm • ATP provides energy for transport

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