Transcript 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 Look at chapter 3 chemistry worksheet Outline • Membrane structure • Basic backbone • Differences between eukaryotes and prokaryotes • What is different about archae? • Membrane function • Transport mechanisms 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? Membrane lipids – Sterols • Rigid, planar lipids found in eukaryotic • a membranes • Strengthen and stabilize membranes – Hopanoids • Structurally similar to sterols • Present in membranes of many Bacteria a = sterol (cholesterol) b = hopanoids Phospholipids • H2C-OH • HC-OH • H2C-OH Glycerol • 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 Phospholipid Backbone • Ester linked phospholipid • Archaea contain ether(bacteria and eukarya) linked lipids – Polar headglycerol – Nonpolar tailfatty acid Bacterial /Eukaryotic membranes • glycerol ester link • R=fatty acid (saturated or unsaturated) 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 Archaeal Membranes – Ether linkages in phospholipids – Different from Bacteria and Eukarya that have ester linkages in phospholipids – Archaeal lipids lack fatty acids, have isoprenes instead – Major lipids are glycerol diethers Two types of lipids in archaeal membranes • Glycerol diether – Contains phytanyl – 4 linked isoprene units (5 carbons) Two types of lipids in archaeal membranes • Diglycerol tetraether – Contains 2 phytanyl groups linked together Archaea membrane lipids Archaea Lipid Structure • Glycerol diether (phytanyl) forms a bilayer • Diglycerol tetraether (biphytanyl) forms a monolayer Questions on Membrane lipids 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 Membrane transport systems Simple transport • Transport proteins = carrier proteins • Enery or no energy • 1 or 2 molecules Proton motor force (PMF) drives transport in 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 H+ goes from high to low concentration while another molecule goes from low to high concentration 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 Last transporters = Periplasmic binding proteins and ABC transporters • Periplasm found in gram – bacteria • Contains numerous proteins involved in transport ATP binding cassette • 3 parts • Periplasmic binding protein • Membrane spanning transporter • ATP hydrolyzing protein 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