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 membranes Strengthen and stabilize membranes –Hopanoids Structurally similar to sterols Present in membranes of many Bacteria a a = sterol (cholesterol) b = hopanoids

Phospholipids H 2 C-OH HC-OH Glycerol H 2 C-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

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

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 CH 3 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