Presentation is loading. Please wait.

Presentation is loading. Please wait.

Lipids Highly diverse structures Unifying property Hydrophobic: little to no affinity to water Contains hydrocarbons, which form nonpolar covalent bonds.

Similar presentations


Presentation on theme: "Lipids Highly diverse structures Unifying property Hydrophobic: little to no affinity to water Contains hydrocarbons, which form nonpolar covalent bonds."— Presentation transcript:

1 Lipids Highly diverse structures Unifying property Hydrophobic: little to no affinity to water Contains hydrocarbons, which form nonpolar covalent bonds Do not form polymers Biologically important lipids containing molecules: –Fats –Phospholipids –Steroids

2 Fats Structure –Composed of two different molecules bonded by ester linkage fatty acid & glycerol –- Fatty acid Hydrocarbon chain with a carboxyl group at one end –Glycerol Three-carbon alcohol –Each carbon attached to hydroxyl group Try to Draw

3 LE 5-11a Dehydration reaction in the synthesis of a fat Glycerol Fatty acid (palmitic acid)

4 LE 5-11b Ester linkage Fat molecule (triacylglycerol)

5 Hydrophobic H 2 O molecules form hydrogen bonds with each other and EXCLUDE fatty acid chains--> Fats separate from H 2 O (like oil & vinegar) Properties of Fats Fatty acids variable chain length (often carbons)

6 Saturated fat - refers to saturated fatty acid chains - carbons contains maximum number of hydrogens - results in 100% single bonds (no double bonds) - more linear, packs tightly to form solid Tend to be from animals

7 LE 5-11b Ester linkage Fat molecule (triacylglycerol) Saturated or unsaturated?

8 LE 5-12a Saturated fat and fatty acid. Stearic acid Butter

9 Unsaturated fat - contains unsaturated fatty acids -carbon-carbon double bonds (>1) -irregular hydrocarbon conformation -poor packing -forms liquids (oils) at room temperature Tend to be from plants and fish

10 LE 5-12b Unsaturated fat and fatty acid. Oleic acid cis double bond causes bending Olive oil Other liquid fats (unsaturated)?

11 Phospholipids Structure –two fatty acids bonded to glycerol through ester linkage –Phosphate bonded to third hydroxyl group of glycerol Fatty acids= Hydrophobic tail Phosphate and other groups= hydrophilic head Draw schematic

12 LE 5-13 Structural formula Space-filling model Phospholipid symbol Hydrophilic head Hydrophobic tails Fatty acids Choline Phosphate Glycerol Hydrophobic tails Hydrophilic head

13 If many phospholipids were mixed in H 2 O into what structures would they self-assemble? 1.Micelle (draw) - Detergents 2.Bilayer (draw) -Cell membranes

14 LE 5-14 WATER Hydrophilic head Hydrophobic tails WATER Cellular membrane: Phospholipid Bilayer

15 Steroids Structure - Hydrophobic molecules made of 4 fused hydrocarbon rings Examples and Diverse Functions –Cholesterol Component of animal cell membranes Building block for steroid sex hormones such as –Estrogen, testosterone, progesterone High levels--> contribute to heart disease

16 Cholesterol

17 estradiol testosterone

18 Pardon me. Did you miss anything?

19 Ch 7 Membrane Structure and Function

20 - Boundary between intracellular compartments, living cells, and abiotic environment –Selectively permeable –Some molecules cross membranes more readily than others Cellular membrane -overall functions

21

22 Predominant constituent: phospholipids Amphipathic molecules: hydrophobic AND hydrophilic Membrane Structure Dispersed protein components Membrane organization and properties described by: Fluid Mosaic Model Singer and Nicolson 1972

23 LE 7-2 Hydrophilic head Hydrophobic tail WATER Organization of membrane phospholipids

24 Mosaic: something made of small pieces

25 LE 7-3 Hydrophilic region of protein Hydrophobic region of protein Phospholipid bilayer Mosaic: Proteins dispersed among phospholipids in membrane:

26 Freeze-fracture studies of the plasma membrane Frozen membrane split along the middle of the phospholipid bilayer using a knife Imaged by EM Supports mosaic part of model

27 LE 7-4 Knife Cytoplasmic layer Extracellular layer Cytoplasmic layer Plasma membrane Extracellular layer Proteins

28 The Fluidity of Membranes Phospholipids move laterally within the bilayer Some membrane proteins also drift laterally Rarely does a phospholipid flip-flop transversely across the membrane

29 LE 7-5a Lateral movement (~10 7 times per second) Flip-flop (~ once per month) Movement of phospholipids

30 Cool temp: membranes switch from fluid to more solid state Solidification depends on type of lipid What property of lipids would favor liquid versus solid state? Effects of Temperature on membranes

31 LE 7-5b Viscous Fluid Unsaturated hydrocarbon tails with kinks Membrane fluidity Saturated hydro- carbon tails Degree of saturation of fatty acid tails

32 Tends to moderate effects of temp. on membrane state At warm temperatures (such as 37°C), restrains movement of phospholipids At cool temperatures, maintains fluidity by preventing tight packing Steroid cholesterol also component of membranes

33 LE 7-5c Cholesterol Cholesterol within the animal cell membrane

34 Can drift within the bilayer –Proteins much larger than lipids--> move more slowly Cell fusion studies support fluidity of membrane proteins Movement of membrane proteins

35 LE 7-6 Membrane proteins Mixed proteins after 1 hour Hybrid cell Human cell Mouse cell

36 Membrane Proteins and Their Functions Proteins determine most of the membrane’s specific functions Peripheral membrane proteins –not embedded –attached to extracellular or cytoplasmic surface Integral membrane proteins –penetrate the hydrophobic core of bilayer –often span the membrane

37 LE 7-7 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Microfilaments of cytoskeleton Cholesterol Integral protein Peripheral proteins CYTOPLASMIC SIDE OF MEMBRANE EXTRACELLULAR SIDE OF MEMBRANE Glycolipid


Download ppt "Lipids Highly diverse structures Unifying property Hydrophobic: little to no affinity to water Contains hydrocarbons, which form nonpolar covalent bonds."

Similar presentations


Ads by Google