Chapter 10: Lipids and Transport Systems

Cholesterol

A type of fat made by the body from saturated fat; a minor part of fat in foods, Cholesterol intercalates between lipid membrane, which prevent FAs from getting too close helps to stabilize the structure of the plasma membrane., very hydrophobic except for the OH group. Structure is a carbon chain , with rings

Unsaturated Bonds

Contain double bonds that create kinks in lipids -Kinks creates bends reduce non-covalent interactions

Which of the following statements about biological membranes is FALSE? They are often organized into smaller regions of specific function. Phospholipids often require a specialized enzyme to facilitate movement across (flipping) the membrane. The faces of biological membranes are distinct and usually different in both composition and structure. Lipids and proteins move laterally at approximately the same rate within the membrane. They are composed of a mixture of lipids and proteins in which lateral diffusion of components is possible.

Lipids and proteins move laterally at approximately the same rate within the membrane.

melting point trends in lipids

Longer, saturated chains are gonna have a higher melting point as opposed to shorter unsaturated w/ more double bonds, more double bonds = dec in melting temp

Glycerolphospholipids

Made up of glycerol backbone, 2 fatty acid chains, and a phosphate group attached to some other molecule; most-common lipid found in membranes, variety in the R3 group (amide, acid, etc..) Glycerol is not chiral, but when you add a phosphate group it does form a stereocenter More hydrophillic than triglyceride because of the charged phosphate

Membrane proteins often have unique characteristics relative to globular proteins that function in largely aqueous environments. Which of the following does NOT describe a trait of a membrane protein? They can form membrane receptors, such as integrins (or LDL receptor), located on the surface of cells. They often have high hydrophobic content. Membrane proteins typically have hydrophilic residues situated on the surface in contact with membrane lipids and hydrophobic residues buried in the interior of the protein core. They can often contain common motifs, such as seven transmembrane α-helical proteins or β-barrels.

Membrane proteins typically have hydrophilic residues situated on the surface in contact with membrane lipids and hydrophobic residues buried in the interior of the protein core.

Amphatic

Molecules that have both polar and nonpolar ends are known as amphipathic like Lipids

Phase Transition

Normally the lipid bilayer is a dynamic fluid structure but if we cool it below the transition temp, it becomes more solid/gel like where the FAs become extend and more hydrophobic Carriers proteins can be slowed down in a solid gel, the transition temp depends on the saturated, length of chains, etc.

Differences at 25 versus 37

The membranes of cells grown at 25 °C would have (i) shorter fatty acids with (ii) a greater number of cis- double bonds compared to the membranes of cells grown at 37 °C.

Integral membrane proteins can be inserted into the membrane and folded into the normal 3D structure during translation. True False

True

Ceramides

Waxy lipid molecules important to barrier function and water-holding capacity; has a sphingosine except there's a hydrocarbon group attached to the amide group, but still one fatty acid chain

The abbreviated name below is short for which of the following biologically important fatty acids? 18:3cΔ9,12,15 all-cis-9,12,15-Eicosatetraenoic acid all-cis-9,12,15-Octadecatrienoic acid cis,cis,trans-9,12,15-Octadecatrienoic acid cis,cis,trans-9,12,15-Eicosatetraenoic acid

all-cis-9,12,15-Octadecatrienoic acid

Triglycerides

an energy-rich compound made up of a single molecule of glycerol joined by three molecules of fatty acid via ester linkage -Carboxylic group has turned into a gylcerol making it more hydrophobic than FAs -FAs chains can have variety(# of Cs, saturated vs unsat...) -Most abundant lipiid than can form bigger or smaller droplets -Can store a lot of energy since you don't need water

Naming Fatty Acids

chain length(start with carboxylic carbon):number of cis double bonds (A^where the double bonds are located)

Saturated Fats

fats that are solid at room temperature, more stable, no double bonds, a lot of non-covalent interactions to keep it stable (van der walts)

Saturated fatty acids are different than unsaturated fatty acids because they: have no C=C double bonds. exhibit free rotation about the carbon carbon bonds in the hydrocarbon tail. mostly have cis double bonds . have an even number of carbon atoms. have short hydrophobic tails.

have no C=C double bonds.

Spingolipids

membrane lipid, can hold one fatty acid + one fatty amine (sphingosine- 3 carbon chain, with an amide group attached), no glycerol backbone

peripheral membrane proteins

proteins associated with but not embedded within the plasma membrane, can directly or indirectly via interactions with integral membrane proteins or lipid anchored,one portion anchored in the membrane.

fatty acids

simplest lipid, Carboxylix acid (polar head) on one end connected to a chain of hydrocarbons which forms the hydrophobic tail, poorly soluble in water, even number of carbons

intergral membrane proteins

span the entire phospholipids bilayer, have 3 segments one portion that makes contact outside, one potion spans hydrophobic center, one spans the inside membrane Beta Sheets-don't have intramolecular binding, so they need ti have another sheet to create a beta barralel, where the inside is hydrophobic to allow things to pass through the membrane (like water and small polar molecules) outisde is hydrophillic α-helices are most commonly observed in transmembrane protein sequences when the distance from one side of a membrane to the other can be spanned by significantly fewer amino acids in a β-strand conformation. The helical conformation spanning the bilayer satisfies all the main-chain H-bond donors and acceptors within the helix, whereas the strand would be unable to form intramolecular H-bonds to satisfy it.

micelles

tiny spherical complexes of FA's that form when exposed to water, because therer's one polar end and hydrophobic end that bonds together as opposed to the phospholipids that form a lipid bilayer