Lipids and proteins are mobile, and can

diffuse laterally in the membrane

Saturated fatty acids are saturated with hydrogens which means

they have all single bonds

meaning of (n:x)

-n=

-x=

-number of carbons

-amount of double bonds

What is the structure of myristic acid?

(14:0)

What is the structure of palmitic acid?

(16:0)

What is the structure of stearic acid?

(18:0)

Unsaturated fatty acid have

double bonds

Oleic acid structure____

(18:1)

Linoleic acid structure ___

(18:2)

Arachidonic acid structure___

(20:4)

Δ^x

x means its the location of the double bonds

Double bonds are cis and

unconjugated

When unsaturated fatty acids have one or more unconjugated double bonds,

the fatty acid can not fully extend

Saturated chains optimally pack tightly and form

more stable, rigid, ordered aggregates

Unsaturated chains bend and pack in a less ordered way with greater potential

greater potential for motion

Higher order means more stability and higher

melting temperature, T_m

Triacylglycerols (TAG's) are considered to be

1. The most reduced form of carbon in nature (oxidation releases energy)

2. No solvation with water (dehydrated, weighs less)

3. Efficient packing (not just because dehydrated, also van Der Waals)

TAG's are a major

energy source for many organisms

Most fatty acids in plants and animals exist in the form of

triacylglycerols

If all fatty acids are the same, the molecule is called a

simple triacylglycerol

If two or three fatty acids are different, it is called

mixed triacylglycerols

a 1,2-diacylglycerol that has a phosphate group esterified at C3 of the glycerol backbone is a

glycerophospholipid

Glycerophospholipid are ____lipids and are essential components of cell membranes

structural

All head groups start with

-OH groups

Look at table 9-2

Phospholipases A₁ and A₂ cleave fatty acids from glycerophospholipids producing

lysophospholipids

Phospholipases C and D hydrolyze on either side of the phosphate in

the polar head group

Phospholipids play important roles such as

giving chemical signals in and on cells

Lipid signals act _______, and have short lifetimes

locally within or near the cell

Ether glycerophospholipids (PAF) properties:

1. a potential mediator in inflammation, allergic response, and shock

2. Has a beneficial effect on toxic shock syndrome

3. involved in implantation of the egg in the uterine wall

4. stimulates production of fetal lung surfactant

Sphingolipids are frequently present in

animal cell membranes

Has 18-carbon alcohol, forms the backbone of these lipids

sphingosine

A fatty acid that is joined to sphingosine is linked in

amide group and is called a ceramide

Are ceramides with one or more sugars in beta glycosidic linkage at the hydroxyl group

Glycosphingolipids

Glycosphingolipids with one sugar and a single sugar headgroup

cerebrosides

Glycosphingolipids with 3 or more sugars, and one of which is a sialic acid

Gangliosides

Sphingolipids increase T_m, and

pack together well

Terpenes are a class of lipids formed from combinations of

isoprene units

Isoprene units have two possible linkages

1) head-to-tail

2) tail-to-tail

Steroids are isoprene-based molecules built on a core structure of

three 6-membered ring and one 5-membered ring fused together

What is the most common steroid in animals and precursor for all other steroids?

Cholesterol

What are the functions of steroid hormones?

salt balance, metabolic and sexual function

Cortisol provides control of

carbohydrates, protein, and lipid metabolism

testosterone is

the primary male sex steroid hormone

Estradiol is

the primary female sex steroid hormone

Progesterone is a precursor of

testosterone and estradiol

Bile salts/acids including cholic and deoxycholic acid are

detergent molecules secreted in bile from the gallbladder

Are insoluble in water, and serve as water repellant

waxes

Classes of lipids

1. Triacylglycerols: energy storage; fats

2. Glycerophospholipids: structural and signaling

3. Sphingolipids: structural

4. sterols (terpenes): structural and signaling

Functions of membranes :

- barrier to toxic molecules

- Transport and accumulation of nutrients

- energy transduction

- facilitation of cell motion

-reproduction

- signal transduction

-cell-cell interactions

Biological membranes contain as much as ______% protein or as little as _____% protein

75-80%, 15-20%

Lipids self-associate to form membranes because of

hydrophobic effect

Lipids spontaneously form ordered structures in

water

What is the phospholipid bilayer?

fluid matrix

Two classes of proteins:

-peripheral proteins( extrinsic )

-integral proteins ( intrinsic )

Slow transverse diffusion of lipids and proteins ______. By contrast lateral diffusion is ______.

preserves membrane asymmetry, rapid

Bilayer core dimensions

Peripheral membrane proteins:

-can be dissociated with high salt concentration

- insert hydrophobic loop or amphiphilic alpha helix

- form ionic interactions and H bonds

Integral membrane proteins are strongly embedded in lipid bilayer and

-can be removed from the membrane by denaturing

- secondary structure neutralizes the highly polar N-H and C=O functions of the peptide backbone through H-bond formation

Transmembrane segment is alpha-helical and consists of

19 hydrophobic acids

Bacteriorhodopsin (bR) is found in ____ and consists of____

purple patches of Halobacterium, 7 transmembrane helical segments

The sequence of a transmembrane protein is adapted to the transition from water to the

hydrophobic core and then to water again

Trp, His, and Tyr are mixtures of

polar and non-polar parts

Each alpha helix requires____ per transmembrane strand. Each beta strand requires only ___ per transmembrane strand.

21-25, 9-11

Four types of lipid-anchored proteins:

1. Amide-linked myristoyl anchors

2. Thioester-linked fatty acid anchors

3. Thioether-linked prenyl anchors

4. Glycosyl phosphatidylinositol anchors

Amide-linked myristoyl anchors are always linked to the alpha-amino N of Gly residue and

always myristic acid and N-terminal

Thioester-linked and acyl anchors are always linked to Cys and

myristate, palmitate, stearate, and oleate

Ethanolamine link to an oligosaccharide linked in turn to

inositol of phosphatidyl inositol (PI)

Always attached to a C-terminal carboxyl group of a recognized sequence,

GPI-linked proteins are found on the cell surface where oligosaccharide links are found

Membranes are asymmetric structures

1. Lateral Asymmetry of Proteins

2. Lateral Asymmetry of Lipids

3. Transverse Asymmetry of Proteins

4. Transverse Asymmetry of Lipids

ATP flipases move PS from the

outer leaflets to the inner leaflets: "flip in"

ATP flopases move lipids including cholesterol, PC< and sphingomyelin from the

inner leaflets to the outer leaflet of the membrane: "flop out"