Chapter 8: Lipids and membranes Flashcards
Criteria to classify a compound as a lipid
a. They lack a common functional group
b.** Water-insoluble bio-compounds **
c. Some contain polar neutral or polar charged groups;
d. The bulk of their structure is hydrocarbon-like
Fatty acids
Properties
i. Fatty acids can be saturated with hydrogens
ii. They are carboxylic water
iii. They are soluble in water/fat
Fatty acids
Classification based on absence or presence of double bonds
i. They have an even number of carbons; ranging from 12 -24. The acidic group is used to add carbons, which is why they are even.
ii. F.A can be saturated with hydrogens
iii. F.A can be monounsaturated or polyunsaturated
iv. Double bonds are usually in the cis formation
v. Those without double bonds are known as straight chains.
vi. Double bonds kink the acyl chain preventing the efficient packing with neighbors
1. Also referred to as a fatty acyl chain
Fatty acids
Identify omega fatty acids
i. The last carbon from the fatty acid chain is referred to as the omega.
ii. We cannot make omega 3 naturally so we need to consume it through our diet
Triacylglycerols
Other names
Can also be called fats and oils
Triacylglycerols
Components
They are made up of glycerol and 3 fatty acyl groups
Triacylglycerols
Identify ester linkages
- The alcyl groups of three fatty acids are esterified to the three hydroxyl groups of glycerol.
Triacylglycerols
Distinguish fats and oils and their origin and properties
i. Fats are solid at room temperature2/3 or 3/3 are saturated. High bp and mp
ii. Oils are liquid at room temperature. 2/3 or 3/3 unsaturated. Low bp
Glycerophospholipids
Identify them
i. Have polar charged head groups. Made of phosphate and aa
Glycerol attached to acyl group
ii. They are amphipathic. Suitable for being in the membrane to form lipid bilayers
Glycerophospholipids ? Identify individual components
ii. The black is the back bone and template. There are only two fatty acids.
**iii. Missing two other components ** look through the text
Glycerophospholipids
Specificity of phospholipases
i. Phospholipases cleave glycerophospholipids at specific sites
ii. They are specific enzymes that cleave.
Sphingolipids
Identify them
i. They are the backbone is sphingosine
ii. They replace glycerol in other amphipathic molecules
Sphingolipids
Identify individual components
i. Have a polar head known as phosphocholine. Those that are not sugars are known as sphingomyelin
1. Some of the sphingolipids have monosaccharides as head groups. The name is cerebroside
a. There is no phosphate group
b. It can still be found in the membrane because it is still polar even though it is not charged.
2. Other have oligosaccharides as head groups. Known as the ganglioside
ii. It has two hydrophobic tails.
Sphingolipids
Identify linkages in them
Amide bond- 2nd fatty acyyyl group
Phosphodiester bond
Sphingolipids
Distinguish cerebrosides and gangliosides
Cerebrosides are sphingolipids that contain a sugar unit. The sphingolipids called gangliosides are more complex, usually containing a branched chain of three to eight monosaccharides and/or substituted sugars
Cholesterol
Structure and properties
i. It is stored in the membrane and reduces its fluidity. Without it the bilayer will be very wobbly. Not amphipathic because the polar OH does not do much
ii. The most common is steroids
iii. The precursor to all other steroids
iv. Found in all animal cells
v. Takes 30 steps to make cholesterol
vi. It is flat and it can be inserted between the fatty tails near the head.
Waxes
Components and function
i. Esters made of a fatty acid and a very long alcohol
ii. Function as waterproofing agents
Lipids bilayer
Structure and properties
i. An array of amphipathic molecules whose tails associate with each other, out of contact with water, and whose head groups interact with water.
ii. It is a fluid structure
iii. There needs to be two hydrophobic tails. They are flexible and mobile
Membrane proteins
types
i. Integral membrane protein: more common
1. Pores, pumps, channels
2. Need to be hydrophobic non polar
3. Single helix can exist as an integral membrane protein. It cannot exist as a beta
4. 7 helix’s: 7tm
ii. Peripheral membrane protein
iii. Lipid linked protein: 3rd common
1. They anchor to the lipid bilayer
Membrane proteins
Properties
i. A membrane spanning alpha helix
ii. Membrane proteins can span the bilayer
1. Beta barrel
a. The longer they are they have a right-handed curvature
b. It allows things to move through
c. More suitable for receptors
2. Bacteriorhodopsin
