Class 14 - Lipids and Membrane Flashcards
Contrast fats with phospholipids and sterols in the body
fats are the principal stored forms of energy in many cells
phospholipids and sterols are the major structural elements of biological membranes
What are fatty acids?
aliphatic (forms open chain and not aromatic) hydrocarbon chains with a methyl at one end and a carboxyl group at the other end
How are fatty acids numbered?
- Numbering starts at the carboxyl group and goes to end
- Greek letters start with carbon next to carbonyl group and goes to the end
Methyl carbon at end of chain is always called w(omega) -carbon regardless of chain length
How many carbons do most fatty acids in the body have?
most have 16-20 carbons
Unsaturated vs saturated fatty acids
saturated fatty acids have all single bonds
unsaturated fatty acids have 1 or more double bonds which are in the cis transformation results in a bend/kink in the hydrocarbon chain
How are the polyunsaturated fatty acids seperated?
unsaturated fatty acids can have 1 or more double bonds
unsaturated with 1 double bond
double bond makes bend
polyunsaturated bonds
the double bonds are separated by a methylene group (CH2)
Compare the fatty acid delta vs omega nomenclature?
delta nomenclature (C18:1,delta^9)
number of carbons starts at carbonyl to first carbon in the double bond
number of double bonds after :
omega nomenclature (C18:1,omega^9)
Numbering of carbons starts from methyl omega end to the first carbon in the double bond closest to the methyl end
Explain the delta and omega on this molecule
What are essential fatty acids? What are the 2 omegas we know of?
Essential fatty acids are fatty acids that humans MUST get from their DIET because the body cant make them
Omega-3 in fish
Omega 6 in nuts
How do omega-3 and omega-6 differ?
omega-3 are fatty acids with at least a double bond in the 3rd carbon from the omega methyl end
- There are omega-3 with many double bonds
omega-6 are fatty acids with at least a double bond in the 6th carbon from the omega methyl end
– There are omega-6 with many double bonds
What conformation are the double bonds in the fatty acids?
cis conformation
Trans fat (trans-fatty acid) vs fatty acids (sat und unsat)
trans fats / trans-fatty acid have unsaturation but no bend in the molecule because it is trans configuration
unsaturated fatty acids have a bend where the double bond is and has a cis configuration
**They are structurally similar but the trans/cis configuration is important
saturated fatty acids have no double bond and no bend
Where do natural vs artificial trans fats / trans-fatty acids come from?
Natural - produced in the gut of some animals and foods made from these animals (meat, milk) and may contain small quantities of these fats
Artificial - created in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid (hydrogenates them)
What happens to hydrogenation of unsaturated fatty acids – how does that relate to trans fats?
food industry tried to create saturated fatty acids (from unsaturated molecules) that were more firm for processes foods
consequences
1. some have complete chemical hydrogenation
2. others have side effect of chemical hydrogenation where the double bond is in trans
What are other names for trans fat?
trans-fatty acid
partially hydrogenated cells
What do HDL do in the body?
trans fats DECREASE good HDL cholesterols
HDL: high density lipoproteins
- HDL picks up excess cholesterol and transports back to bodys liver for processing
What do LDL do in the body?
trans fats INCREASE bad LDL cholesterols
LDL: low density lipoproteins
- LDL transport cholesterol throughout the body and as it builds up in the walls of the body arteries the arteries become narrow and hardened
- reduces blood flow and leads to chance of stroke and heart attack
Rank the trans fat in vegetable oil to shortening
What are triglycerides and what do they do?
lipids with 1 glycerol molecule bonded with 3 fatty acids (most contain 2 or more diff fatty acids)
they function to provide stored energy, define body shape, insulate body from temperature changes, protect internal organs against physical shock
How are triglycerides formed?
a condensation reaction (H on the glycerol and the OH on the fatty acid chains) react in a condensation (dehydration) reaction to link fatty acids to glycerol
a covalent ester bond forms between the carboxyl group of one fatty acid and of one of the hydroxyl groups of the glycerol
What are the 2 major classes of lipids
Storage lipids (neutral) –> triglycerols
membrane lipids (polar) –>
phospholipids and glycolopids
What are the sub groups in phospholipids and glycolipids?
phospholipids -
glycerophospholipids –2 fatty acids, PO4, alcohol
sphingolipids - fatty acid, PO4, choline
glycolipids
sphingolipids - fatty acid, mono or oligosaccharide
