Lipids Flashcards
(37 cards)
What defines lipids?
Their hydrophobicity.
How do you dissolve lipids?
Organic solvent - 2:1 mixture of chloroform and ethanol.
What are the biological functions of lipids?
- Energy storage (EX: TAG)
- Membrane structure (EX: phospholipids and sterols)
- Signal transduction (EX: steroid hormones)
- Enzyme cofactors (EX: Coenzyme Q)
- Vitamins (EX: Vitamins A, D, E, K)
- Light-absorbing pigments (EX: carotene)
What lipid types are covalently linked to other biomolecules?
- Glycolipids
2. Lipoproteins
What are glycolipids and where are they found?
Glycolipids - lipids covalently attached to sugar molecules.
They are found in cell membranes.
EX: ABO blood groups.
What are lipoproteins?
Lipoproteins - lipids covalently attached to proteins.
EX: VLDL, LDL, HDL
What are fatty acids?
Fatty acids (FA’s) - carboxylic acids with hydrocarbon chains 4-36 carbons long.
What types of fatty acids exist?
- Saturated FA’s
- Unsaturated FA’s
- Polyunsaturates FA’s
What are saturated FA’s?
Saturated FA’s - FA’s with no double bonds between carbon links.
What are unsaturated FA’s?
Unsaturated FA’s - FA’s with 1 double bond between carbon links.
What are polyunsaturated FA’s (PUFA)?
PUFA - FA’s with 2+ double bonds between carbon links.
How do we label/number FA’s?
C#1 is assigned to carboxyl carbon; and α (alpha) to the adjacent carbon.
How do we name FA’s using simplified nomenclature?
- Identify number of carbon atoms in the chain
- Identify number and position (if applicable) of double bonds relative to C#1
FORMULA: # of carbons : # of DB (Δ^DB POS.)
EX: 12:0 = 12 C, 0 DB
EX: 18:2 (Δ^9,12) = 18 C, 2, DB @ C9 & C12
How do we name PUFA using alternative nomenclature?
- Identify number of carbon atoms in the chain
- Identify number and position of double bonds relative to C#1
- Identify relative position of DB’s to methyl carbon (last C in chain)
Features of commonly-occurring fatty acids include:
- Even # of C-atoms
- Unbranched
- Cis-oriented DB’s
What are cis-DB’s?
Cis DB’s - functional group is found on the same side across a double bond: kink is introduced in the chain.
What is the bridging pattern of PUFA’s?
Methylene-bridged: DB’s separated by a methylene C.
BOND PATTERN: D - S - S - D
What are trans-FA’s and where are they found?
Trans-FA’s - functional group is found on the opposite side across a double bond: kink is not introduced in the chain.
Occurs due to hydrogenation.
What is hydrogenation?
Hydrogenation - process where unsaturated FA’s get hydrogens added: increases their saturation and allowed extended conformation.
What determined the solubility and MP of FA’s?.
- Chain length (if chain length ↑: solubility ↓, MP ↑)
2. Degree of unsaturation (if unsaturation ↑: solubility ↑, MP ↓)
What effect does saturation have on FA packing?
Saturated FA’s - pack more regularly, straight chains allow fo more favourable interactions between neighbouring ones (VDW forces).
Unsaturated FA’s - pack less regularly, kink in chains yells fewer favourable interactions between neighbouring ones (VDW forces).
What type of acid is phosphoric acid?
Phosphoric acid (H3PO4) - a triprotic acid.
Dissociative nature of phosphoric acid & its derivatives.
At pH 7: exists as equilibrium mixture of H2PO4^(-) & HPO4^(2-); 2nd proton is half-dissociated (denoted by pi).
What are the 2 phosphoric acid reactions?
- Phosphoric acid + alcohol = phosphate ester
2. Phosphoric acid + carboxylic acid = phosphoanhydride
