lipids Flashcards
functions of lipids
Storage of energy: reduced compounds (lots of available energy) and hydrophobic nature (good packing)
Insulation from environment: low thermal conductivity, high heat capacity, mechanical protection (absorb shock)
Water repellant: hydrophobic nature keeps organism dry
Membrane structure
Cofactors for enzymes
Signaling molecules
Pigments
Antioxidants
What are fatty acids?
carboxylic acids with hydrocarbon chains containing 4-30 carbons (almost all have even number of carbons).
saturated: has no double bonds
monounsaturated: has one double bond
polyunsaturated: has more than one double bond
What effects lipid solubility and melting point?
solubility: larger chain = lower solubility. it’s hard to know how unsaturations will impact solubility
melting point: decreases as the chain length decreases, less bonds to break. also decreases as number of double bonds increases due to the unfavorable interactions from the kinking. the unfavorable packing takes less energy to disrupt
how are trans fatty acids formed and what does this change about melting point?
partial hydrogenation of unsaturated fatty acids. they support an extended conformation with closer packing and high melting points
what are triacylglycerols?
the majority of fatty acids in biological systems are triacylglycerols with three fatty acids connected. Solids are called fats and liquid are called oils.
They are the primary storage form of lipids and are less soluble in water and less dense than water
what makes fats good fuel storage compared to polysaccharides?
fatty acids carry more energy per carbon because they are more reduced (no alcohol group)
fatty acids carry less water per gram because they are non polar.
This means that Fats are good for long term energy and glucose/gycogen are for short term
what are glycerophospholipids?
two fatty acids form ester linkages with the hydroxyl groups of L-glycerol-3-phosphate. There is also often a polar head group attached to the phosphate group (this defines which phospholipid it is). These are the primary constituents of cell membranes
phosphatidylcholine
major component of most eukaryotic cell membranes. most prokaryotes cannot synthesize this lipid
plasmalogen
an ether lipid similar to phosphatidylethanolamine. Common in vertebrate heart tissue, function not well understood. It would resist some cleavages due to the ether linkage
platelets-activating factor
aliphatic ether analog of phosphatidylcholine. Has an acetyl ester at C2 and an ether linked alkane at C3.
Signaling lipid, stimulates aggregation of blood platelets, plays role in mediation of inflammation
sphingolipids
has sphingosine backbone instead of glycerol backbone. fatty acid is joined to sphingosine via amide linkage. A polar head group is connected by glycosidic or phosphodiester linkage.
sphingomyelin
sphingolipid with phosphocholine attached to the alcohol. Abundant in myelin sheath that surrounds nerve cells
How do glycosphingolipids affect blood groups?
blood groups are determined in part by the type of sugars on the head group of glycosphingolipids.
No active glucosyltransferase is O blood
Glucosyltransferase with N-acetylgalactosamine group is A blood
Glucosyltransferase with galactose group is B blood
What is lipase and phospholipase?
lipase is the enzyme that hydrolyzes lipids at the ester carbonyls. it will act on all the fatty acids present
phospholipase hydrolyzes at specific fatty acids. (A1 at C1, A2 at C2, C at P-O bond, and D at head group link)
what is the structure and function of sterol?
four fused rings (sterol nucleus) with a hydroxyl head group (polar) and various non polar side chains.
main one is cholesterol: present in cell membranes and modulates fluidity and permeability, also thickens membrane. transported via blood to tissues
many other sterols are hormones
