Intro to Lipids and Their Metabolism - RM Flashcards
What are the complexities of lipids and their metabolism related to?
their heterogeneity and water insolubility
What is the major storage form of metabolic energy in humans? What is its structure?
triacylglycerides (TG), 3 C backbone of glycerol with the 3 OH groups esterified to fatty acid chains
How does length of R group affect the solubility of triglycerides?
short R groups, more soluble due to polarity of carboxyl groups
long R groups, more hydrophobic, less soluble
What is the 4 step overview of TG metabolism in intestine?
- digestion of TG into 2-MAG and fatty acids
- absorption of components into intestinal cells
- resynthesis of TG by intestinal cells
- assembly of TG into lipoproteins for export to lymph to blood
What are the 3 reasons to store metabolic energy as fat?
- carbons in TG have lower oxidation state (more highly reduced, has 2x as much energy per dry weight)
- stored in anhydrous state (carbs have bound water that adds to weight)
- don’t participate in osmotic balance (can be stored to large fraction of cell volume)
What is the structure of a fatty acid?
carboxylic acid with an alkyl side chain, normally chains of 16 or 18 carbons
What type of polyunsaturated hydrocarbon chains can a fatty acid not have?
ones with adjacent double bonds or conjugated double bonds because it would be too easily oxidizable
(usually separated by a methylene group)
What type of double bonds are found naturally occuring? Why?
cis, interferes with packing, lower Tm, keeps the membrane fluid
How are LCFAs kept from being toxic to cell (free, ionized LCFA)?
esterified or tightly bound to FA-binding proteins intracellularly or albumin extracellularly
Why do fatty acids have even numbers of carbons?
synthesized 2 carbons at a time
What cannot use fatty acids as fuel and why can’t it?
brain, free fatty acids can’t cross blood brain barrier
How are fatty acids used for fuel?
FA-derived acetyl coA enters citric acid cycle to give ATP and heat
What are the sources of non-esterified fatty acids (NEFA)?
dietary fat (TG) and fatty acids synthesized de novo by liver and adipocytes
How many carbons and double bonds in myristic acid?
14 C, 0 double bonds
How many carbons and double bonds in palmitic acid?
16 C, 0 double bonds
How many carbons and double bonds in palimtoleic acid?
16 C, 1 double bond
How many carbons and double bonds in stearic acid?
18 C, 0 double bonds
How many carbons and double bonds in oleic acid?
18 C, 1 double bond