Lipids Flashcards
What are lipids?
H2O-insoluble molecules that are highly soluble in organic solvents, used to store energy, key components of membranes, many roles in signal-transduction pathways, cannot form polymers
What are the five classes of lipids?
- Free fatty acid (nonesterified fatty acids)
- Triacylglycerols
- Phospholipids
- Glycolipids
- Steroids
What are fatty acids (fats)?
hydrocarbon chains of various lengths (even #s of C-atoms from 14-24), may have more than 1 double bond depending on fat, that terminate with carboxylic acid group.
Free fatty acids in cells or blood are low because they are strong acids = pH imbalance
What is the structure of fatty acids?
Hydrocarbons with a terminal carboxylic group
What are the two key roles of fatty acids?
Fuels and building blocks of membrane lipids
- Good fuels because they are more reduced than carbs (C bonded to H instead of O), which yields more energy than carbs when undergoing combustion to CO2 and H2O
How can the fluidity of fatty acids be enhanced?
Short-chain length and cis unsaturation (controlled by melting point = shorter, more unsat, cis = low mp)
What are triacylglycerols?
The most efficient storage form of fatty acids, formed by the attachment of 3 fatty acid chains to a glycerol molecule, attached by ester linkages.
Located in adipose tissues (adipocytes)
Why are triacylglycerols efficient storage forms?
- More reduced than carbs (less O), so they have more energy per gram (more energy readily available)
- Stored more efficiently due to their hydrophobicity (water is excluded)
What are the three kinds of membrane lipids?
Phospholipids, glycolipids, and cholesterol
What are phospholipids?
Constructed from 4 components: at least 1 fatty acid, platform to which fatty acids are attached, a phosphate, and an alcohol attached to the phosphate
What are phosphoglycerides?
Derived from glycerol, composed of a glycerol backbone, which is attached to two fatty acids and phosphorylated alcohol. C1 and C2 of the glycerol are esterified to carboxyl groups of two fatty acid chains, C3 hydroxyl group is esterified to phosphoric acid.
Phosphatidate is the simplest phosphoglyceride from which
major phosphoglycerides are derived by forming an ester linkage between the phosphoryl group of phosphatidate and hydroxyl group of one of several alcohols
Sphingolipids are
phospholipids that are built on a sphingosine backbone
What are steroids?
Lipids that function as powerful hormones, facilitate digestion of lipids in diet, and are key membrane components. All have tetracyclic ring structure called steroid nucleus.
All biochemically important steroids are modified versions of what basic structure?
Steroid nucleus (3 cyclohexane rings and cyclopentane ring joined together)
