Lipids Flashcards
What is the general structure of a fatty acid? Which parts are polar and non-polar?
A hydrocarbon tail (nonpolar) with a carboxylic acid group (COOH) at one end (polar)
What determines the melting point of a fatty acid?
Chain length and degree of saturation (more saturation = higher melting point)
What is a saturated fatty acid?
A fatty acid with no double bonds
What is an unsaturated fatty acid?
A fatty acid with one or more double bonds (usually in the cis form)
What is the difference between omega (ω) and systematic fatty acid numbering?
Omega starts from the methyl end; systematic starts from the carboxylic acid end
What does “18:1(n-9)” indicate?
18 carbon atoms, 1 double bond, first double bond 9 carbons from the methyl end
Name two essential fatty acids.
Linoleic acid (omega-6) and alpha-linolenic acid (omega-3)
Why are some fatty acids essential in the human diet?
Humans cannot introduce double bonds beyond the 9th carbon from the carboxyl end
What is the role of arachidonic acid?
It is a precursor to eicosanoids (inflammatory signaling molecules)
CAN REPLACE linoleic acid if deficient
What is a triacylglycerol (TAG)?
A lipid made of 3 fatty acids esterified to a glycerol backbone
Difference between simple and mixed TAGs?
Simple = same fatty acids; Mixed = different fatty acids
Why are fats more efficient for energy storage than carbohydrates?
Fats store ~38 kJ/g, are anhydrous, and take up less space
What is the structure of a phospholipid?
Glycerol + 2 fatty acids + phosphate group with a polar head group
What does amphiphilic mean?
Has both hydrophilic (polar) and hydrophobic (nonpolar) parts
What is the backbone of sphingolipids?
Sphingosine (an amino alcohol)
What is a ceramide?
A sphingosine + fatty acid attached via an amide bond
What is sphingomyelin?
A sphingolipid with phosphorylcholine head group; found in myelin sheath
What are glycolipids?
Lipids with a carbohydrate group instead of phosphate
Where are glycolipids commonly found?
Plant cells and nerve cells
What is the biological role of glycolipids?
Cell recognition and signaling (e.g. blood group antigens)
What defines the structure of a steroid?
4 fused rings (3 six-membered, 1 five-membered)
What is cholesterol?
A steroid important in membranes; amphipathic; precursor to hormones and vitamins
How does cholesterol affect membrane fluidity?
Stabilizes membrane by decreasing fluidity at high temp and increasing at low temp
List 3 steroid hormones derived from cholesterol.
Testosterone, cortisol, aldosterone
