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
What is a terpenoid (isoprenoid)?
A molecule derived from isoprene units
Name 3 important molecules derived from terpenoids.
Vitamin A, Vitamin K, Ubiquinone (CoQ10)
What are lipoproteins?
Complexes of lipids and proteins that transport fats in the bloodstream
What are lipopolysaccharides (LPS)?
Complexes of lipids and carbohydrates found in bacterial outer membranes
What are waxes made of?
Long-chain fatty acids and long-chain alcohols
Where does a fatty acid with omega-6 come from?
Plants
How does the systematic numbering system begin in fatty acids?
Carbon 1 is the carboxylic acid
What is the alternative method to systematic numbering in fatty acids?
Omega to reference carbon other end of carboxyl carbon. Next one in from carboxyl is alpha, then beta, then end one is always omega
What does it mean if something is a phosphosphingolipid?
It contains sphingosine (not glycerol like phospholipids)
Has a phosphate group
And often includes a choline head group (just like phosphatidylcholine
What is the cis form of a biological fatty acid?
Both hydrogens on the same side
What is the primary oxidation in bodied?
Beta oxidation
What is the most common saturated fatty acid?
Palmitic acid
What does trienoic mean?
3 double bonds
What are the 3 essential fatty acids?
Alpha linoleic acid
Linoleic acid
Arachidonic acid - only essential if deficient in linoleic acid
What is a TAG with 3 steroid acid chains called?
Tristearolyglycerol
What is a TAG with 3 oleic acid residues called?
Trioeoylglycerol
What are the 3 components of a sphingosine?
A long hydrocarbon tail (like fatty acids)
A hydroxyl group (-OH)
An amino group (-NH₂)
What are sphingolipids?
A class of lipids that use sphingosine as their backbone instead of glycerol (which is used in phospholipids and triglycerides).
What are terpenoids?
Lipid-based molecules built from repeating units of a simple 5-carbon molecule called isoprene (C₅H₈)
