Questions and Answers
Which of the following best describes lipids?
What characterizes most membrane lipids?
They are amphipathic, having a non-polar end and a polar end.
What is the formula representation for a 16-C fatty acid?
CH3(CH2)14-COO-
What configuration do double bonds in fatty acids usually have?
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Which of the following is a common fatty acid and its name?
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What is the backbone of glycerophospholipids?
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In phosphatidate, fatty acids are esterified to hydroxyls on C1 & C2, and the C3 hydroxyl is esterified to ______.
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What role does phosphatidylinositol play besides being a membrane lipid?
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Which component is a polar head group in glycerophospholipids?
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Study Notes
Lipids Overview
- Lipids are hydrophobic compounds which are soluble in organic solvents.
- Most lipids are amphipathic, featuring both a non-polar and a polar end.
Fatty Acids
- Fatty acids consist of a hydrocarbon chain with a carboxylic acid group at one end.
- Example structure of a 16-carbon fatty acid: CH3(CH2)14-COO-.
- Double bonds in fatty acids typically have a cis configuration, causing a "kink" in the chain.
- Common fatty acids include:
- 14:0 myristic acid
- 16:0 palmitic acid
- 18:0 stearic acid
- 18:1 cisD9 oleic acid
- 18:2 cisD9,12 linoleic acid
- 18:3 cisD9,12,15 α-linolenic acid
- 20:4 cisD5,8,11,14 arachidonic acid
- 20:5 cisD5,8,11,14,17 eicosapentaenoic acid (an omega-3)
Glycerophospholipids
- Glycerophospholipids (phosphoglycerides) are major components of cellular membranes.
- Comprised of a glycerol backbone and two esterified fatty acids on carbon positions 1 and 2, with carbon 3 esterified to phosphate (Pi).
Ester Formation
- Esters form through the reaction of a hydroxyl group with a carboxylic acid, releasing water (H2O).
- General ester formation reaction: R'OH + HO-C-R" → R'-O-C-R'' + H2O.
Structure of Phosphatidate
- In phosphatidate, two fatty acids are attached to a glycerol backbone, and a phosphate group is attached to the third carbon (C3).
Glycerophospholipid Diversity
- Glycerophospholipids often have diverse polar head groups, such as serine, choline, ethanolamine, glycerol, or inositol.
- Variations in fatty acids may occur in length or presence of double bonds, resulting in non-identical tails.
Example Glycerophospholipids
- Phosphatidylinositol serves as both a membrane lipid and plays a role in cell signaling.
- Phosphatidylcholine, with its choline head group, is another common membrane lipid.
Molecular Structure
- Each glycerophospholipid consists of a polar region (glycerol, carbonyl oxygen from fatty acids, phosphate, and polar head group) and non-polar hydrocarbon tails (fatty acids R1, R2).
- The presence of double bonds in fatty acids introduces kinks, affecting membrane fluidity.
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Description
Test your knowledge on lipids and their role in membrane structures. This quiz covers concepts such as amphipathic properties, fatty acid structures, and the significance of double bonds in fatty acids. Perfect for students studying cell biology or biochemistry!
