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Questions and Answers
What forms the major driving force for the formation of lipid bilayers?
What forms the major driving force for the formation of lipid bilayers?
Phospholipids contain an alcohol, two fatty acids, and a phosphate ester.
Phospholipids contain an alcohol, two fatty acids, and a phosphate ester.
True
What are glycerophospholipids also known as?
What are glycerophospholipids also known as?
Phosphoglycerides
Lecithin is a glycerophospholipid in which the additional phosphate ester is attached with __________.
Lecithin is a glycerophospholipid in which the additional phosphate ester is attached with __________.
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What is the role of phosphatidylinositol 4,5-bisphosphates (PIP2)?
What is the role of phosphatidylinositol 4,5-bisphosphates (PIP2)?
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Sphingosine is a long-chain amino alcohol found in sphingolipids.
Sphingosine is a long-chain amino alcohol found in sphingolipids.
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Which carbohydrate is primarily found in cerebrosides?
Which carbohydrate is primarily found in cerebrosides?
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What is the most abundant steroid in the human body?
What is the most abundant steroid in the human body?
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Steroids contain a core structure called the __________ nucleus.
Steroids contain a core structure called the __________ nucleus.
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Study Notes
Complex Lipids
- Complex lipids form biological membranes
- They spontaneously form lipid bilayers in aqueous solutions
- Hydrophilic head groups face the aqueous environment
- Hydrophobic tails are buried within the bilayer
- Hydrophobic interactions drive the formation of bilayers
- The arrangement of tails can be rigid (saturated) or fluid (unsaturated)
Phospholipids
- Similar to triacylglycerol but replace one fatty acid with a phosphate group and an amino alcohol
- Contains an alcohol, two fatty acids, and a phosphate ester
- Can be degraded by phospholipases
Glycerophospholipids
- Also known as phosphoglycerides
- The second most abundant lipids in the body
- Component of cell membranes
- Similar structure to fats but with glycerol as the alcohol
- Two hydroxyl groups esterified with fatty acids
- Third hydroxyl group esterified with phosphoric acid, which is also bonded to another alcohol
- Most common are derived from phosphatidic acid, which has glycerol esterified with two fatty acids and one phosphate
- Fatty acid on carbon 2 of glycerol is always unsaturated
- Further esterification with an alcohol (e.g. choline or ethanolamine) forms a glycerophospholipid
Glycerophospholipids: Lecithin
- Glycerophospholipid with choline attached to phosphate ester
- Major component of egg yolk
- Excellent emulsifier due to its polar and nonpolar components
Glycerophospholipids: Cephalins
- Glycerophospholipids with ethanolamine or serine attached to a phosphate ester
- Found in cell membranes
Glycerophospholipids: Phosphatidylinositols (PI)
- Inositol is bonded to phosphate group
- Phosphorylated forms, such as PIP2, act as signaling molecules in cell communication
Sphingolipids
- Contain sphingosine, a long-chain amino alcohol
- Myelin, a sphingolipid, is found in the coatings of nerve axons
- Ceramide part can incorporate various fatty acids like stearic acid
- Found in cerebrosides
Glycolipids
- Complex lipids containing carbohydrates and ceramides
- Carbohydrate is usually glucose or galactose
- Cerebrosides are ceramides with mono- or oligosaccharides, found in the brain and nerve synapses
- Gangliosides have more complex carbohydrates
Derived Lipids: Steroids
- Contain a steroid nucleus, a tetracyclic ring structure with three cyclohexane rings and one cyclopentane ring
- Differ in functionality due to substituent groups attached to the core structure
- Rings are designated A, B, C, and D
- Carbons are numbered starting from ring A and ending at methyl groups
Cholesterol
- Most abundant steroid in humans
- Component of cell membranes
- Precursor for other steroid hormones like bile salts, vitamin D, and sex hormones
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