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Questions and Answers
What structure do phospholipids form when added to water?
What components create the hydrophobic nature of phospholipids?
Which type of lipid is characterized by a carbon skeleton consisting of four fused rings?
What role does cholesterol play in animal cell membranes?
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What is one potential health risk associated with high cholesterol levels in the blood?
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Which of the following is NOT one of the three main types of biologically important lipids?
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What part of the phospholipid molecule is hydrophilic?
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What is the function of phospholipids in the cell membrane?
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What is the primary characteristic that unifies lipids?
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Which of the following statements is true regarding fats?
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What distinguishes saturated fatty acids from unsaturated fatty acids?
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What components make up a fatty acid?
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What effect does the presence of a cis double bond have on unsaturated fatty acids?
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Which of the following is NOT one of the three main types of biologically important lipids?
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What is the role of the hydroxyl group in glycerol?
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What type of bond characterizes unsaturated fatty acids?
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What are the components joined by ester linkage to form a triacylglycerol?
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Which type of fat is typically solid at room temperature?
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What is the main function of fats in the body?
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What process converts unsaturated fats to saturated fats?
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Why do fats separate from water?
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Which type of fatty acids contribute to cardiovascular disease through plaque deposits?
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What characterizes phospholipids as amphipathic molecules?
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What type of molecules make up the majority of biologically important lipids?
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Study Notes
Lipids
- Lipids are a diverse group of hydrophobic molecules.
- The unifying feature of lipids is their hydrophobic nature—they mix poorly with water.
- Lipids consist mostly of hydrocarbon regions, which are nonpolar.
- Like dissolves like, so nonpolar lipids do not readily dissolve in polar water.
- There are three main types of lipids: fats, phospholipids, and steroids.
Fats
- Fats are constructed from glycerol and fatty acids.
- Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon.
- A fatty acid consists of a long hydrocarbon skeleton with a carboxyl group at one end.
- Fatty acids vary in length and in the number and locations of double bonds.
- Saturated fatty acids have the maximum number of hydrogen atoms and no double bonds.
- Unsaturated fatty acids have one or more double bonds.
- In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride.
- The fatty acids in a fat can be the same or different.
Saturated and Unsaturated Fats
- Saturated fats are solid at room temperature and are typically found in animal products.
- Unsaturated fats are liquid at room temperature and are usually found in plants and fish.
- A diet rich in saturated fats may contribute to cardiovascular disease.
Hydrogenation
- Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen.
- This process creates trans fats, which are unhealthy and may contribute more to cardiovascular disease than saturated fats.
Function of Fats
- The primary function of fats is energy storage.
- Humans and other mammals store their long-term food reserves in adipose cells.
- Adipose tissue also cushions vital organs and insulates the body.
Phospholipids
- Phospholipids have two fatty acids and a phosphate group attached to glycerol.
- Phospholipids are amphipathic molecules.
- The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head.
- When phospholipids are added to water, they self-assemble into double-layered sheets called bilayers, with the hydrophobic tails pointing toward the interior and the hydrophilic heads facing the water. The bilayers form a boundary between the cell and its external environment.
Steroids
- Steroids are lipids characterized by a carbon skeleton consisting of four fused rings.
- Cholesterol is a type of steroid that is a component in animal cell membranes and a precursor for other steroids.
- A high level of cholesterol in the blood can contribute to cardiovascular disease.
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Description
This quiz covers the essential characteristics of lipids, including their hydrophobic nature and classification into fats, phospholipids, and steroids. You'll learn about the structure of fats, including glycerol and fatty acids, and the differences between saturated and unsaturated fatty acids. Test your knowledge on the basics of lipids and their functions in biological systems.
