How are fats, phospholipids, and steroids alike? A. They are all solid at room temperature. B. They each contain a polar phosphate group. C. They each contain only 1 fatty acid. D. They do not dissolve in water. E. They all contain at least one carbon ring.
The correct answer and explanation is:
The correct answer is D. They do not dissolve in water.
Explanation:
Fats, phospholipids, and steroids are all types of lipids, which share common characteristics, particularly in their behavior in water. Here’s a breakdown of their similarities:
- Hydrophobic Nature (Do Not Dissolve in Water): All lipids, including fats, phospholipids, and steroids, are hydrophobic or non-polar, meaning they do not dissolve in water. This is because the structure of these molecules includes long hydrocarbon chains or rings that are not attracted to water molecules. Instead, these lipids tend to aggregate together to avoid water, which is a feature that unites them.
- Fats (Triglycerides): Fats, also known as triglycerides, are composed of three fatty acid chains attached to a glycerol molecule. These fatty acids are long chains of carbon and hydrogen atoms, which makes them hydrophobic. Fats are used primarily for energy storage, insulation, and protection of organs. At room temperature, some fats are solid (like butter) due to their saturated fatty acid content, while others are liquid (like oils).
- Phospholipids: Phospholipids are similar to fats in that they have long fatty acid chains, but they also have a phosphate group attached to the glycerol backbone. The presence of the polar phosphate group makes part of the molecule hydrophilic (water-attracting), while the fatty acid tails are hydrophobic. This amphipathic nature is crucial for forming the bilayer structure of cell membranes, where the hydrophobic tails face inward, away from water, and the hydrophilic heads face outward, toward water.
- Steroids: Steroids, such as cholesterol and hormones like testosterone, have a completely different structure. They consist of four interconnected carbon rings, but they are still hydrophobic. While they do not have the long chains of fatty acids found in fats and phospholipids, their overall non-polar character makes them insoluble in water as well.
In summary, fats, phospholipids, and steroids are similar because they all exhibit hydrophobic behavior and do not dissolve in water. This is a defining feature of lipids, which distinguishes them from water-soluble molecules.