Final answer:
Triglycerides, a type of lipid, are a better storage form of metabolic fuels than polysaccharides like glycogen or starch due to their higher energy density, lower water retention, and ability for long-term storage.
Step-by-step explanation:
Triglycerides, which are a type of lipid like triacylglycerols, are a better storage form of metabolic fuels than polysaccharides like glycogen or starch due to several reasons:
- Energy density: Triglycerides store about twice as much energy as carbohydrates. This is because lipids contain more carbon-carbon bonds and fewer oxygen atoms compared to carbohydrates, resulting in a higher energy yield upon their oxidation.
- Water retention: The presence of fewer oxygen atoms in lipids compared to carbohydrates leads to a lower water content. This is advantageous for storage purposes as water molecules are heavy and can add unnecessary weight.
- Long-term storage: Lipids are primarily stored in the adipose tissue and can provide a long-lasting source of energy. They can be broken down through beta-oxidation, converting their fatty acid chains into acetyl groups that enter the citric acid cycle and generate ATP.