In the absence of carbohydrates such as glucose, other biological macromolecules such as lipids and proteins can be catabolized to obtain energy.

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The statement asks whether, when carbohydrates such as glucose are unavailable, other biological macromolecules like lipids and proteins can be catabolized to obtain energy.
First, consider the fundamental energy pathways: carbohydrates are readily catabolized via glycolysis and the citric acid cycle, but when glucose is scarce, cells can switch to alternative substrates.
Lipids (fats) are broken down into fatty acids and glycerol; fatty acids undergo beta-oxidation to acetyl-CoA, which feeds into the Krebs cycle to produce ATP. This provides a major energy source, especially during fasting or prolonged exercise.
Proteins, when mobilized, are degraded into amino acids; some amino acids can be converted into intermediates that enter the Krebs cycle or gluconeogenesis, supplying energy or enabling glucose production. Although this is not the primary pathway for energy, it can occur under metabolic stress or starvation.
Therefore, the claim that lipids and proteins can be catabolized to obtain energy in the absence of glucose is true. The statement correctly reflects the metabolic flexibility of organisms to utilize alternative macromolecules for energy.
A common misconception would be to think energy extraction is exclusively from carbohydrates; however, the body has mechanisms to oxidize fats and certain amino acids to support ATP production when glucose is limited. This is consistent with the broader understanding of catabolic pathways and energy homeostasis.
Another potential pitfall is to think that proteins are only used for structure or enzymes; while that is true under normal conditions, proteolysis and amino acid catabolism do contribute to energy production when needed, albeit with amino acid deamination and entry into the Krebs cycle or gluconeogenesis.
In summary, in the absence of glucose, lipids and, to a lesser extent, proteins can be catabolized to yield energy, making the statement true.

BIOL_1105_60452_202506 Lesson 09 Homework

In the absence of carbohydrates such as glucose, other biological macromolecules such as lipids and proteins can be catabolized to obtain energy.

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