In this weeks forum article Nutrient Utilization in Humans M

In this week’s forum article, Nutrient Utilization in Humans: Metabolism Pathways,(http://www.nature.com/scitable/topicpage/nutrient-utilization-in-humans-metabolism-pathways-14234029) the types of molecules and the mechanisms by which the potential chemical energy in those molecules is transformed into the type of energy capable of powering cellular work is discussed. After reading the article, answer the questions listed below. ( Read the article and answer the following questions)

1. What was Antoine Lavoisier’s major contribution to our understanding of energy metabolism in living organisms?

2. Max Rubner showed that carbohydrates and proteins produce approximately 4 Kcal/g of energy when oxidized, whereas lipids generate up to 9 Kcal/g. How can this difference be explained?

3. This article points out that a major misconception, especially for many undergraduates, is that human cells only use glucose as a fuel source. In fact, all three major absorbed end products of the digestion of carbohydrates, lipids and proteins can be utilized by most cells for the generation of ATP. What serves as the major entry point (mechanism) for these different classes of molecules that makes it possible for them to serve as fuel for ATP production? Why does this mechanism not work in the absence of oxygen?  Hint: consider glycolysis and fermentation.

4. Although many of the approximately 200 cell types in the human body can utilize all three major classes of food molecules for energy, not all can. Why? Provide an example.

Solution

1: Antoine Lavoisier is credited with discovery that the living things generate heat which in turn led to the concept of metabolis in living things.
2: The stored forms of lipids are fats and oils which are fatty acid derivatives. The fatty acids are the highly reduced hydrocarbon derivatives that produces huge amount of energy under controlled rapid oxidation. Proteins and carbohydrates have higher oxidation states as compared to lipids and therefore produce lesser amount of energy.