In order to lose weight and reduce body fat, a friend of yours has decided to eliminate all fat from his diet, while consuming unrestricted amounts of carbohydrates. What do you think of this idea?

Question

A.  It is a good idea, because if your friend doesn't eat any fat, he cannot store any additional fat.
B.  It is a bad idea, because consumption of fat is required to provide cofactors for the electron transport chain.
C.  It is a good idea, because under conditions where ATP levels are low in cells, carbohydrates will be stored, and fat stores will be catabolized via beta-oxidation to generate energy.
D.  It is a bad idea, because if ATP levels are high in cells, excess acetyl-CoA from the metabolism of carbohydrates can be used for fatty acid synthesis.

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

  Gather Content
  What do you already know about consuming carbohydrates and weight loss? Is excessive carbohydrate intake a good or bad idea? What other information is related to the question?

  Choose Answer
  Do you have all the information needed to determine whether or not excessive consumption of carbohydrates will help or harm your friend?

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

D.  It is a bad idea, because if ATP levels are high in cells, excess acetyl-CoA from the metabolism of carbohydrates can be used for fatty acid synthesis.

Clarify Question
What is the key concept addressed by the question?
        · The question asks you to determine whether or not it is a good idea for your friend to only consume carbohydrates in an attempt to lose weight.
What type of thinking is required?
        · You are being asked to analyze the feasibility of your friend losing weight by only consuming carbohydrates.

  Gather Content
  What do you already know about consuming carbohydrates and weight loss? Is excessive carbohydrate intake a good or bad idea? What other information is related to the question?
        · You hear in the news all the time that we consume too many carbohydrates in our diets. Why the big concern? What harm could it be? Since we know that our bodies metabolize organic fuels through cellular respiration, let’s use what we already know about how cellular respiration works.
        · Organic fuels are broken down via cellular respiration, including glycolysis, pyruvate oxidation, the Krebs cycle, and electron transport. These are catabolic processes that convert bonds in organic molecules into energy stored in ATP that cells use to do work. But what happens when we have all the energy our cells need? What do we do with the excess molecules?

  Choose Answer
  Do you have all the information needed to determine whether or not excessive consumption of carbohydrates will help or harm your friend?
        · The metabolism in our cells is a finely-tuned balance of catabolic and anabolic processes. We use catabolic processes to break down organic molecules and harness their energy via cellular respiration. However, when our cells have all the energy (ATP) they need, they tend to save the excess organic molecules for a rainy day, so to speak. This allows the cell to store reserve energy for when the cell needs organic molecules but none are available.
        · If your friend consumes nothing but carbohydrates, ATP levels will be high and anabolic processes will engage. This will prompt excess acetyl-CoA to be converted into fatty acids, which is converted into fat. So, consuming nothing but carbohydrates is bad because there is no way for your cells to use it all and it will eventually get stored as fat.

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · Answering this question correctly depended on your ability to analyze whether or not your friend could lose weight by consuming nothing but carbohydrates.
        · If you got the correct answer, well done! If you got an incorrect answer, were you aware that metabolism is a balance of catabolic and anabolic processes that sense cellular ATP levels? Were you able to infer that excess carbohydrate would lead to high ATP levels, prompting the extra acetyl-CoA to be converted into fatty acids? Were you able to draw the conclusion that eating only carbohydrate is a bad idea?