Many types of cancer cells have been detected to secrete significant levels of lactate. Do you think these cells are likely undergoing beta-oxidation?

Question

A.  Yes, because beta-oxidation can generate intermediates that would lead to the production of lactate.
B.  No, because if lactate is being produced, the cell is not likely making use of the pathways needed to make use of the products of beta-oxidation.
C.  Yes, because lactate stimulates beta-oxidation.
D.  No, because lactate is consumed in beta-oxidation

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 lactate fermentation? How do products from this process indicate how cancer cells derive energy? What other information is related to the question?
   Choose Answer
  Do you have all necessary information to determine which products would affect cellular respiration?
  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

B.  No, because if lactate is being produced, the cell is not likely making use of the pathways needed to make use of the products of beta-oxidation.

Clarify Question
What is the key concept addressed by the question?
        · The question asks you to decide whether or not cancer cells that secrete lactate are undergoing beta-oxidation.
What type of thinking is required?
        · You are being asked to dissect, or analyze, the likelihood that cancer cells that secrete lactic acid are undergoing beta-oxidation.

  Gather Content
  What do you already know about lactate fermentation? How do products from this process indicate how cancer cells derive energy? What other information is related to the question?
        · Recall that cellular respiration is a process of oxidizing glucose in order to produce NADH and ultimately the ATP used to power cellular processes. Respiration is comprised of glycolysis, oxidation of 3-carbon into 2-carbon molecules that then are incorporated into the Krebs cycle, and electron transport and oxidative phosphorylation. With the exception of glycolysis, all of these processes are related to aerobic respiration.
        · At the end of glycolysis, cells can choose to use aerobic processes like the Krebs cycle if there is sufficient oxygen available, or they can use anaerobic processes like lactic acid fermentation when there is no oxygen. Cancer cells in particular tend to use anaerobic processes.
        · Recall that molecules other than glucose are metabolized for energy in cells; this includes breakdown of fatty acids and glycerol and, in certain circumstances proteins into amino acids. Each of these molecules plugs into cellular respiration in different places and under different conditions. The process of breaking down fatty acids is called beta-oxidation and involves cutting fatty acid into two carbon fragments (acetyl-CoA) that plug into the Krebs cycle.
   Choose Answer
  Do you have all necessary information to determine which products would affect cellular respiration?
        · The Warburg effect, discovered by Otto Warburg and since confirmed by observations from other scientists, indicates that many cancer cells derive their energy mainly through the glycolytic pathway coupled with lactic acid (lactate) fermentation. If lactate is produced, that suggests these cells are not engaging in aerobic respiration, including the Krebs cycle, and/or the electron transport chain. This is because cancer cells are using fermentation to regenerate NAD+, instead of using the electron transport chain.
        · Since beta-oxidation generates acetyl-CoA, which can only be used in the Krebs cycle, the observation that these cells are generating lactate suggests that they are not undergoing beta-oxidation. Beta-oxidation does not lead to generation of intermediates that can lead to lactate production, nor does lactate stimulate beta oxidation, and lactate is not consumed through the process of beta-oxidation.         · The long story short here is that cancer cells use anaerobic processes to generate lactate, and since beta-oxidation of fatty acids requires oxygen, cancer cells that operate in the absence of oxygen aren’t using beta-oxidation.

  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 cancer cells that secrete higher levels of lactate are likely undergoing beta-oxidation.
        · If you got the correct answer, well done! If you got an incorrect answer, were you able to recall the stages of cellular respiration and which require oxygen? Were you able to correlate higher levels of lactate with anaerobic metabolism? Were you able to infer that the anaerobic conditions needed for lactate metabolism would prevent aerobic processes like beta-oxidation?