Question

A cat named Lucullus is so spoiled that he will eat nothing but freshly opened canned tuna. Another cat, Griselda, is given only dry cat food by her far less indulgent owner. Canned tuna is essentially all protein, whereas dry cat food can be considered \(70 \%\) carbohydrate and \(30 \%\) protein. Assuming that these animals have no other sources of food, what can you say about the differences and similarities in their catabolic activities? (The pun is intended.)

Short answer

Lucullus catabolizes only protein, generating more nitrogenous waste. Griselda catabolizes both carbohydrates and proteins, leading to more diverse catabolic activities.

Step-by-step solution

Identify the Nutrients in Each Diet

Lucullus consumes only canned tuna, which is entirely protein. Griselda consumes dry cat food, which is 70% carbohydrate and 30% protein.

Determine the Protein Intake

Lucullus's diet is 100% protein. Griselda’s diet is 30% protein. Thus, Lucullus consumes more protein proportionally than Griselda.

Determine the Carbohydrate Intake

Lucullus's diet contains 0% carbohydrates. Griselda’s diet, which is 70% carbohydrates, means she consumes carbohydrates while Lucullus does not.

Analyze Catabolic Activities

Lucullus's metabolism is focused on breaking down proteins. Griselda’s metabolism breaks down both carbohydrates and proteins.

Compare the Metabolism

Lucullus might generate more nitrogenous waste due to higher protein catabolism. Griselda’s diet includes carbohydrates, meaning her body splits its catabolic activities between carbohydrates and proteins, possibly making her catabolism more diverse.

Evaluate Energetics

Proteins and carbohydrates yield different amounts of energy through catabolism. Since carbohydrates are a more direct source of energy, Griselda might have quicker energy availability compared to Lucullus.

Consider Similarities

Both cats utilize proteins in their diets, indicating that they share similar pathways for protein catabolism.

Key concepts

Protein Catabolism

Protein catabolism refers to the breakdown of proteins into smaller units, such as amino acids, which can then be used for energy, or to synthesize new proteins and other important biomolecules. In Lucullus's case, consuming only canned tuna means his body primarily performs protein catabolism. This process results in the release of nitrogen, which can form nitrogenous waste like urea and ammonia. This is why Lucullus may produce more nitrogenous waste compared to Griselda. Additionally, proteins are converted to energy at a lower efficiency compared to carbohydrates. This means Lucullus’s body has to work harder to get the same amount of energy as Griselda's does.

Protein catabolism can be summarized in these steps:

• Proteins are broken down into amino acids.
• Amino acids are deaminated, removing the amino group.
• The remaining carbon skeletons are then converted into intermediates that can enter the Krebs cycle for energy production.

Despite the complexity, proteins are essential. They not only provide energy but also support growth, repair tissues, and maintain enzymes and hormones essential for bodily functions.

Carbohydrate Metabolism

Carbohydrate metabolism is the way our bodies process carbohydrates to generate energy. For Griselda, who consumes dry cat food with 70% carbohydrates, this is a significant aspect of her catabolism. Unlike proteins that need to be broken down into amino acids, carbohydrates are more straightforward as they typically need to be converted into simpler sugars like glucose. Glucose is a primary energy source for cells.

Here's the basic outline of carbohydrate metabolism:

• Carbohydrates are digested and converted into simple sugars like glucose.
• Glucose enters the bloodstream and is transported to cells.
• In cells, glucose undergoes glycolysis to form pyruvate, producing a small amount of energy in the form of ATP.
• Pyruvate enters the mitochondria to be further broken down in the Krebs cycle, leading to the production of even more ATP.

Carbohydrates offer a more