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 metabolizes mainly protein, while Griselda metabolizes mostly carbohydrates and some protein.

Step-by-step solution

Define Catabolic Activities

Catabolism is the process by which the body breaks down food to extract energy. It includes the digestion of proteins, carbohydrates, and fats into simpler molecules.

Analyze Lucullus's Diet

Lucullus only eats canned tuna, which is essentially all protein. This means that his catabolic activity will primarily involve breaking down proteins into amino acids.

Analyze Griselda's Diet

Griselda eats dry cat food that is 70% carbohydrate and 30% protein. Thus, her catabolic activity includes the breakdown of carbohydrates into glucose and proteins into amino acids.

Compare Catabolic Activity of Lucullus and Griselda

Lucullus's catabolic process will predominantly focus on extracting energy from proteins. Griselda's catabolic process will involve both carbohydrate and protein breakdown, with a larger proportion of energy derived from carbohydrates.

Conclude the Differences and Similarities

Both cats break down proteins as part of their catabolism, so this activity is a similarity. However, the key difference is that Lucullus only breaks down proteins, whereas Griselda predominantly breaks down carbohydrates with some protein metabolism.

Key concepts

Catabolic Process

Catabolism is a fundamental biological process in which cells break down complex molecules, like proteins, carbohydrates, and fats, into simpler ones to release energy. This energy is vital for various cellular functions, including growth and repair.
During catabolism, proteins are broken down into amino acids, carbohydrates into glucose, and fats into fatty acids and glycerol. These simpler molecules can then be utilized by the body for energy or further processing. Key features of catabolic activities include:

• Energy release: Through the breakdown of molecules, energy is released and stored in the form of ATP (adenosine triphosphate).
• Molecular breakdown: Large complex molecules are broken into smaller, more manageable ones.
• Waste products: Processes produce waste products that need to be excreted.

Protein Metabolism

Protein metabolism involves breaking down dietary proteins into amino acids, which the body can then utilize. This process occurs primarily in the stomach and small intestine, where enzymes like pepsin and trypsin break down protein chains.
For a cat like Lucullus, who consumes mostly protein (canned tuna), the catabolic activity will heavily focus on protein metabolism. The breakdown process includes:

• Proteolysis: Proteins are degraded into amino acids by enzymes.
• Amino acid absorption: Once broken down, amino acids are absorbed into the bloodstream.
• Liver processing: The liver further processes amino acids, which can be used for energy or converted into other compounds.

Since Griselda also consumes some protein (30% of dry food), her body undergoes similar protein metabolism, but it is balanced with carbohydrate metabolism.

Carbohydrate Metabolism

Carbohydrate metabolism involves the breakdown of carbohydrates into glucose, which is a primary energy source for cells. This process starts in the mouth with enzymes like amylase and continues in the small intestine.
Since Griselda's diet consists of 70% carbohydrates, a significant portion of her catabolic activities is focused on carbohydrate metabolism.

• Digestion: Carbohydrates are broken down into simpler sugars like glucose.
• Absorption: Glucose is absorbed into the blood and transported to cells.
• Glycolysis: Inside cells, glucose is broken down further to produce ATP, the energy currency of the cell.

In contrast, Lucullus, who eats mostly protein, will have minimal carbohydrate metabolism, relying primarily on proteins for energy.

Energy Extraction

Energy extraction from food is crucial for survival and involves obtaining ATP through catabolic processes. Both cats extract energy through different metabolic pathways based on their diet.
For Lucullus, whose diet is protein-rich, energy extraction involves primarily breaking down amino acids which can then enter the Citric Acid Cycle to generate ATP.

• Amino acids metabolism: Amino acids are deaminated, and their carbon skeletons are used to produce energy.
• ATP Generation: This process is less efficient compared to glycolysis from carbohydrates.

Griselda, on the other hand, extracts energy mainly from carbohydrates, which provide a more efficient and rapid ATP generation through glycolysis and the Citric Acid Cycle.

Diet Analysis

Analyzing the diets of Lucullus and Griselda provides insights into their differing metabolic processes.
Lucullus’s diet, being high in protein, necessitates an efficient protein metabolism system. This can be observed from his high dependence on amino acid breakdown for energy.

• High protein intake: Leads to increased amino acid catabolism.
• Protein-focused metabolism: Prioritizes breakdown of complex protein molecules.

Griselda’s diet, with a 70% carbohydrate composition, implies that her metabolism is geared towards efficient carbohydrate breakdown.

• High carbohydrate intake: Leads to enhanced glycolysis and glucose oxidation.
• Balanced diet: Involves both carbohydrate and protein metabolism.

This dietary analysis highlights how specific food sources can influence the catabolic processes and overall energy metabolism in cats.