Problem 91 - Chemistry: The Central Science in SI Units, Global Edition

Question

(a) A serving of a particular ready-to-serve brown \& wild rice meal contains \(4.5 \mathrm{~g}\) fat, \(42 \mathrm{~g}\) carbohydrate, and \(4.0 \mathrm{~g}\) protein. Estimate the number of calories in a serving. (b) According to its nutrition label, the same meal also contains \(140 \mathrm{mg}\) of potassium ions. Do you think the potassium contributes to the caloric content of the food?

Step-by-Step Solution

Answer

(a) The total number of calories in a serving of this meal is approximately 224.5 calories. (b) Potassium does not provide any calories; hence, it does not contribute to the caloric content of the food.

Step 1: Calculate calories from fat, carbohydrate, and protein

Using the given amounts of each nutrient, we will calculate the number of calories contributed by each. (a) Calories from fat: The meal contains 4.5 g of fat, and 1 g of fat provides 9 calories. Therefore, \(calories_{fat} = 4.5g \times 9 \frac{cal}{g} = 40.5 cal\). Calories from carbohydrates: The meal contains 42 g of carbohydrate, and 1 g of carbohydrate provides 4 calories. Therefore, \(calories_{carbohydrate} = 42g \times 4 \frac{cal}{g} = 168 cal\). Calories from protein: The meal contains 4.0 g of protein, and 1 g of protein provides 4 calories. Therefore, \(calories_{protein} = 4g \times 4 \frac{cal}{g} = 16 cal\). Now let's add up the calories from each nutrient to find the total number of calories in a serving of the meal.

Step 2: Calculate the total number of calories in the meal

To calculate the total number of calories, we will add the calories obtained from fat, carbohydrate, and protein nutrients: Total calories = Calories from fat + Calories from carbohydrates + Calories from protein Total calories = 40.5 cal + 168 cal + 16 cal = 224.5 cal So, the total number of calories in a serving of this meal is approximately 224.5 calories. (b) Do you think the potassium contributes to the caloric content of the food? Potassium is a micronutrient, and it does not provide any calories. Hence, the potassium content in the meal does not contribute to the caloric content of the food.

Key Concepts

Caloric Content

Caloric content refers to the number of calories present in a serving of food. Calories are a measure of energy; they indicate how much energy your body can obtain by consuming a specific food. In the context of nutritional chemistry, the primary sources of calories in our diet are macronutrients: fats, carbohydrates, and proteins.

• Fats: Each gram provides 9 calories. In the given exercise, the serving of rice contains 4.5 grams of fat, which equates to 40.5 calories.
• Carbohydrates: Providing 4 calories per gram, 42 grams of carbohydrate in the rice give 168 calories.
• Proteins: Also supplying 4 calories per gram, 4 grams of protein add 16 calories to the meal's total.

Adding these up, the meal's total caloric content is approximately 224.5 calories. This calculation helps individuals understand how much energy they will gain from consuming the food.

Macronutrients

Macronutrients are essential dietary components that supply the bulk of our energy needs. They include fats, carbohydrates, and proteins, each serving a unique role in body functioning and overall nutrition.

• Fats: Fats are dense sources of energy providing 9 calories per gram. They are essential for absorbing vitamins, protecting organs, and maintaining cell membranes.
• Carbohydrates: These are often the body's main energy source, particularly for brain function and during high-intensity exercise. Each gram of carbohydrate provides 4 calories.
• Proteins: Proteins are crucial for building and repairing tissues, making enzymes and hormones. They also provide 4 calories per gram.

Understanding macronutrients is fundamental when assessing the energy contribution of a meal. They not only provide calories but support varied bodily functions, which explains their crucial role in balanced nutrition.

Micronutrients

Micronutrients, unlike macronutrients, do not provide calories and therefore do not contribute to the caloric content of food. However, they are vital for maintaining health and supporting numerous bodily functions. Micronutrients include vitamins and minerals, such as potassium, iron, and vitamin C.

• Potassium: Found in the rice serving from our exercise, potassium is a mineral that aids in nerve function, muscle contraction, and maintaining normal blood pressure.
• Non-caloric Contribution: Despite not providing energy, micronutrients are essential for proper growth, development, and disease prevention.

Micronutrients are essential to a balanced diet. They support life processes and improve overall well-being, even though they do not factor into calorie count directly.