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Ch.3 Matter and Energy
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 3, Problem 31d

Using the energy values for foods (see TABLE 3.7), determine each of the following (round off the answer for each food type to the tens place):
d. the grams of fat in one avocado that has 405 kcal, 13 g of carbohydrate, and 5 g of protein

Verified step by step guidance
1
Step 1: Recall the energy values for macronutrients. From Table 3.7, the energy values are: carbohydrates = 4 kcal/g, proteins = 4 kcal/g, and fats = 9 kcal/g.
Step 2: Calculate the total energy contribution from carbohydrates. Multiply the grams of carbohydrate (13 g) by the energy value for carbohydrates (4 kcal/g): E=13×4.
Step 3: Calculate the total energy contribution from protein. Multiply the grams of protein (5 g) by the energy value for proteins (4 kcal/g): E=5×4.
Step 4: Subtract the energy contributions from carbohydrates and protein from the total energy (405 kcal) to find the energy contribution from fat: E=405-(Energy_carbohydrates+Energy_protein).
Step 5: Determine the grams of fat by dividing the energy contribution from fat by the energy value for fats (9 kcal/g): grams=Energy_fat÷9.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Caloric Value of Macronutrients

Each macronutrient contributes a specific number of calories per gram: carbohydrates provide 4 kcal/g, proteins also provide 4 kcal/g, and fats provide 9 kcal/g. Understanding these values is essential for calculating the total caloric content of a food item based on its macronutrient composition.
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Energy Balance Equation

The energy balance equation states that the total energy intake from food must equal the total energy expenditure for weight maintenance. In this context, knowing the total caloric content of the avocado allows for the calculation of the grams of fat by subtracting the calories contributed by carbohydrates and proteins from the total calories.
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Nutritional Calculation

Nutritional calculation involves using known values of macronutrients to determine the composition of a food item. In this case, by applying the caloric values of carbohydrates and proteins to the total caloric content of the avocado, one can isolate the calories from fat and subsequently convert that into grams of fat.
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