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Human Physiology - Essential Nutrients and Balanced Diet

Grade 9IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Nutrients are chemical substances found in food that provide energy, structural materials, and regulating agents for growth, maintenance, and repair. They are categorized into macronutrients and micronutrients.

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Carbohydrates are the primary source of energy. They include simple sugars like glucose (C6H12O6C_{6}H_{12}O_{6}) and complex polysaccharides like starch and cellulose.

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Proteins are essential for growth and tissue repair. They are polymers made of amino acids linked by peptide bonds. A deficiency can lead to conditions like Kwashiorkor.

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Lipids (Fats and Oils) provide 37 kJ/g37 \text{ kJ/g} of energy, which is more than double the energy density of carbohydrates. They are crucial for cell membrane structure and insulation.

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Vitamins are organic micronutrients. For example, Vitamin C (C6H8O6C_{6}H_{8}O_{6}) is vital for collagen synthesis, and Vitamin D helps in calcium absorption.

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Minerals are inorganic elements. Iron (Fe2+Fe^{2+}) is required for hemoglobin to transport oxygen, and Calcium (Ca2+Ca^{2+}) is needed for bone density and muscle contraction.

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Dietary Fiber (Roughage) consists mainly of cellulose from plant cell walls. It cannot be digested by human enzymes but is essential for peristalsis and preventing constipation.

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A Balanced Diet contains all essential nutrients in correct proportions relative to an individual's age, gender, and physical activity level.

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Energy Balance occurs when energy intake (from food) equals energy expenditure (metabolism and physical activity).

📐Formulae

BMI=mass (kg)(height (m))2BMI = \frac{mass \text{ (kg)}}{(height \text{ (m)})^{2}}

Total Energy (kJ)=(mcarb×17)+(mprotein×17)+(mlipid×37)\text{Total Energy (kJ)} = (m_{carb} \times 17) + (m_{protein} \times 17) + (m_{lipid} \times 37) keywords: mm is mass in grams.

1 kcal=4.184 kJ1 \text{ kcal} = 4.184 \text{ kJ}

💡Examples

Problem 1:

A student has a mass of 60 kg60 \text{ kg} and a height of 1.5 m1.5 \text{ m}. Calculate their Body Mass Index (BMI) and determine if they fall within the healthy range (Healthy range: 18.518.5 to 24.924.9).

Solution:

BMI=601.52BMI = \frac{60}{1.5^{2}} BMI=602.25BMI = \frac{60}{2.25} BMI≈26.67 kg/m2BMI \approx 26.67 \text{ kg/m}^{2}

Explanation:

By applying the BMI formula, we find the value is approximately 26.6726.67. Since this value is greater than 24.924.9, the student is categorized as overweight according to standard BMI scales.

Problem 2:

Calculate the total energy provided by a snack containing 20 g20 \text{ g} of carbohydrates, 5 g5 \text{ g} of protein, and 10 g10 \text{ g} of fat.

Solution:

Energy from Carbs=20 g×17 kJ/g=340 kJ\text{Energy from Carbs} = 20 \text{ g} \times 17 \text{ kJ/g} = 340 \text{ kJ} Energy from Protein=5 g×17 kJ/g=85 kJ\text{Energy from Protein} = 5 \text{ g} \times 17 \text{ kJ/g} = 85 \text{ kJ} Energy from Fat=10 g×37 kJ/g=370 kJ\text{Energy from Fat} = 10 \text{ g} \times 37 \text{ kJ/g} = 370 \text{ kJ} Total Energy=340+85+370=795 kJ\text{Total Energy} = 340 + 85 + 370 = 795 \text{ kJ}

Explanation:

Energy is calculated by multiplying the mass of each macronutrient by its specific energy value (17 kJ/g17 \text{ kJ/g} for carbs/proteins and 37 kJ/g37 \text{ kJ/g} for lipids) and summing the results.

Essential Nutrients and Balanced Diet Grade 9 Notes & Examples