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Biology - Human Anatomy and Physiology (Nutrition, Digestive System, Skeleton, Movement, Skin, Respiratory System)

Grade 9ICSE

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

🔑Concepts

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Nutrition: A process of intake of nutrients like carbohydrates, proteins, fats, vitamins, and minerals. Carbohydrates and fats are energy-giving, proteins are body-building, while vitamins and minerals are protective foods.

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Digestive System: The human alimentary canal is a long tube where digestion occurs via enzymes. Key enzymes include Amylase (starch to maltose), Pepsin (proteins to peptides in acidic pHpH), and Lipase (emulsified fats to fatty acids and glycerol).

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Peristalsis: The rhythmic contraction and relaxation of the muscles of the alimentary canal that pushes food forward.

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Skeleton: Divided into the Axial Skeleton (Skull, Vertebral Column, Ribs) and Appendicular Skeleton (Limbs and Girdles). Bones are held together at joints by ligaments.

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Movement: Facilitated by antagonistic muscles like the Biceps and Triceps. When the Biceps (flexor) contracts, the arm bends; when the Triceps (extensor) contracts, the arm straightens.

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Skin Structure: Composed of the Epidermis (outer layer with MelaninMelanin) and Dermis (inner layer containing sweat glands, sebaceous glands, and hair follicles). It plays a vital role in thermoregulation through vasodilation and vasoconstriction.

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Respiratory System: Includes the nasal cavity, pharynx, larynx, trachea, bronchi, and alveoli. Gas exchange occurs in the alveoli via diffusion where O2O_2 enters the blood and CO2CO_2 leaves it.

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Mechanism of Breathing: Inspiration involves the contraction of the diaphragm and external intercostal muscles, increasing thoracic volume and decreasing pressure. Expiration is the reverse process.

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Cellular Respiration: The chemical breakdown of glucose in cells to release energy in the form of ATPATP (Adenosine Triphosphate).

📐Formulae

C6H12O6+6O2→6CO2+6H2O+38ATPC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 38 ATP

BMI=Mass(kg)[Height(m)]2BMI = \frac{Mass (kg)}{[Height (m)]^2}

VitalCapacity=TidalVolume+InspiratoryReserveVolume+ExpiratoryReserveVolumeVital Capacity = Tidal Volume + Inspiratory Reserve Volume + Expiratory Reserve Volume

Starch+SalivaryAmylase→pH≈6.8MaltoseStarch + Salivary Amylase \xrightarrow{pH \approx 6.8} Maltose

💡Examples

Problem 1:

Calculate the Body Mass Index (BMI) of a student who weighs 60kg60 kg and stands 1.5m1.5 m tall. Categorize their health status if the normal range is 18.518.5 to 24.924.9.

Solution:

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

Explanation:

Since the calculated BMIBMI is 26.6726.67, which is greater than the 24.924.9 upper limit, the student is categorized as overweight.

Problem 2:

During vigorous exercise, why do we experience muscle cramps? Represent the chemical reaction involved.

Solution:

Muscle cramps occur due to anaerobic respiration in muscle cells, leading to the accumulation of Lactic Acid: C6H12O6→2C3H6O3(LacticAcid)+2ATPC_6H_{12}O_6 \rightarrow 2C_3H_6O_3 (Lactic Acid) + 2ATP

Explanation:

When oxygen supply is insufficient (O2O_2 debt), glucose is partially broken down into lactic acid, causing fatigue and cramps.

Problem 3:

Identify the role of the liver in digestion and how it handles excess glucose.

Solution:

The liver secretes bile (no enzymes) to emulsify fats. Excess glucose is converted into glycogen for storage: Glucose→InsulinGlycogenGlucose \xrightarrow{Insulin} Glycogen

Explanation:

Bile increases the surface area for lipase action, and glycogenesis regulates blood sugar levels.