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Biomolecules - Hormones

Grade 12CBSEChemistry

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

🔑Concepts

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Hormones are chemical messengers produced by endocrine glands in trace amounts and are transported by the bloodstream to target organs to regulate physiological activities.

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Classification based on chemical nature: (i) Steroids (e.g., estrogens, androgens, cortisol), (ii) Polypeptides (e.g., insulin, glucagon, oxytocin), (iii) Amino acid derivatives (e.g., epinephrine, norepinephrine).

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Thyroxine (T4T_4) is an iodinated derivative of the amino acid tyrosine, secreted by the thyroid gland. Deficiency of iodine in the diet leads to Hypothyroidism and enlargement of the thyroid gland, known as Goitre.

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Blood glucose levels are maintained by the antagonistic action of two hormones: Insulin (which lowers blood sugar by converting glucose to glycogen) and Glucagon (which raises blood sugar by mobilizing glucose from glycogen).

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Epinephrine (Adrenaline) and Norepinephrine are 'fight or flight' hormones that prepare the body for emergency situations by increasing heart rate and blood pressure.

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Sex hormones include Androgens (e.g., Testosterone) responsible for male secondary sexual characteristics, and Estrogens and Progesterone responsible for female secondary sexual characteristics and the menstrual cycle.

📐Formulae

Molecular Formula of Thyroxine: C15H11I4NO4\text{Molecular Formula of Thyroxine: } C_{15}H_{11}I_{4}NO_{4}

Molecular Formula of Epinephrine (Adrenaline): C9H13NO3\text{Molecular Formula of Epinephrine (Adrenaline): } C_{9}H_{13}NO_{3}

Glycogen→GlucagonGlucose→InsulinGlycogen\text{Glycogen} \xrightarrow{\text{Glucagon}} \text{Glucose} \xrightarrow{\text{Insulin}} \text{Glycogen}

Tyrosine→IodinationThyroxine (in presence of I2)\text{Tyrosine} \xrightarrow{\text{Iodination}} \text{Thyroxine (in presence of } I_{2} \text{)}

💡Examples

Problem 1:

Identify the hormone that is responsible for maintaining the blood glucose level and specify the gland that secretes it.

Solution:

Insulin and Glucagon.

Explanation:

Insulin and Glucagon are secreted by the pancreas (specifically the Islets of Langerhans). Insulin converts glucose to glycogen when blood sugar is high (>100 mg/dL> 100 \text{ mg/dL}), whereas glucagon converts stored glycogen back to glucose when blood sugar is low.

Problem 2:

Why is the intake of iodized salt recommended for humans?

Solution:

To prevent Goitre and ensure the synthesis of Thyroxine (C15H11I4NO4C_{15}H_{11}I_{4}NO_{4}).

Explanation:

The thyroid gland requires iodine (I2I_{2}) to synthesize the hormone thyroxine. Thyroxine regulates the metabolism of carbohydrates, proteins, and fats. A deficiency of iodine leads to an enlargement of the thyroid gland, a condition called Goitre.

Problem 3:

Classify the following hormones into their chemical categories: Insulin, Testosterone, and Epinephrine.

Solution:

Insulin: Polypeptide; Testosterone: Steroid; Epinephrine: Amino acid derivative.

Explanation:

Insulin is a protein consisting of 5151 amino acids. Testosterone is derived from the cholesterol skeleton (steroid nucleus). Epinephrine is derived from the amino acid tyrosine.