Chapter – 2A : Levels Of Organisation Of Life | Chapter Solution Class 9

(a) Glucose

Explanation: Glucose (C₆H₁₂O₆) is a monosaccharide and a primary source of energy for living organisms. It is also known as dextrose and is involved in cellular respiration to produce ATP. Sucrose (C₁₂H₂₂O₁₁) is a disaccharide composed of glucose and fructose. Maltose (C₁₂H₂₂O₁₁) consists of two glucose molecules, and Lactose (C₁₂H₂₂O₁₁) consists of glucose and galactose.

(d) Vitamin-C

Explanation: Vitamin C (Ascorbic Acid) is a water-soluble vitamin and acts as an antioxidant. It is essential for collagen synthesis, wound healing, and boosting the immune system. Unlike fat-soluble vitamins (A, D, E, and K), water-soluble vitamins dissolve in water and are not stored in the body, requiring regular intake.

(b) Valine

Explanation: Essential amino acids cannot be synthesized by the human body and must be obtained through diet. Valine is one of the nine essential amino acids required for muscle growth, tissue repair, and nitrogen balance. On the other hand, Tyrosine, Glycine, and Alanine are non-essential amino acids, meaning they can be synthesized by the body.

(b) Uracil

Explanation: Pyrimidines are nitrogenous bases found in nucleic acids. They have a single-ring structure. Uracil (U), Cytosine (C), and Thymine (T) are pyrimidines. Adenine (A) and Guanine (G) are purines, which have a double-ring structure. Uracil is found only in RNA, replacing Thymine (T) in DNA.

(d) Sulphur (S)

Explanation: Trace elements are minerals required in small amounts (less than 0.01g per day) but are essential for biological functions. Sulphur (S) is a trace element needed for protein synthesis, enzyme function, and detoxification. Calcium (Ca) and Magnesium (Mg) are macro-elements, meaning they are required in larger amounts. Copper (Cu) is also a trace element, but sulphur is more significant in body functions.

(c) Vitamin-C

Explanation: Ascorbic acid is another name for Vitamin C, which is essential for collagen synthesis, immune function, and antioxidant protection. A deficiency of Vitamin C leads to scurvy, a disease characterized by bleeding gums, weakness, and slow wound healing. Unlike fat-soluble vitamins (A, D, E, K), Vitamin C is water-soluble and must be consumed regularly through diet.

1. Vitamin C
2. Acetic acid
3. 4 kcal/g
4. Double
5. Calcium (Ca)
6. Ribose

False (Ribose is a component of RNA, not DNA.)

True (Fats provide the highest energy yield per gram.)

False (The pH of a neutral solution is 7.0, not 7.4.)

False (Carbohydrates are composed of carbon, hydrogen, and oxygen, not nitrogen.)

True (Amino acids are linked by peptide bonds to form proteins.)

Lactose

Reason: Glucose, Fructose, and Galactose are monosaccharides (simple sugars), while Lactose is a disaccharide (made up of glucose and galactose).

Amino acid

Reason: Monosaccharides, Disaccharides, and Polysaccharides are carbohydrates, whereas Amino acids are the building blocks of proteins, making it the odd one out.

Boron (B)

Reason: Calcium (Ca), Magnesium (Mg), and Phosphorus (P) are macro-elements, which are required in large amounts by the body, whereas Boron (B) is a micro-element (trace element), required in small amounts.

Ribonucleic Acid

Scurvy

Retinol

Nitrogen (N)

Phosphorus (P), Magnesium (Mg)

An acid is a substance that dissociates in water to release hydrogen ions (H⁺), increasing the H⁺ concentration in a solution. Acids generally have a sour taste and a pH lower than 7.

Example: Hydrochloric acid (HCl), Acetic acid (CH₃COOH).

A salt is a chemical compound formed when an acid reacts with a base in a neutralization reaction. It consists of positive metal ions (cations) and negative non-metal ions (anions).

Example: Sodium chloride (NaCl), Potassium sulfate (K₂SO₄).

Proteins are large biomolecules made up of amino acids joined by peptide bonds. They play a vital role in growth, repair, and enzyme formation in living organisms.

Example: Hemoglobin, Insulin, Enzymes.

The two biological importance of water in plant cells are:

1. Water is essential for photosynthesis, providing hydrogen ions (H⁺) for glucose formation.
2. Water helps in the transport of nutrients and minerals from the soil to various parts of the plant.

The two importance of calcium are:

1. Calcium is essential for bone and teeth formation in humans and animals.
2. Calcium plays a crucial role in muscle contraction and blood clotting.

Essential Amino Acids

Essential amino acids cannot be synthesized by the human body and must be obtained through diet. The nine essential amino acids are:

• Leucine
• Isoleucine
• Valine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Histidine (essential for infants)

Biological Importance of Fats

1. Energy Storage – Fats are the most concentrated source of energy, providing 9 kcal/g.
2. Structural Role – Fats are major components of cell membranes (phospholipids).
3. Insulation and Protection – Stored fats help maintain body temperature and protect organs.

Water-Soluble Vitamins

Water-soluble vitamins dissolve in water and are not stored in the body, requiring regular intake. These include:

1. Vitamin B-complex (B1, B2, B3, B5, B6, B7, B9, B12)
2. Vitamin C (Ascorbic Acid)

Deficiency Symptoms of Water-Soluble Vitamins

General Role of Vitamin B

1. Energy Production – Helps break down carbohydrates, fats, and proteins for energy.
2. Nervous System Function – Supports brain function and nerve signaling.
3. Red Blood Cell Formation – Important for preventing anemia.
4. DNA Synthesis and Cell Growth – Essential for cell division and repair.

Deficiency Symptoms of Vitamin B

• Beri-Beri (Vitamin B₁ deficiency) – Muscle weakness, nerve issues.
• Pellagra (Vitamin B₃ deficiency) – Dermatitis, diarrhea, dementia.
• Pernicious anemia (Vitamin B₁₂ deficiency) – Fatigue, nerve problems.

Proteins are macromolecules made up of amino acids and are essential for growth, repair, and metabolic functions in the body.

Biological Importance of Proteins

1. Growth and Repair – Proteins help in cell growth, muscle repair, and wound healing.
2. Enzyme Formation – Almost all enzymes are proteins that catalyze biochemical reactions.
3. Hormone Production – Proteins help synthesize hormones like insulin and growth hormones.
4. Immune System Function – Antibodies that fight infections are proteins.
5. Structural Role – Collagen and keratin provide strength to skin, hair, and nails.
6. Transport Function – Hemoglobin (a protein) carries oxygen in the blood.
7. Energy Source – When carbohydrates and fats are unavailable, proteins can be broken down for energy.