ROUTERA


Chapter 14 Biomolecules

Class 12th Chemistry Chapter Case Study


Case Study 1: Structure and Functions of Carbohydrates

Case: Carbohydrates are one of the primary macromolecules found in living organisms, and they are the most abundant source of energy. Simple carbohydrates, such as glucose, are used directly for energy, while complex carbohydrates, like starch and glycogen, act as energy reserves. The basic structural units of carbohydrates are monosaccharides, which can combine to form disaccharides and polysaccharides. Glucose (C₆H₁₂O₆) is an important monosaccharide that provides energy in cellular respiration. The storage forms of glucose, starch in plants, and glycogen in animals, serve as energy reserves.

Questions:

  1. Which of the following is a monosaccharide?

    • A) Sucrose
    • B) Fructose
    • C) Lactose
    • D) Maltose
    • Answer: B) Fructose
  2. Glycogen is the storage form of glucose in:

    • A) Plants
    • B) Fungi
    • C) Animals
    • D) Algae
    • Answer: C) Animals
  3. The polymer of glucose that is used for energy storage in plants is:

    • A) Starch
    • B) Glycogen
    • C) Cellulose
    • D) Chitin
    • Answer: A) Starch
  4. Which of the following is a disaccharide?

    • A) Glucose
    • B) Sucrose
    • C) Fructose
    • D) Galactose
    • Answer: B) Sucrose

Case Study 2: Proteins and Their Functions

Case: Proteins are complex molecules made up of amino acids and are vital for the structure, function, and regulation of cells, tissues, and organs. Enzymes, antibodies, and hormones are all types of proteins with specific functions. The sequence of amino acids in a protein determines its structure and function. The four levels of protein structure are primary, secondary, tertiary, and quaternary. For example, hemoglobin, a quaternary structure protein, carries oxygen in the blood, while enzymes like amylase catalyze the breakdown of starch into sugars.

Questions:

  1. The primary structure of a protein is determined by:

    • A) The arrangement of its amino acids
    • B) The folding of the polypeptide chain
    • C) The interaction between different polypeptide chains
    • D) The secondary structure of the protein
    • Answer: A) The arrangement of its amino acids
  2. Which of the following is NOT a function of proteins?

    • A) Catalysis of biochemical reactions
    • B) Genetic information storage
    • C) Structural support
    • D) Immune defense
    • Answer: B) Genetic information storage
  3. The functional form of hemoglobin is:

    • A) A single polypeptide chain
    • B) Two polypeptide chains
    • C) A quaternary structure of four polypeptide chains
    • D) A double helix
    • Answer: C) A quaternary structure of four polypeptide chains
  4. Which of the following proteins acts as a biological catalyst?

    • A) Antibody
    • B) Hemoglobin
    • C) Amylase
    • D) Collagen
    • Answer: C) Amylase

Case Study 3: Nucleic Acids and Genetic Information

Case: Nucleic acids, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are essential for the storage, transmission, and expression of genetic information. DNA is a double-stranded helix, while RNA is single-stranded. DNA stores the genetic blueprint, while RNA is involved in protein synthesis. DNA consists of four nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G), which pair specifically (A with T, C with G). RNA contains uracil (U) instead of thymine. The process of transcription involves the synthesis of RNA from DNA, and translation is the synthesis of proteins from RNA.

Questions:

  1. Which of the following pairs of nitrogenous bases are found in DNA?

    • A) Adenine and Uracil
    • B) Thymine and Cytosine
    • C) Adenine and Thymine
    • D) Guanine and Uracil
    • Answer: C) Adenine and Thymine
  2. The process of transcription in protein synthesis involves the synthesis of:

    • A) Proteins
    • B) RNA
    • C) DNA
    • D) Amino acids
    • Answer: B) RNA
  3. The function of mRNA in protein synthesis is to:

    • A) Carry amino acids to the ribosome
    • B) Form the ribosomal subunits
    • C) Carry the genetic information from DNA to the ribosome
    • D) Act as a catalyst for protein synthesis
    • Answer: C) Carry the genetic information from DNA to the ribosome
  4. Which of the following is true about RNA?

    • A) RNA is double-stranded
    • B) RNA contains thymine (T)
    • C) RNA is synthesized from DNA during transcription
    • D) RNA does not play a role in protein synthesis
    • Answer: C) RNA is synthesized from DNA during transcription

Case Study 4: Lipids and Their Functions

Case: Lipids are hydrophobic or amphiphilic molecules that play a variety of essential roles in the body, including energy storage, insulation, and the formation of cell membranes. The most common types of lipids are triglycerides, phospholipids, and sterols. Triglycerides are made up of one glycerol molecule and three fatty acids. Phospholipids, which contain a phosphate group, are key components of cell membranes, forming bilayers that separate the internal cell environment from the external environment. Steroids, such as cholesterol, are important in maintaining cell membrane fluidity and are precursors to hormones.

Questions:

  1. The primary function of triglycerides in the human body is:

    • A) To form cell membranes
    • B) To store energy
    • C) To act as hormones
    • D) To regulate metabolism
    • Answer: B) To store energy
  2. Which of the following is a characteristic of phospholipids?

    • A) They contain a hydrophilic head and hydrophobic tail
    • B) They are used for energy storage
    • C) They are not part of cell membranes
    • D) They are involved in muscle contraction
    • Answer: A) They contain a hydrophilic head and hydrophobic tail
  3. Cholesterol is an example of which type of lipid?

    • A) Triglyceride
    • B) Phospholipid
    • C) Steroid
    • D) Fatty acid
    • Answer: C) Steroid
  4. Which of the following is true about lipids?

    • A) Lipids are soluble in water
    • B) Lipids are primarily used as an energy source in cells
    • C) All lipids are found in cell membranes
    • D) Lipids are made up of amino acids
    • Answer: B) Lipids are primarily used as an energy source in cells

Case Study 5: Vitamins and Their Role in Metabolism

Case: Vitamins are organic compounds that are essential for normal growth and metabolism. They are required in small quantities for various biochemical processes in the body. There are two types of vitamins: fat-soluble (A, D, E, and K) and water-soluble (B-complex and C). Fat-soluble vitamins are stored in the liver and fatty tissues, while water-soluble vitamins are not stored and need to be replenished regularly. For example, Vitamin C (ascorbic acid) plays a role in collagen synthesis and acts as an antioxidant, while Vitamin D helps in calcium absorption and bone health.

Questions:

  1. Which of the following vitamins is water-soluble?

    • A) Vitamin A
    • B) Vitamin D
    • C) Vitamin E
    • D) Vitamin C
    • Answer: D) Vitamin C
  2. Vitamin D is important for:

    • A) Vision
    • B) Collagen synthesis
    • C) Calcium absorption
    • D) Antioxidant activity
    • Answer: C) Calcium absorption
  3. Which of the following vitamins is a fat-soluble vitamin?

    • A) Vitamin C
    • B) Vitamin B12
    • C) Vitamin A
    • D) Vitamin B6
    • Answer: C) Vitamin A
  4. Deficiency of which vitamin leads to scurvy?

    • A) Vitamin A
    • B) Vitamin B12
    • C) Vitamin C
    • D) Vitamin D
    • Answer: C) Vitamin C