02.04 Monomers, Polymers, and Macromolecules

Question 1

Define macromolecules and explain how they are formed from monomers. (5 marks)

Mark Scheme:

1. Macromolecules are large biological molecules essential for life, including polysaccharides, proteins, and nucleic acids. (1 mark)
2. They are polymers made up of repeating subunits called monomers. (1 mark)
3. Monomers join together via condensation reactions, where a water molecule is removed. (1 mark)
4. This process forms covalent bonds between monomers. (1 mark)
5. Examples: Monosaccharides form polysaccharides, amino acids form proteins, and nucleotides form nucleic acids. (1 mark)

Question 2

Describe the processes of condensation and hydrolysis in biological systems. (6 marks)

Mark Scheme:

1. Condensation reaction: Two monomers join, forming a covalent bond and releasing a molecule of water. (1 mark)
2. This process is responsible for polymerization, forming polymers like polysaccharides, proteins, and nucleic acids. (1 mark)
3. Example: Monosaccharides join via glycosidic bonds to form polysaccharides. (1 mark)
4. Hydrolysis: Breaks polymers into monomers by adding a molecule of water. (1 mark)
5. Example: Proteins are broken down into amino acids by hydrolysis of peptide bonds. (1 mark)
6. These reactions are catalyzed by enzymes in biological systems, ensuring efficiency. (1 mark)

Question 3

Explain the structure and bonding of polysaccharides and their biological importance. (6 marks)

Mark Scheme:

1. Polysaccharides are polymers of monosaccharides linked by glycosidic bonds. (1 mark)
2. They are formed through condensation reactions and broken down by hydrolysis. (1 mark)
3. Structure: Can be linear (e.g., cellulose) or branched (e.g., glycogen). (1 mark)
4. Energy storage: Starch in plants and glycogen in animals store energy. (1 mark)
5. Structural role: Cellulose provides rigidity to plant cell walls. (1 mark)
6. Polysaccharides are insoluble, making them ideal for storage without affecting osmotic balance. (1 mark)

Question 4

Describe the bonds involved in the formation of biological polymers and their significance. (6 marks)

Mark Scheme:

1. Glycosidic bonds link monosaccharides in polysaccharides, providing energy storage and structural support. (1 mark)
2. Peptide bonds connect amino acids in proteins, forming the primary structure of polypeptides. (1 mark)
3. Ester bonds attach fatty acids to glycerol in lipids, crucial for energy storage and membrane structure. (1 mark)
4. These bonds are formed via condensation reactions, making them strong and stable. (1 mark)
5. Hydrolysis of these bonds releases energy or breaks down molecules during digestion. (1 mark)
6. Covalent bonds ensure structural integrity and functionality of macromolecules in cells. (1 mark)

Question 5

Compare the structure and roles of proteins and nucleic acids. (6 marks)

Mark Scheme:

1. Proteins are polymers of amino acids linked by peptide bonds, folded into specific 3D shapes for functionality. (1 mark)
2. They perform structural (e.g., keratin), enzymatic (e.g., amylase), and regulatory (e.g., hormones) roles. (1 mark)
3. Nucleic acids (DNA and RNA) are polymers of nucleotides linked by phosphodiester bonds. (1 mark)
4. DNA stores genetic information, while RNA plays a role in protein synthesis. (1 mark)
5. Proteins are essential for cellular structure and metabolism, while nucleic acids transmit and express genetic information. (1 mark)
6. Both are critical macromolecules, ensuring cellular function and continuity of life. (1 mark)

Question 6

Explain how lipids differ from other macromolecules in structure and function. (6 marks)

Mark Scheme:

1. Unlike polysaccharides, proteins, and nucleic acids, lipids are not true polymers. (1 mark)
2. They are made of fatty acids and glycerol, joined by ester bonds through condensation reactions. (1 mark)
3. Structure: Lipids are hydrophobic, with long nonpolar hydrocarbon chains. (1 mark)
4. Energy storage: Lipids provide long-term energy reserves, yielding more energy per gram than carbohydrates. (1 mark)
5. Membrane structure: Phospholipids form bilayers, creating a selectively permeable barrier in cells. (1 mark)
6. Lipids also function in insulation, protection, and as precursors for hormones like steroids. (1 mark)

Question 7

What are the roles of monosaccharides and amino acids as biological monomers? (5 marks)

Mark Scheme:

1. Monosaccharides (e.g., glucose) are the building blocks of polysaccharides like starch and glycogen. (1 mark)
2. They serve as a quick energy source and storage molecules. (1 mark)
3. Amino acids are the monomers of proteins, linked by peptide bonds through condensation reactions. (1 mark)
4. Proteins perform a wide range of roles, including catalysis, transport, and structural support. (1 mark)
5. Both monomers are essential for cellular metabolism and function. (1 mark)

Question 8

Discuss the significance of natural and synthetic polymers, providing examples. (5 marks)

Mark Scheme:

1. Natural polymers (e.g., cellulose, rubber) are essential for biological processes and structures. (1 mark)
2. Example: Cellulose provides rigidity to plant cell walls, supporting growth. (1 mark)
3. Synthetic polymers (e.g., polyester, PVC) are human-made materials with diverse industrial applications. (1 mark)
4. Example: Nylon is used in textiles due to its strength and elasticity. (1 mark)
5. Both types of polymers demonstrate the versatility of repeating subunit structures for various uses. (1 mark)

Question 9

How do condensation and hydrolysis reactions contribute to metabolism? (6 marks)

Mark Scheme:

1. Condensation reactions build polymers by linking monomers, essential for anabolism (e.g., protein synthesis). (1 mark)
2. Hydrolysis reactions break down polymers into monomers, crucial for catabolism (e.g., digestion of carbohydrates). (1 mark)
3. Both reactions involve the removal or addition of water molecules, respectively. (1 mark)
4. Example: Hydrolysis of starch into glucose provides energy through cellular respiration. (1 mark)
5. Enzymes catalyze these reactions, ensuring efficiency and specificity in metabolic pathways. (1 mark)
6. Together, these processes maintain the balance between energy release and synthesis in cells. (1 mark)

Question 10

Summarize the relationship between monomers, polymers, and macromolecules. (5 marks)

Mark Scheme:

• Monomers are the basic building blocks of biological polymers. (1 mark)
• Polymers are chains of monomers linked by covalent bonds, formed through condensation reactions. (1 mark)
• Macromolecules, such as polysaccharides, proteins, and nucleic acids, are large biological molecules made of polymers. (1 mark)
• Example: Glucose forms starch (polysaccharide), and amino acids form proteins. (1 mark)
• These relationships are fundamental to the structure and function of living organisms. (1 mark)