Biomolecules (B1.1, A1.2, B1.2)

What type of bond links monosaccharides together to form disaccharides?

• Hydrogen bond

• Ionic bond

• Glycosidic bond

• Peptide bond

Answer explanation

A glycosidic bond is the specific type of covalent bond that links monosaccharides together to form disaccharides, allowing for the formation of complex carbohydrates.

Which of the following is a polysaccharide?

• Glucose

• Fructose

• Glycogen

• Sucrose

Answer explanation

Glycogen is a polysaccharide, which is a complex carbohydrate made up of many glucose units. In contrast, glucose and fructose are monosaccharides, while sucrose is a disaccharide composed of glucose and fructose.

What is the primary function of carbohydrates in cells?

• Energy storage and structural support

• Catalyzing biochemical reactions

• Storing genetic information

• Forming cell membranes

Answer explanation

Carbohydrates primarily function in cells for energy storage and providing structural support, such as in cell walls of plants (cellulose) and as energy reserves (glycogen in animals).

Which of the following is true about lipids?

• They are insoluble in water but soluble in organic solvents

• They are formed by the polymerization of fatty acids

• They are polar molecules

• They are composed mainly of nitrogen and carbon

Answer explanation

Lipids are characterized by their insolubility in water and solubility in organic solvents, making the first choice true. They are not formed by polymerization of fatty acids, are not polar, and do not primarily consist of nitrogen.

Which of the following molecules is the main component of cell membranes?

• Cholesterol

• Phospholipids

• Glycogen

• Starch

Answer explanation

Phospholipids are the main component of cell membranes, forming a bilayer that provides structure and regulates the movement of substances in and out of the cell. Cholesterol, glycogen, and starch serve different functions.

What is the role of nucleic acids in cells?

• To provide energy for metabolic processes

• To store and transmit genetic information

• To act as catalysts in biochemical reactions

• To serve as building blocks for proteins

Answer explanation

Nucleic acids, such as DNA and RNA, are essential for storing and transmitting genetic information, which is crucial for cell function and heredity. This makes 'to store and transmit genetic information' the correct choice.

Which of the following bases is found only in RNA?

• Adenine

• Cytosine

• Thymine

• Uracil

Answer explanation

Uracil is the base found only in RNA, replacing thymine, which is found in DNA. Adenine and cytosine are present in both RNA and DNA.

What type of bond joins amino acids together to form proteins?

• Glycosidic bond

• Hydrogen bond

• Peptide bond

• Ionic bond

Answer explanation

Amino acids are linked together by peptide bonds, which form during a dehydration reaction between the amino group of one amino acid and the carboxyl group of another. This is essential for protein synthesis.

Which of the following is an example of a structural protein?

• Hemoglobin

• Keratin

• Insulin

• Amylase

Answer explanation

Keratin is a structural protein found in hair, nails, and skin, providing strength and protection. In contrast, hemoglobin is involved in oxygen transport, insulin regulates blood sugar, and amylase aids in digestion.

Which of the following biomolecules is hydrophobic?

• Carbohydrates

• Lipids

• Nucleic acids

• Proteins

Answer explanation

Lipids are hydrophobic biomolecules, meaning they do not mix well with water. In contrast, carbohydrates, nucleic acids, and proteins are generally hydrophilic or have hydrophilic regions, making lipids the correct choice.