Question 1: What is the general formula for an alkane?

• CₙH₂ₙ.
• CₙH₂ₙ₋₂.
• CₙH₂ₙ₊₄. (Correct answer)
• CₙH₂ₙ₋₄.

Correct answer: CₙH₂ₙ₊₄.

The general formula for an alkane is CnH2n+2, where 'n' represents the number of carbon atoms. This formula describes saturated hydrocarbons containing only single carbon-carbon and carbon-hydrogen bonds, ensuring that each carbon atom forms four bonds. The provided option C, CnH2n+4, is not the standard general formula for alkanes.

Question 2: What is the functional group of alcohols?

• -OH.
• -COOH.
• -NH₂.
• -CH₃.

The functional group characteristic of alcohols is the hydroxyl group, represented as -OH. This group consists of an oxygen atom covalently bonded to a hydrogen atom, and it is attached to a carbon atom within an organic molecule. The presence of the hydroxyl group dictates many of the chemical and physical properties of alcohols.

Question 3: What type of reaction is involved in the conversion of an alkene to an alkane?

• Hydrolysis.
• Hydrogenation. (Correct answer)
• Polymerization.
• Substitution.

Correct answer: Hydrogenation.

The conversion of an alkene to an alkane involves a hydrogenation reaction. In this process, hydrogen gas (H₂) is added across the carbon-carbon double bond of the alkene, typically in the presence of a metal catalyst like platinum, palladium, or nickel. This addition reaction saturates the hydrocarbon, transforming the alkene into a single-bonded alkane.

Question 4: What is a peptide bond?

• A bond between two glucose molecules.
• A bond between the nitrogen and hydrogen in amino acids.
• A bond between the carboxyl group of one amino acid and the amino group of another amino acid. (Correct answer)
• A bond between two fatty acids.

Correct answer: A bond between the carboxyl group of one amino acid and the amino group of another amino acid.

A peptide bond is a covalent bond formed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another amino acid. This bond is formed through a condensation reaction, where a molecule of water is removed. Peptide bonds are fundamental to linking amino acids together to form polypeptide chains and ultimately proteins.

Question 5: What is the primary function of enzymes in biochemical reactions?

• To slow down reactions.
• To provide energy for the reaction.
• To catalyze reactions and increase the reaction rate. (Correct answer)
• To convert products into reactants.

Correct answer: To catalyze reactions and increase the reaction rate.

Enzymes are biological catalysts that significantly increase the rate of biochemical reactions without being consumed in the process. They achieve this by lowering the activation energy required for the reaction to proceed. Each enzyme is highly specific, typically catalyzing only one or a few related reactions.

Question 6: What is the general structure of a fatty acid?

• A ring of carbon atoms.
• A long hydrocarbon chain with a carboxyl group at one end. (Correct answer)
• A glycerol molecule with two hydroxyl groups.
• A nitrogen-containing group attached to a hydrocarbon.

Correct answer: A long hydrocarbon chain with a carboxyl group at one end.

A fatty acid is characterized by a long hydrocarbon chain, which is typically unbranched and can be saturated or unsaturated, attached to a carboxyl group (-COOH) at one end. The hydrocarbon chain is hydrophobic, while the carboxyl group is hydrophilic. This structure allows fatty acids to form lipids and serve as energy storage molecules.

Question 7: Which of the following is an example of a monosaccharide?

• Glucose. (Correct answer)
• Sucrose.
• Starch.
• Lactose.

Correct answer: Glucose.

Glucose is classified as a monosaccharide because it is a simple sugar, meaning it is the most basic unit of carbohydrates and cannot be hydrolyzed into smaller sugar units. In contrast, sucrose and lactose are disaccharides (two sugar units), and starch is a polysaccharide (many sugar units).

Question 8: What type of bond holds the two strands of DNA together?

• Ionic bonds.
• Covalent bonds.
• Hydrogen bonds. (Correct answer)
• Disulfide bonds.

Correct answer: Hydrogen bonds.

The two strands of DNA are held together by hydrogen bonds, which form between complementary nitrogenous bases: adenine (A) with thymine (T), and guanine (G) with cytosine (C). These weak intermolecular forces allow the strands to separate easily during processes like DNA replication and transcription, while covalent bonds form the strong sugar-phosphate backbone of each individual strand.

Question 9: What is the main difference between saturated and unsaturated fats?

• Saturated fats have fewer carbon atoms.
• Saturated fats have no double bonds, while unsaturated fats have one or more double bonds. (Correct answer)
• Saturated fats are liquid at room temperature.
• Unsaturated fats are solid at room temperature.

Correct answer: Saturated fats have no double bonds, while unsaturated fats have one or more double bonds.

The main difference between saturated and unsaturated fats lies in their chemical structure, specifically the presence of double bonds in their fatty acid chains. Saturated fats contain only single bonds between carbon atoms, making them 'saturated' with hydrogen, while unsaturated fats have one or more double bonds, which create kinks in the chain and affect their physical properties.