All Free Biology MCQs with Answers

2081. Triglyceride is also known as_____________?

• A. Natural lipid
• B. Neutral lipid
• C. Neutral wax
• D. All of these

Explanation: A triglyceride is formed when glycerol combines with three fatty acids, and it is called a neutral lipid because it has no charged ionic groups. Neutral wax is a different type of lipid made from a fatty acid and a long-chain alcohol. Students may choose natural lipid because triglycerides occur naturally, but the precise biochemical term among the options is neutral lipid.

2082. In esterification OH comes from_______________?

• A. Organic acid
• B. Alcohol
• C. Water
• D. Sugar

Explanation: During esterification, the hydroxyl group that remains in the ester-forming reaction comes from the alcohol, while the acid contributes its carbonyl-containing acyl group; water is released overall. The likely mistake is water, because water is a product of condensation rather than the source of the alcohol hydroxyl group in the textbook reaction.

2083. Which one is not found in fatty acids in acylglycerols____________?

• A. C-6
• B. C-25
• C. C-26
• D. C-30

Explanation: Fatty acids in ordinary acylglycerols generally have an even number of carbon atoms because they are assembled from two-carbon units, whereas C-25 is odd. The likely mistake is C-30, because it is a long chain, but its even carbon number does not violate the usual pattern.

2084. Animals fats are ______________ atroom temperature?

• A. Liquids
• B. Gases
• C. Solids
• D. None of these

Explanation: Animal fats usually contain a high proportion of saturated fatty acids, whose straight chains pack closely and remain solid at room temperature. The likely mistake is liquids, which more commonly describes oils rich in unsaturated fatty acids.

2085. Which one the following fatty acid is more soluble in an organic solvent and has higher melting point____________?

• A. Acetic acid
• B. Butyric acid
• C. Palmitic acid
• D. All have same

Explanation: Palmitic acid has the longest hydrocarbon chain among the choices, so its nonpolar part interacts well with organic solvents, and its long, straight chains pack tightly to produce the highest melting point. A student may choose acetic acid because it is the smallest and most familiar fatty acid, but a short chain gives a lower melting point and greater water solubility, not the highest melting point.

2086. Which of the following statement is incorrect5 for fats containing unsaturated fatty acid_____________?

• A. They contain double bond
• B. They are usually solid at room temperature
• C. They are lighter than water
• D. Their specific gravity is less than 1Exploring Local Private K-12 Schools

Explanation: Unsaturated fatty acids contain one or more double bonds that introduce bends in their chains, preventing tight packing and making their fats usually liquid at room temperature. Students may choose the density statement, but fats are generally lighter than water, so their specific gravity is less than 1.

2087. Fatty acids containing 18 C atoms and a single double bond is____________?

• A. Saturated Fatty acid
• B. Unsaturated fatty acid
• C. Oleic Acid
• D. Plamitic acid

Explanation: Oleic acid is an 18-carbon fatty acid with one double bond, written as C18:1. Palmitic acid is the likely alternative because it is also a common long-chain fatty acid, but it is saturated and contains 16 carbon atoms, not 18.

2088. Lipid molecules can store double amount of energy as compared to same amount of carbohydrate because of high number of__________________?

• A. C-C bonds
• B. C-H bonds
• C. C-N bonds
• D. C-O bonds

Explanation: Lipids contain many reduced C-H bonds, and oxidation of these bonds releases substantial energy; this is why fats yield about twice as much energy per gram as carbohydrates. Students may choose C-C bonds because carbon chains are prominent in lipids, but the greater energy yield mainly reflects the abundance of hydrogen and C-H bonds.

2089. Lipids are soluble in which of the following_______________?

• A. Water
• B. Ether
• C. All solvents
• D. Not in any of the above

Explanation: Lipids are largely nonpolar, so they dissolve in nonpolar organic solvents such as ether but do not dissolve well in polar water. Students may choose “all solvents” because different lipids have different properties, but the general solubility rule is that lipids dissolve in organic solvents.

2090. Which of the following substance is most favorable to form structural component of biological membranes___________?

• A. Hydrophilic Carbohydrates
• B. Hydrophobic fats.
• C. Both a and b
• D. None of these

Explanation: Membrane structure is based mainly on amphipathic lipids, whose hydrophobic portions form the interior barrier and whose hydrophilic portions face water. Hydrophilic carbohydrates alone cannot form the main membrane bilayer, so students may incorrectly choose both a and b.