All Free Biology MCQs with Answers

4651. Some _ provide insulation against atmospheric heat and cold.

• A. Lipids
• B. Carbohydrates
• C. Nucleic acids
• D. Proteins

Explanation: The correct answer is Option A: Lipids. Lipids provide thermal insulation by forming a barrier that reduces heat exchange, allowing organisms to maintain a stable internal temperature. Fats and oils, which are types of lipids, are particularly effective in this role due to their low thermal conductivity. On the other hand, carbohydrates are primarily energy sources, nucleic acids are involved in genetic functions, and proteins have various roles but are not specialized for thermal insulation.

4652. Triacylglycerols are also called as:

• A. Phospholipids or sphingolipids
• B. Glycerolipids or fatty acids
• C. Triglycerides or neutral lipids
• D. Steroids or cholesterol

Explanation: The correct answer is Option C: Triacylglycerols are also called triglycerides or neutral lipids. These molecules consist of three fatty acid chains esterified to a glycerol backbone, making them a primary form of energy storage in animals. They are termed 'neutral' due to their nonpolar nature, which makes them hydrophobic and efficient at storing energy.Option A is incorrect because phospholipids and sphingolipids are different classes of lipids with distinct functions, primarily in cellular membranes.Option B is partially correct because it mentions glycerolipids, which include triacylglycerols, but also includes fatty acids, which are components of various lipids rather than a synonym for triacylglycerols. Option D is incorrect as it mentions steroids and cholesterol, which are structurally and functionally different from triacylglycerols.

4653. _ is composed of one glycerol and three fatty acids.

• A. Acylglycerol
• B. Triglyceride
• C. Monoglyceride
• D. Diacylglycerol

Explanation: The correct answer is Option B: Triglyceride. Triglycerides are composed of one glycerol molecule and three fatty acids, making them the primary form of fat storage in the body. They provide a concentrated source of energy and help with insulation. Option A, acylglycerol, is a general term that encompasses different types of glycerol and fatty acid structures, not specifically three fatty acids. Option C, monoglyceride, involves only one fatty acid, while Option D, diacylglycerol, includes two fatty acids. Therefore, neither matches the structure described in the question.

4654. Pick up the character which does not belong to unsaturated fatty acids:

• A. No double bond
• B. Presence of multiple double bonds
• C. Low melting point
• D. Commonly found in plant fats

Explanation: The correct option is A) No double bond. Unsaturated fatty acids are defined by the presence of one or more double bonds in their carbon chains. This structural characteristic differentiates them from saturated fatty acids, which do not have double bonds. Option B) Presence of multiple double bonds, Option C) Low melting point, and Option D) Commonly found in plant fats are all properties associated with unsaturated fatty acids, hence they do belong to this category.

4655. Melting point of butyric acid is:

• A. 61.3oC
• B. 63.1oC
• C. 80oC
• D. -8oC

Explanation: Butyric acid is a short-chain fatty acid with four carbon atoms, which results in a relatively low melting point of approximately -8°C. The other options represent melting points typical of longer-chain, more complex fatty acids. Therefore, these values are too high to be applicable to butyric acid.

4656. A saturated fatty acid with four carbon atoms is:

• A. Oleic acid
• B. Palmitic acid
• C. Butyric acid
• D. Acetic acid

Explanation: The correct answer is Butyric acid, which is a saturated fatty acid with 4 carbon atoms, as indicated by the 'but-' prefix in its name. Other options have either more carbon atoms or are unsaturated. Oleic acid is unsaturated and has 18 carbon atoms. Palmitic acid is saturated but has 16 carbon atoms. Acetic acid, while saturated, has only 2 carbon atoms.

4657. _ fats are solid at room temperature.

• A. Saturated
• B. Unsaturated
• C. All
• D. None

Explanation: Saturated fats are solid at room temperature because their molecular structure is straight and allows for tight packing, which is typical of animal fats. Unsaturated fats, however, have kinks in their structure that prevent them from packing tightly, causing them to be liquid at room temperature, which is typical of plant oils. Therefore, the correct answer is that saturated fats are solid at room temperature, distinguishing them from unsaturated fats.

4658. Fats and oils are:

• A. Lighter than water
• B. Heavier than water
• C. Less viscous than water
• D. More denser than water

Explanation: Fats and oils have a specific gravity of about 0.8. That is why they are lighter and have a lower density than water.

4659. Glycerol, fatty acids and phosphoric acid gives rise to:

• A. Phospholipid
• B. Phosphatidic acid
• C. Phosphatidylcholine
• D. Phosphatidylethanolamine

Explanation: The correct answer is phosphatidic acid. When glycerol, fatty acids, and phosphoric acid combine, they form phosphatidic acid, which is the simplest phospholipid and serves as a precursor for more complex lipids such as phospholipids. Phospholipids like phosphatidylcholine and phosphatidylethanolamine require additional components, such as a nitrogenous base (choline or ethanolamine, respectively), which are not part of the initial combination described in the question.

4660. Phosphatidic acid upon combining with a nitrogenous base gives rise to:

• A. Phosphatidic acid
• B. Phosphatidylcholine
• C. Phospholipid
• D. Lecithin

Explanation: The correct answer is Phosphatidylcholine. When phosphatidic acid combines with a nitrogenous base like choline, it forms phosphatidylcholine, a specific type of phospholipid that is abundant in cell membranes. Phosphatidic acid is incorrect because it does not itself combine with a nitrogenous base; it is a precursor. Phospholipid is too broad of an answer, as it refers to the general class of molecules formed, not the specific one created by this reaction. Lecithin is a mixture of phospholipids.