All Free Biology MCQs with Answers

4571. Starch forms a _ helical structure that can hold a _ molecule and gives a blue color:

• A. Primary, I₂
• B. Secondary, I₂
• C. Tertiary, I₂
• D. Quaternary, I₂

Explanation: Starch forms a secondary helical structure that can trap iodine (I₂), resulting in a blue color.

4572. A common carbohydrate composed of glucose and fructose joined by a linkage between C-1 of glucose and C-2 of fructose is:

• A. Starch
• B. Maltose
• C. Lactose
• D. Sucrose

Explanation: Sucrose is a common carbohydrate (disaccharide) composed of glucose and fructose. In sucrose, glucose and fructose are linked by a glycosidic bond between C-1 of glucose and C-2 of fructose.

4573. A triose aldo sugar is:

• A. Dihydroxyacetone
• B. Cellulose
• C. Glyceraldehyde
• D. Fructose

Explanation: Glyceraldehyde is a triose sugar with an aldehyde group, making it an aldo sugar.

4574. For the synthesis of 10 gm of glucose, plants use solar energy of about:

• A. 574 kcal/ g m
• B. 550 kcal/ g m
• C. 717.6 kcal / g m
• D. 717.6 kcal/ g ml

Explanation: The synthesis of 1gram of glucose via photosynthesis requires roughly 71.76kcal of solar energy. For 10g of glucose the total energy is the same value expressed in kcal (not per gram), hence 717.6kcal is the energy needed for 10g of glucose.

4575. Nucleotides are building blocks of nucleic acids. Each nucleotide is a composite molecule made of:

• A. Base­ sugar ­phosphate
• B. Base ­sugar­ OH
• C. Base­s
• D. Sugar ­phosphate

Explanation: A nucleotide is composed of a nitrogenous base, a pentose sugar, and a phosphate group.

4576. A reducing sugar is that which has:

• A. Free aldehyde group
• B. Free aldehyde or ketone group
• C. Free ketone group
• D. None of these

Explanation: A reducing sugar must have a free aldehyde or ketone group that can participate in redox reactions.

4577. Amino acids are arranged in proper sequence during protein synthesis according to the instructions transcribed on:

• A. Transfer RNA (tRNA)
• B. Ribosomal RNA (rRNA)
• C. Messenger RNA (mRNA)
• D. DNA

Explanation: mRNA carries the genetic instructions from DNA to the ribosome, where it directs the sequence of amino acids in protein synthesis.

4578. If in lipids, there is a higher proportion of unsaturated fatty acids, then it will be:

• A. Oils
• B. Waxes
• C. Phenols
• D. Fats

Explanation: Oils are typically liquid at room temperature and contain a higher proportion of unsaturated fatty acids.

4579. Terpenoids are an important group of compounds that are made up of simple repeating units called

• A. Acylglycerols
• B. Isoprenoids
• C. Phospholipids
• D. Ketones

Explanation: Terpenoids (also called isoprenoids) are a large group of natural compounds made up of repeating units of isoprene (a 5-carbon structure). These compounds include essential oils, carotenoids, and steroids.

4580. Melting point of palmitic acid is:

• A. -8 °C
• B. 8oC
• C. 63.1oC
• D. 56 °C

Explanation: Palmitic acid is a saturated long-chain fatty acid with 16 carbon atoms. Its melting point is relatively high, about 63.1 °C, due to the strong van der Waals forces between its long hydrocarbon chains.