All Free Biology MCQs with Answers

1421. In chlorophytes the main energy stores are__________?

• A. Cellulose
• B. Starch
• C. Glycogen
• D. All of these

Explanation: Green algae store photosynthetic carbohydrate mainly as starch, often in association with their chloroplasts. Glycogen is the common storage carbohydrate in fungi and animals, so students may choose c by applying the storage pattern of those groups to algae.

1422. All of the insectivorous plants are true________________?

• A. Heterotrophs
• B. Autotrophes
• C. Carnivores
• D. Saprotrophs

Explanation: Insectivorous plants carry out photosynthesis and make their own carbohydrates, so they remain autotrophs. They trap insects mainly to obtain nitrogen and other minerals, not to obtain their main energy supply. The likely mistake is choosing carnivores because these plants digest animal tissue.

1423. The monosaccharide found in some bacteria and occurring rarely are______________?

• A. Trioses
• B. Hexoses
• C. Tetroses
• D. Pentoses

Explanation: Tetroses are four-carbon monosaccharides and are relatively rare, occurring in some bacteria and in a few metabolic pathways. Trioses, pentoses and hexoses are more commonly discussed because they participate widely in cellular metabolism and nucleic-acid or energy-related structures. Students may choose pentoses or hexoses because they are familiar biological sugars, but the clue that the sugars are rare points to tetroses.

1424. In Cx(H2O)y x ranges from______________?

• A. 1 to 3 thousand
• B. 3 to many thousand
• C. 3 to 5 thousand
• D. 5 to 9 thousand

Explanation: In the general formula Cx(H2O)y for carbohydrates, x may begin at 3 in trioses and extend to many thousands in polysaccharides. The likely mistake is choosing 3 to 5 thousand by treating the range as a fixed upper limit rather than recognising that polysaccharides can contain many more sugar units.

1425. Keto group is represented as___________?

• A. CO
• B. C-COO-C
• C. HCOH
• D. HOH

Explanation: A keto group contains a carbonyl group within the carbon chain and is represented as C=O, commonly shortened in such options to CO. The likely mistake is HCOH, which resembles part of an aldehyde or hydroxyl-containing structure but does not represent a ketone carbonyl group.

1426. Animals obtain carbohydrates mainly from___________?

• A. Glucose
• B. Starch
• C. Sucrose
• D. Glycogen

Explanation: Starch is the main carbohydrate obtained by animals from plant-based foods such as cereals, potatoes and legumes; digestion breaks it down into glucose. Students may choose glucose because it is the final absorbable sugar, but animals usually obtain it after digesting starch rather than mainly eating free glucose.

1427. __________ is example of pure form of cellulose?

• A. Silk
• B. Wool
• C. Cotton
• D. Paper

Explanation: Cotton fibres are composed almost entirely of cellulose, a polymer of beta-glucose units, making cotton the usual example of relatively pure natural cellulose. Students may choose paper because it is also mainly cellulose, but paper commonly contains lignin, fillers or other additives and is not considered a pure form.

1428. The cell wall of oomycetes is chiefly composed of___________?

• A. Chitin
• B. Cellulose
• C. Lignin
• D. Proteins

Explanation: The cell walls of oomycetes are chiefly made of cellulose and other glucans, unlike true fungi, whose walls are mainly chitin. Students may choose chitin because oomycetes were historically called water moulds and treated as fungi, but their wall composition helps distinguish them from true fungi.

1429. The one which can tolerate highest external osmotic pressure is __________?

• A. Algae
• B. Amoeba
• C. Fungi
• D. Bacteria

Explanation: Fungi can grow in environments with high external osmotic pressure because their rigid cell walls and compatible-solute mechanisms help them retain water. Amoeba is a likely alternative, but freshwater amoeba is especially vulnerable to osmotic water entry and must expel water using a contractile vacuole.

1430. Which one is abundant in animals___________?

• A. Starch
• B. Glycogen
• C. Cellulose
• D. None of these

Explanation: Animals store excess glucose mainly as glycogen, a highly branched polysaccharide found especially in liver and skeletal muscles. Students may choose starch because it is the main storage carbohydrate of plants, whereas cellulose is a structural plant polysaccharide.