All Free Biology MCQs with Answers

1691. Which chemical component has the same % in bacterial as well as the mammalian cell_____________?

• A. Water
• B. Carbohydrate
• C. Proteins
• D. Lipids

Explanation: Water forms approximately 70% of the mass of both typical bacterial and mammalian cells, although the exact percentage varies with cell type and conditions. Proteins, carbohydrates and lipids differ more markedly in their relative proportions between these cells. Students may choose proteins because they are major cell components, but their percentage is not generally the same in bacteria and mammals.

1692. Which one is the basic element of organic compounds _________________?

• A. Oxygen
• B. Hydrogen
• C. Sulphur
• D. Carbon

Explanation: Carbon is the basic element of organic compounds because its four covalent bonds allow it to form stable, diverse molecular skeletons. It combines with hydrogen, oxygen, nitrogen and other elements to produce carbohydrates, lipids, proteins and nucleic acids. The likely mistake is choosing hydrogen or oxygen because they are also common in organic molecules, but they do not provide the main framework.

1693. The bond formed when two or more atoms complete their electron shells by sharing electrons is called_____________?

• A. Ionic bond
• B. Hydrogen bond
• C. Covalent bond
• D. Electrovalent bond

Explanation: A covalent bond forms when atoms share one or more pairs of electrons to complete or stabilize their outer electron shells. Ionic or electrovalent bonds form through transfer of electrons and subsequent attraction between ions, not sharing. Students may choose ionic bond because both bond types help atoms achieve stable electron arrangements, but their mechanisms differ.

1694. Chlorophyll is a/an _____ molecule?

• A. Inorganic
• B. Cationic
• C. Anionic
• D. Organic

Explanation: Chlorophyll is an organic molecule because it is a carbon-based pigment with a complex ring structure and a magnesium ion at its centre. The likely mistake is choosing inorganic because chlorophyll contains magnesium, but the presence of one metal ion does not make the entire carbon-based molecule inorganic.

1695. Breakdown of large molecules into smaller ones utilizing water molecules is_________?

• A. Hydration
• B. Hydrolysis
• C. Dehydration synthesis
• D. Electrolysis

Explanation: Hydrolysis uses water to break a covalent bond in a large molecule, such as splitting a polymer into smaller units. Students may choose dehydration synthesis because it also involves water, but dehydration synthesis removes water to join smaller molecules instead of using water for breakdown.

1696. Branch of biology which deals with the study of chemical components and chemical processes in living organisms is called________________?

• A. Molecular biology
• B. Physiology
• C. Biochemistry
• D. Atomic biology

Explanation: Biochemistry studies the chemical substances present in living organisms and the reactions they undergo, including metabolism and enzyme action. Molecular biology mainly focuses on molecules such as DNA and RNA in relation to cellular processes, so it is the likely alternative misunderstanding.

1697. Which one is a micromolecule__________?

• A. Polysaccharide
• B. Protein
• C. Hemoglobin
• D. ATP

Explanation: ATP is a micromolecule because it is a relatively small molecule made of adenine, ribose and phosphate groups, although it transfers chemical energy in cells. Protein, hemoglobin and polysaccharide are macromolecules, so students may choose protein because it is also a major biological molecule.

1698. The one which is present in all living things

• A. Cell nucleus
• B. DNA or RNA
• C. Cell membrane
• D. Vacuole

Explanation: All cellular living organisms contain genetic material, with DNA serving as the hereditary material and RNA functioning in gene expression; the phrase DNA or RNA also covers the genetic-material distinction used for biological systems. Students may choose cell membrane because cells require a boundary, but the wording includes all living things and does not state that every living structure must have a membrane as its defining common feature.

1699. Communities are ________ collection of organisms?

• A. Static
• B. Dynamic
• C. May be static or dynamic
• D. None of these

Explanation: A community is a collection of populations living together and interacting in an area, and its species composition and population sizes change with time. Therefore, communities are dynamic rather than static. Students may choose “may be static or dynamic” because they mistake a temporary lack of visible change for true ecological stability.

1700. Which one is not correct for a productive theory?

• A. It is predictive
• B. It has explanatory power
• C. It discourages suggestion of different hypotheses
• D. None of these

Explanation: A productive scientific theory makes predictions, explains observations and stimulates new questions and hypotheses for testing. Therefore, it should not discourage different hypotheses; students may choose “none of these” if they overlook that option c directly contradicts the creative and testable nature of scientific theories.