Which enzyme catalyzes the primary carboxylation reaction in the Calvin cycle? MCQ with Answer and Explanation

Which enzyme catalyzes the primary carboxylation reaction in the Calvin cycle?
A. Nitrogenase
B. PEP carboxylase
C. Carbonic anhydrase
D. RuBisCO
Answer: Option D
Solution (By JKExamLibrary)
RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the most abundant protein on Earth and the key enzyme in the Calvin cycle (C3 pathway). It catalyzes the fixation of CO2 by attaching it to Ribulose-1,5-bisphosphate (RuBP) to form a 6-carbon intermediate that immediately splits into two molecules of 3-PGA.

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Practice More Biology Questions

Question #1
The cell wall of bacteria is primarily composed of:
A. Chitin
B. Silica
C. Peptidoglycan (Murein)
D. Cellulose

Correct Answer: Option C


Explanation:
The bacterial cell wall is a rigid structure that provides shape and protection. It is primarily composed of peptidoglycan (also known as murein), a polymer consisting of sugars and amino acids. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane. Cellulose is in plant walls, and chitin is in fungal walls.

This question belongs to: Science Biology
Question #2
Consider statements about microorganisms: 1. Bacteria are prokaryotic organisms. 2. Fungi are eukaryotic organisms. 3. Viruses have a cellular structure. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 2 only
D. 1 and 3 only

Correct Answer: Option C


Explanation:
Bacteria are unicellular prokaryotic organisms, characterized by the absence of a true nucleus and membrane-bound organelles. Fungi are eukaryotic organisms, possessing a true nucleus and membrane-bound organelles, and can be unicellular (yeasts) or multicellular (molds, mushrooms). Viruses are acellular, non-cellular entities; they consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid) and lack any cellular structure or metabolic machinery. Thus, statements 1 and 2 are correct.

This question belongs to: Science Biology
Question #3
In genetics, the 'Hardy-Weinberg equilibrium' can be disrupted by several evolutionary forces. Which of the following is NOT a factor that disrupts this equilibrium?
A. Mutation
B. Gene flow (migration)
C. Random mating
D. Genetic drift

Correct Answer: Option C


Explanation:
The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant (in equilibrium) from generation to generation in the absence of evolutionary influences. The conditions required for this equilibrium are: no mutation, random mating, no gene flow (migration), very large population size (no genetic drift), and no natural selection. Therefore, random mating is a condition that MAINTAINS the equilibrium, not a factor that disrupts it. Non-random mating would disrupt it.

This question belongs to: Science Biology