The specific region where the exchange of gases occurs between air and blood in the lungs is the: MCQ with Answer and Explanation

The specific region where the exchange of gases occurs between air and blood in the lungs is the:
A. Alveoli
B. Bronchioles
C. Bronchi
D. Trachea
Answer: Option A
Solution (By JKSSB Mock Tests)
Alveoli are tiny, thin-walled air sacs surrounded by a network of pulmonary capillaries. Oxygen diffuses from alveolar air into blood, and CO₂ diffuses from blood into alveolar air. Bronchi and bronchioles are air passages, trachea is the windpipe. The large surface area of alveoli (about 70 m²) facilitates efficient gas exchange.

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Practice More Biology Questions

Question #1
The technique used to separate proteins based on their isoelectric point is:
A. SDS-PAGE
B. Isoelectric focusing
C. Western blotting
D. PCR

Correct Answer: Option B


Explanation:
Isoelectric focusing (IEF) separates proteins in a pH gradient according to their isoelectric point (pI), the pH at which a protein has no net charge and stops migrating. SDS-PAGE separates by size, Western blotting detects specific proteins after separation, PCR amplifies DNA. IEF is often used in 2D gel electrophoresis.

This question belongs to: Science Biology
Question #2
In a cross between a homozygous dominant plant (TT) and a heterozygous plant (Tt), what proportion of the offspring will show the recessive phenotype?
A. 100%
B. 25%
C. 50%
D. 0%

Correct Answer: Option D


Explanation:
Cross: TT × Tt. Gametes: T (from TT) and T or t (from Tt). Offspring genotypes: TT and Tt. Both express the dominant phenotype because the recessive allele t is masked by T. No tt offspring are produced, so 0% show the recessive trait.

This question belongs to: Science Biology
Question #3
Which enzyme catalyzes the primary carboxylation reaction in the Calvin cycle?
A. Nitrogenase
B. PEP carboxylase
C. RuBisCO
D. Carbonic anhydrase

Correct Answer: Option C


Explanation:
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.

This question belongs to: Science Biology