Five tricky JEE/NEET-level questions on Breathing And Exchange Of Gases with traps explained and worked solutions.

Breathing And Exchange Of Gases: Tricky Problems from JEE/NEET

These are the sort of questions that catch even well-prepared students off guard. They’re not impossibly hard — they’re just phrased carefully enough that a quick reading gives the wrong answer. We’ll work through five of them together on pulmonary ventilation, gas exchange, oxygen dissociation curve, and transport of CO₂.

Tricky Problem 1 — The Reversed Option

Question. All of the following are TRUE about tidal volume in Breathing And Exchange Of Gases EXCEPT:

a) It occurs in all eukaryotic cells. b) It is regulated by enzyme activity. c) It never occurs in prokaryotes. d) It plays a role in energy metabolism.

The trap: the word “EXCEPT”. Students in a rush mark the first true statement they see.

Underline “EXCEPT” with your pen. Physically mark it.

Option (c) uses the absolute word “never” — in biology, “never” is usually wrong.

Answer: (c). Prokaryotes do have this feature in a modified form. NEET loves absolute words — “always”, “never”, “only” — as distractor flags.

Tricky Problem 2 — The Double Negative

Question. It is NOT correct to say that residual volume is NOT involved in regulation of Breathing And Exchange Of Gases. Which statement best captures the intent?

“Not correct to say it is not involved” → it IS involved.

Look for the option that simply states involvement without qualifiers.

The intent is: “residual volume is involved in regulation of Breathing And Exchange Of Gases.” Always rewrite double-negative questions in your rough sheet before answering.

Tricky Problem 3 — The Numbers Trap

Question. If Bohr effect doubles its concentration and the reaction it controls follows first-order kinetics, by what factor does the rate change?

Rate $\propto$ [substrate] $^1$ . Doubling substrate doubles the rate.

Many students see “doubles” and pick 4× (second-order assumption). Read the kinetic order carefully.

Answer: Rate doubles (2×). First-order means linear dependence on concentration.

Tricky Problem 4 — The “Best” Option

Question. Which is the BEST description of chloride shift in Breathing And Exchange Of Gases?

a) A structural component. b) A regulatory molecule. c) A structural component that also regulates activity. d) A molecule found in all living cells.

“BEST” questions usually reward the most complete option, not the simplest. In this case, (c) captures more truth than (a) or (b) alone.

Answer: (c). Option (d) is true but non-specific; (a) and (b) are subsets of (c). The most complete correct option wins.

Tricky Problem 5 — The Multi-Step Calculation

Question. A cell enters mitosis with $2n = 46$ . After two successive mitotic divisions, how many cells exist and what is the chromosome number in each?

1 cell → 2 cells, each $2n = 46$ .

2 cells → 4 cells, each $2n = 46$ .

Mitosis is equational. Chromosome number per cell stays the same, only cell count doubles each round.

Answer: 4 cells, each with $2n = 46$ chromosomes. The trap is assuming chromosome halving (which happens in meiosis, not mitosis).

The Meta-Lesson

Tricky problems reward three habits:

Slow reading. Speed-reading kills tricky questions. Read the stem twice.
Pen-marking key words. “EXCEPT”, “NOT”, “BEST”, “ONLY” should always get a physical mark from your pen.
Option elimination. Absolute words like “never” and “always” are usually wrong in biology.

Build these habits during mock tests and tricky questions stop feeling tricky.

Quick Recap

Watch for “EXCEPT” and negative stems.
Unwrap double negatives on rough paper.
Check kinetic order before doubling rates.
“BEST” option = most complete option.
Mitosis vs meiosis: don’t halve chromosomes in mitosis.

Master these five patterns and you’ve locked in the pulmonary ventilation, gas exchange, oxygen dissociation curve, and transport of CO₂ questions the paper-setters designed specifically to trip you up.