Key Concepts & Formulas

10 Practice MCQs

Q1. Which organelle is known as the “powerhouse of the cell”? A) Nucleus B) Mitochondria C) Ribosome D) Golgi body

Answer: B) Mitochondria

Solution: Mitochondria produce ATP (adenosine triphosphate) which is the energy currency of the cell. They have their own DNA and can replicate independently.

Shortcut: “M” in Mitochondria = “M” in Might/Power

Concept: Biology Basics - Cell organelles and their functions

Q2. What is the pH of human blood? A) 6.8 B) 7.0 C) 7.4 D) 8.0

Answer: C) 7.4

Solution: Human blood is slightly alkaline with a pH range of 7.35-7.45. Below 7.35 is acidosis, above 7.45 is alkalosis.

Shortcut: Remember “7.4” as “74” - average human lifespan in developed countries

Concept: Biology Basics - Human physiology

Q3. Which vitamin is produced in the human body when exposed to sunlight? A) Vitamin A B) Vitamin B C) Vitamin C D) Vitamin D

Answer: D) Vitamin D

Solution: Vitamin D is synthesized in the skin when exposed to UV-B radiation from sunlight (7-dehydrocholesterol → Vitamin D3).

Shortcut: “D” for “Daylight”

Concept: Biology Basics - Vitamins and their sources

Q4. A train driver working night shifts for 3 months develops fatigue and bone pain. Which hormone deficiency is most likely? A) Insulin B) Thyroxine C) Melatonin D) Calcitonin

Answer: C) Melatonin (leading to Vitamin D deficiency)

Solution: Night shift workers have disrupted circadian rhythms → reduced melatonin → less sun exposure → Vitamin D deficiency → bone pain and fatigue.

Shortcut: Night shift = No sun = Vitamin D problem

Concept: Biology Basics - Hormones and lifestyle diseases

Q5. In the railway canteen, food left at room temperature for 4 hours causes bacterial growth. If bacteria double every 20 minutes, how many times has the population increased? A) 8 times B) 12 times C) 16 times D) 24 times

Answer: B) 12 times

Solution: 4 hours = 240 minutes. Doubling every 20 minutes → 240/20 = 12 doubling periods → 2¹² = 4096 times increase.

Shortcut: Hours × 3 = doubling periods (for 20-minute cycles)

Concept: Biology Basics - Bacterial growth and reproduction

Q6. A station cooler uses water from a borewell with pH 5.5. What type of water is this and which fish can survive? A) Neutral - all fish B) Acidic - only tolerant species C) Alkaline - no fish D) Normal - freshwater fish

Answer: B) Acidic - only tolerant species

Solution: pH 5.5 is acidic (below 7). Most freshwater fish need pH 6.5-8.5. Only acid-tolerant species like some minnows can survive.

Shortcut: Below 7 = Acidic (think “acid rain” pH 5-6)

Concept: Biology Basics - pH and aquatic life

Q7. Railway workers in different departments show varying lung capacities. Arrange these from highest to lowest: Track workers, Office staff, Loco pilots, Ticket checkers. A) Track > Loco > Ticket > Office B) Loco > Track > Ticket > Office C) Office > Ticket > Loco > Track D) Track > Office > Ticket > Loco

Answer: B) Loco > Track > Ticket > Office

Solution: Loco pilots need maximum oxygen for concentration → highest lung capacity. Track workers have physical labor but less mental stress. Office staff have sedentary lifestyle → lowest capacity.

Shortcut: “LOCOMOTIVE” needs most “OXYMOTIVE”

Concept: Biology Basics - Respiratory system and occupation

Q8. A 1500m long tunnel reduces oxygen levels by 15%. If normal air has 21% O₂, what percentage do train passengers breathe, and what compensatory mechanism activates? A) 17.85%, hyperventilation B) 18.5%, increased heart rate C) 17.85%, increased RBC production D) 18.5%, Bohr effect

Answer: A) 17.85%, hyperventilation

Solution: 21% × 0.85 = 17.85%. Low O₂ triggers immediate hyperventilation (increased breathing rate) for quick compensation.

Shortcut: 21% - (21% × 0.15) = 21 - 3.15 = 17.85%

Concept: Biology Basics - Respiratory adaptations

Q9. Railway hospital blood bank has 100 units: 30% A+, 25% O+, 20% B+, 15% AB+, 10% others. Emergency needs 8 units for B- patients. If B- is 2% of population, how many units expected available? A) 2 B) 3 C) 4 D) 5

Answer: A) 2

Solution: B- is 2% of population → 2% of 100 = 2 units expected. Rh- is less common than Rh+.

Shortcut: Percentage directly equals units in 100 unit stock

Concept: Biology Basics - Blood group distribution

Q10. Track temperature reaches 65°C in summer. If an enzyme’s optimal temperature is 37°C and it denatures at 60°C, by what factor does its activity decrease if Q₁₀ = 2 for every 10°C rise? A) 4 B) 8 C) 16 D) 32

Answer: C) 16

Solution: From 37°C to 65°C = 28°C rise. Q₁₀ = 2 means doubling every 10°C. 28°C ≈ 3 doubling periods → 2³ = 8 times increase, but above 60°C enzyme denatures → activity drops to near zero.

Shortcut: Above denaturation temp → activity = 0 (regardless of Q₁₀)

Concept: Biology Basics - Enzyme kinetics and temperature

5 Previous Year Questions

PYQ 1. Which part of the human brain controls body balance? [RRB NTPC 2021 CBT-1]

Answer: Cerebellum

Solution: Cerebellum (meaning “little brain”) coordinates voluntary movements, balance, and posture. It’s located at the back of the brain under the cerebrum.

Exam Tip: Remember “Cerebellum = Coordination & Balance”

PYQ 2. What is the normal blood pressure of a healthy human adult? [RRB Group D 2022]

Answer: 120/80 mmHg

Solution: 120 mmHg (systolic - heart contracts) / 80 mmHg (diastolic - heart relaxes). Above 140/90 is hypertension.

Exam Tip: Remember “120/80” as “12/8” like clock numbers

PYQ 3. Which gas is released during photosynthesis? [RRB ALP 2018]

Answer: Oxygen (O₂)

Solution: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂. Oxygen comes from water molecules, not CO₂.

Exam Tip: Photosynthesis releases O₂, respiration consumes O₂

PYQ 4. How many chambers are there in a human heart? [RRB JE 2019]

Answer: 4 chambers (2 atria + 2 ventricles)

Solution: Right atrium → Right ventricle → Lungs → Left atrium → Left ventricle → Body. Double circulation system.

Exam Tip: Remember “4” like 4 valves, 4 chambers

PYQ 5. Which vitamin deficiency causes night blindness? [RPF SI 2019]

Answer: Vitamin A

Solution: Vitamin A forms retinal, needed for rhodopsin (night vision pigment) in rod cells. Found in carrots, green vegetables.

Exam Tip: “A” for “Aye-aye” (eye-eye) night vision

Speed Tricks & Shortcuts

Common Mistakes to Avoid

Quick Revision Flashcards

Topic Connections

How Biology Basics connects to other RRB exam topics:

• Direct Link: Physics - Osmosis and diffusion in railway water systems
• Combined Questions: Chemistry - pH testing of railway water supplies, Biology - acid rain effects on tracks
• Foundation For: Advanced physiology for medical standards in railway jobs, Environmental science for eco-friendly practices