Basic Quiz – 19 October 2026 | Science & Tech

Correct Answer: (b) 1, 2 and 3 only

Explanation:

Statement 1 is correct: Mitochondria produce most of the ATP generated during aerobic cellular respiration through processes including oxidative phosphorylation. They are commonly called the powerhouse of the cell.

Statement 2 is correct: Ribosomes synthesise proteins by translating messenger RNA. They are present in both prokaryotic and eukaryotic organisms.

Statement 3 is correct: Lysosomes contain hydrolytic enzymes that digest damaged organelles, macromolecules and other cellular materials.

Statement 4 is incorrect: The Golgi apparatus modifies, sorts and packages proteins and lipids. In eukaryotic cells, hereditary information is primarily stored in nuclear DNA, with additional DNA in mitochondria and, in plants, chloroplasts.

Additional Information:

Mitochondria and chloroplasts contain their own DNA and ribosomes. This supports the endosymbiotic theory, which proposes that these organelles originated from ancient bacteria incorporated into ancestral eukaryotic cells.

Correct Answer: (c) 1, 2 and 3 only

Explanation:

Statement 1 is correct: Glass generally has different refractive indices for different wavelengths of visible light. Consequently, violet light is refracted more strongly than red light in an ordinary glass prism.

Statement 2 is correct: Total internal reflection occurs when light travels from a medium with a higher refractive index to one with a lower refractive index and the angle of incidence exceeds the critical angle.

Statement 3 is correct: Rayleigh scattering is stronger for shorter wavelengths. Blue light is scattered more effectively than red light by molecules in the atmosphere, contributing to the blue appearance of the sky.

Statement 4 is incorrect: Rainbow formation involves refraction, dispersion and internal reflection within water droplets, rather than reflection alone.

Additional Information:

Optical fibres work primarily on the principle of total internal reflection. They are widely used in telecommunications and medical endoscopy.

Correct Answer: (a) 1 and 2 only

Explanation:

Statement 1 is correct: At 25°C, a neutral aqueous solution has equal hydrogen-ion and hydroxide-ion activities, corresponding approximately to pH 7.

Statement 2 is correct: pH is logarithmic. A one-unit decrease corresponds to a tenfold increase in hydrogen-ion activity.

Statement 3 is incorrect: The difference between pH 3 and pH 5 is two units. Therefore, the hydrogen-ion activity is 100 times greater, not 10 times greater, at pH 3.

Statement 4 is incorrect: Although the familiar school-level pH scale is often presented as ranging from 0 to 14, strongly acidic or alkaline solutions can have pH values outside this range.

Additional Information:

Acid rain is conventionally defined as precipitation with a pH below approximately 5.6. Sulphur dioxide and nitrogen oxides contribute to acid rain through the formation of acids in the atmosphere.

Correct Answer: (c) 1, 2 and 3 only

Explanation:

Statement 1 is correct: A geostationary satellite must follow a circular, prograde orbit in Earth’s equatorial plane to remain above a fixed longitude.

Statement 2 is correct: Its orbital period matches Earth’s sidereal rotation period, approximately 23 hours, 56 minutes and 4 seconds.

Statement 3 is correct: Polar-orbiting satellites pass over or near the polar regions. Earth’s rotation allows successive orbital passes to observe different parts of the planet.

Statement 4 is incorrect: Geostationary satellites orbit above the equator, not the poles. Their viewing geometry makes them less suitable for high-latitude observations.

Additional Information:

India’s INSAT series has been used for telecommunications, broadcasting and meteorological services. Many Earth-observation satellites operate in Sun-synchronous orbits, allowing them to observe locations at approximately consistent local solar times.

Correct Answer: (d) 1, 2 and 3 only

Explanation:

Statement 1 is correct: CRISPR-Cas9 is a genome-editing technology that enables researchers to modify selected DNA sequences.

Statement 2 is correct: Guide RNA helps identify the target DNA sequence through complementary base pairing, subject to recognition requirements such as the presence of an appropriate PAM sequence.

Statement 3 is correct: Cas9 is a nuclease capable of cutting DNA at a targeted location.

Statement 4 is incorrect: CRISPR-Cas9 does not guarantee error-free editing. Off-target modifications and unintended changes at the target site remain important scientific and safety concerns.

Additional Information:

The 2020 Nobel Prize in Chemistry was awarded to Emmanuelle Charpentier and Jennifer Doudna for developing a method of genome editing using CRISPR-Cas9.

Genome editing has potential applications in treating genetic disorders, developing disease-resistant crops and biomedical research. However, human germline editing raises significant ethical and regulatory concerns.