Consider statements about environment: 1. Carbon dioxide is a greenhouse gas. 2. Methane is a greenhouse gas. 3. Oxygen is a major greenhouse gas. Which are correct? MCQ with Answer and Explanation
Consider statements about environment: 1. Carbon dioxide is a greenhouse gas. 2. Methane is a greenhouse gas. 3. Oxygen is a major greenhouse gas. Which are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3
Answer: Option B
Solution (By JKSSB Mock Tests)
Greenhouse gases trap heat in the Earth's atmosphere, contributing to the greenhouse effect and global warming. Carbon dioxide (CO2) and methane (CH4) are potent greenhouse gases emitted through human activities like fossil fuel combustion and agriculture. Oxygen (O2) and nitrogen (N2), which make up the majority of the atmosphere, are not greenhouse gases as they do not absorb infrared radiation. Thus, statements 1 and 2 are correct.
Explanation:
HIV specifically infects and destroys CD4+ T cells, leading to immunodeficiency and AIDS. Without treatment, opportunistic infections occur.
Explanation:
Differential centrifugation separates organelles by size and density by spinning homogenized cells at progressively higher speeds. Each pellet is enriched in a particular organelle. Density gradient centrifugation further refines separation. Electrophoresis separates by charge/size, chromatography by differential partitioning, spectrophotometry measures absorbance.
Explanation:
Eukaryotic ribosomes are 80S and composed of a small 40S subunit and a large 60S subunit. Prokaryotic ribosomes are 70S with 30S and 50S subunits. The S (Svedberg) value is a measure of sedimentation rate, not simply additive. Both ribosome types synthesize proteins, but the structural difference allows selective antibiotic targeting (e.g., streptomycin acts on 70S).
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