Consider statements about cell biology: 1. The plasma membrane is selectively permeable. 2. The nucleolus is the site of protein synthesis. 3. Lysosomes contain digestive enzymes. Which are correct? MCQ with Answer and Explanation

Explanation:
In the apoplast pathway, water moves through cell walls and intercellular spaces without crossing membranes. However, at the endodermis, the Casparian strip (suberin deposition) blocks apoplastic movement, forcing water to enter the symplast (via plasma membrane). Thus, apoplastic movement stops at the endodermis. This ensures selective uptake of minerals.

Explanation:
Eutrophication is the excessive enrichment of water bodies with nutrients (primarily nitrates and phosphates from fertilizers and sewage). This leads to rapid growth of algae, known as an algal bloom. When the algae die, their decomposition by bacteria consumes large amounts of dissolved oxygen, leading to hypoxia (low oxygen levels) or anoxia, causing the death of fish and other aquatic organisms.

Explanation:
Iodine is a key constituent of the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃). Deficiency leads to goiter and hypothyroidism. Iron is for hemoglobin, calcium for bones, zinc for enzyme function. Iodized salt is a public health measure to ensure adequate iodine intake.