Identify the correct statement about respiration: MCQ with Answer and Explanation

Explanation:
Glucagon, secreted by alpha cells of the pancreas when blood glucose is low, binds to liver receptors activating glycogenolysis (glycogen → glucose) and gluconeogenesis. Insulin promotes glycogenesis (glucose → glycogen). Thyroxine affects metabolism, somatostatin inhibits both insulin and glucagon.

Explanation:
The Casparian strip is a band of cell wall material that runs radially and transversely through the cell walls of the endodermal cells in plant roots, but is absent from the tangential walls. It is primarily composed of suberin (a waxy, waterproof substance) and lignin (a complex polymer). This strip acts as a physical and chemical barrier, blocking the passive, apoplastic flow of water and dissolved minerals between the cells. It forces these substances to cross the selectively permeable plasma membrane and enter the symplastic pathway, allowing the plant to control what enters the vascular cylinder.

Explanation:
HIV is a retrovirus with two copies of single-stranded RNA as its genome. It uses reverse transcriptase to convert RNA into DNA upon infection. Double-stranded DNA is typical of many organisms. Single-stranded DNA viruses exist (e.g., parvovirus). Double-stranded RNA viruses include rotavirus. The viral RNA genome enables integration into host DNA via a DNA intermediate.