The fluid that lubricates joints and reduces friction is: MCQ with Answer and Explanation

Explanation:
Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, enabling the transport of water, ions, molecules, and even some viruses between them, thus ensuring cytoplasmic continuity. Gap junctions perform a similar function in animal cells, while tight junctions and desmosomes are for sealing and adhesion, respectively.

Explanation:
Photorespiration is a wasteful pathway that occurs when RuBisCO fixes O2 instead of CO2, producing phosphoglycolate. This 2-carbon compound is metabolized through a complex pathway involving three organelles: it is processed in the peroxisome, then the mitochondria, and finally returns to the chloroplast. This process consumes ATP and releases CO2 without producing any sugar.

Explanation:
Iron (Fe²⁺) is at the center of the heme group in hemoglobin, enabling reversible oxygen binding. Calcium is in bones, magnesium in chlorophyll, zinc in many enzymes. Iron deficiency leads to anemia.