The pigment that gives blue-green algae their color is: MCQ with Answer and Explanation

Explanation:
Blood group O lacks A and B antigens on red cells but contains both anti-A and anti-B antibodies in plasma. This makes it the universal donor for packed red cells but dangerous plasma donor. Group AB has no antibodies. So, the presence of both antibodies is correct.

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:
Mature mammalian red blood cells (erythrocytes) lose their nucleus and other organelles during development to maximize space for hemoglobin. Thus they are anucleate. They cannot divide or repair themselves and have a lifespan of about 120 days. Neurons, leukocytes, and hepatocytes are nucleated. RBCs obtain energy through anaerobic glycolysis.