41.Which of the following is/are true of enzymes ?1. Proteinaceous in nature2. Specific in nature3. Converted in chemical reactions 4. Act on the substrate at any temperature

42.Which of the following statements is/are true of white blood corpuscles ?1. They are irregular structures2. They are nucleated3. They are manufactured in the lymph and spleen4. They live for about four months

43.Which of the following is a physical basis of life ?

44.The oral polio vaccine was discovered by :

45.Which of the following structures are commonly present in animal cells and not in plant cells ? 1. Mitochondria2. Lysosomes3. Ribosomes4. Centrosomes