Receptor sites for neurotransmitters are present on

Myelin sheath is produced by

Good vishion depends on adequate intake of carotene rich food.

Select the best option from the following statements.
(1)  Vitamins A derivatives are formed from carotene,
(2)  The photopigments are embedded in the membrane discs of the inner segment.
(3)  Retinal is a derivative of vitamin A.
(4)  Retinal is a light absorbing part of all the visual photopigments.

Choose the correct statement.