Vitamin A Functions and Retinoid Cycle

The video explores vitamin A, its structure, metabolism, and function in the human body, starting with carotenoids in plants. It discusses how carotenoids like beta carotene are converted to vitamin A, their structural features, and their role in photoprotection. The conversion pathway of carotenoids to retinal and the retinoid cycle's significance in vision are also covered.

What is the primary role of carotenoids in plants?

• To produce oxygen

• To store nutrients

• To absorb excess UV radiation

• To provide energy for growth

Which carotenoid has the highest vitamin A activity?

• Alpha carotene

• Gamma carotene

• Beta cryptoxanthin

• Beta carotene

What structural feature is crucial for a carotenoid to have vitamin A activity?

• Presence of a hydroxyl group

• A specific ring structure

• Multiple double bonds

• A long carbon chain

What enzyme is responsible for splitting beta carotene in the human body?

• Esterification enzyme

• Rhodopsin

• Retinal dehydrogenase

• Carotenoid monooxygenase

What is the initial form of retinal that is functional in the visual cycle?

• All trans retinal

• 11 CIS retinal

• Retinoic acid

• Retinyl ester

In the retinoid cycle, what happens to 11 CIS retinal after it is used?

• It is stored as retinyl ester

• It is recycled back to 11 CIS retinal

• It is converted to retinoic acid

• It is excreted from the body

What role does retinal play in the human eye?

• It acts as a cofactor for rhodopsin

• It provides energy for the eye

• It stores vitamin A

• It protects the eye from UV light