Retinal

Retinal is a form of vitamin A that plays a crucial role in the biological process of vision. It is one of the many forms of vitamin A, which also include retinol and retinoic acid. Retinal is an essential component of the rhodopsin and iodopsin molecules in the retina of the eye, which are responsible for converting light into electrical signals that can be interpreted by the brain.

Structure and Function

Retinal is a polyene chromophore, and is the basis of animal vision. It undergoes a series of transformations when it absorbs light, changing its shape in a process called photoisomerization. This change in shape triggers a series of events that result in an electrical signal being sent to the brain.

Retinal is also involved in the production of rhodopsin, a pigment found in the rods of the retina that is responsible for the first stage of light detection. It is also a component of iodopsin, a pigment found in the cones of the retina that is responsible for color vision.

Synthesis and Metabolism

Retinal is synthesized from beta-carotene, a type of carotenoid that is found in many fruits and vegetables. The body converts beta-carotene into retinal through a series of enzymatic reactions.

Once synthesized, retinal can be converted into other forms of vitamin A, such as retinol and retinoic acid. These forms of vitamin A have different functions in the body, with retinol being important for growth and development, and retinoic acid being important for cell differentiation.

Clinical Significance

Deficiency in retinal can lead to night blindness, as the body is unable to produce enough rhodopsin to detect light in low-light conditions. Prolonged deficiency can also lead to xerophthalmia, a condition characterized by dry eyes and damage to the cornea.

Overconsumption of retinal can lead to hypervitaminosis A, a condition characterized by nausea, irritability, anorexia, vomiting, blurry vision, headaches, hair loss, muscle pain, and skin peeling.

See Also

• Vitamin A
• Rhodopsin
• Iodopsin
• Retinol
• Retinoic acid

References

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  Retinal Isomers

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  Rhodopsin and Transducin

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  Visual Cycle