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Slide 3 : Vision is such an everyday occurrence that we seldom stop to think and wonder how we are able to see the objects that surround us. Yet the vision process is a fascinating example of how light can produce molecular changes. In mammals the organ that is responsible for vision is the eye. Light enters the eye and it is then focused on the retina by the lens.
The retina is a layer of cells that cover the interior surface of the eye. The retina contains molecules that undergo a chemical change upon absorbing light, but it is the brain that actually makes sense of the visual information to create an image.
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Rods and cones contain similar chemicals to allow them to operate. in the top of each cell, There is a chemical called rhodopsin, a light sensitive substance formed from a protein called opsin and which is bonded to a pigment called 11-cis retinal. 11-cis retinal is synthesized in the liver from dietary vitamin a, and it is the key substance. : Rods and cones contain similar chemicals to allow them to operate. in the top of each cell, There is a chemical called rhodopsin, a light sensitive substance formed from a protein called opsin and which is bonded to a pigment called 11-cis retinal. 11-cis retinal is synthesized in the liver from dietary vitamin a, and it is the key substance.
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Photochemistry of vision : Photochemistry of vision When light is absorbed by rhodopsin, the double bond electrons are promoted to a p* orbital, which allows the bond to free rotate and the molecule, is converted into trans-retinal. The trans-retinal is bleached and cannot respond to more light until it isomerzies back to the cis- form and attaches to the protein opsin again.
Slide 11 : Once a cell has been stimulated, the molecules have to return to their original form. The opsin reattaches itself to the retinal and reforms the double bond to remake the rhodopsin molecule. The temporary blindness that occurs when looking at bright light is caused by cell overload and rhodopsin breakdown. As the molecules slowly return to their natural form and some are then disassociated, vision returns.
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Slide 15 : Is a Red rose red in the dark?
How color is registered within the eye is a very important factor in the perception of light interaction with matter. In the human eye light is registered on the retina, a thin film of tissue which covers the interior of the eye behind the lens.
Slide 16 : The retina contains photosensitive cells known as rods and cones. Rod cells are used in dim light, and produce only black and white images. Cone cells operate in bright light and produce the colors we perceive
The answer must be no - Since what we see as color must be light which is reflected off the object. In darkness this cannot happen. : The answer must be no - Since what we see as color must be light which is reflected off the object. In darkness this cannot happen. Is a red rose red in the dark?