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Vision and Chemistry By: Robin E. Renzi

Vision and Chemistry By: Robin E. Renzi. Vision is often considered our most important sense of the five senses. But what is responsible for our ability to see? . Rhodopsin is the protein vital to the process of sight.

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Vision and Chemistry By: Robin E. Renzi

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  1. Vision and ChemistryBy: Robin E. Renzi

  2. Vision is often considered our most important sense of the five senses. But what is responsible for our ability to see? Rhodopsin is the protein vital to the process of sight. When a light photon is absorbed by our eyes an impulse is sent down the optic nerve to the vertebrate photoreceptor protein reacting with the double bonds in the retinal portion of the rhodopsin protein located at carbon atoms 11 and 12 causing a cis-trans transition. At this covalent bond the 11-cis carbon isomerizes after proton absorption to form an all-trans geometry shape. Rhodopsin

  3. The Rhodopsin Cycle in Words • Opsin does not absorb visible light, but when it is bonded with 11-cis-retinal to form rhodopsin, the new molecule then has a very broad absorption band in the visible region of the spectrum. The peak of the absorption is around 500 nm, which matches the output of the sun closely. • When a photon of light falls onto rhodopsin, the molecule absorbs the energy and the cis-double-bond between C-11 and C-12 in the retinal is temporarily converted into a single bond. This means the molecule can now rotate around this bond, which it does by swiveling at 180°. The double bond then reforms and locks the molecule back into position in a trans configuration. • At this point the light has isomerised the molecule from cis to trans, changing the shape of the retinal from curved to straight. The energy in the light photon has been converted into atomic motion.

  4. The Rhodopsin Cycle in Words • The 11-cis-retinal fits into the Opsin binding site perfectly, however all-trans-retinal is the wrong shape. The Schiff base linkage becomes unstable, and the molecule undergoes a series of shape changes to try and better fit the binding site, before eventually breaking free of the Opsin altogether. • The rapid movements of the retinal are transferred to the protein, and from there goes into the phospholipid membrane and nerve cells to which it is attached. This generates nerve impulses which travel along the optic nerve to the brain, and we perceive these impulses as visual signals, or what we call - sight. • The free all-trans-retinal is then converted back into the cis form by a series of enzyme-catalyzed reactions, where it is reattaches to another Opsin ready for the next light photon to begin the process again.

  5. The Rhodopsin Cycle with Attributing Enzymes

  6. 1)http://education.vetmed.vt.edu/Curriculum/VM8054/EYE/RHODOPSN.HTM1)http://education.vetmed.vt.edu/Curriculum/VM8054/EYE/RHODOPSN.HTM 2)http://images.google.com/imgres?imgurl=http://www.du-counseling.info/uploads/images/Articles_images/eyes.jpg&imgrefurl=http://www.du-counseling.info/news/32/51/Assess-people-by-eyes-color.html&usg=__fppMoWQQ4sympqwGve8Y6iwnKEk=&h=400&w=365&sz=32&hl=en&start=61&um=1&itbs=1&tbnid=f3GbV4sh22C1ZM:&tbnh=124&tbnw=113&prev=/images%3Fq%3Deyes%26ndsp%3D21%26hl%3Den%26rlz%3D1T4TSNA_enUS359US359%26sa%3DN%26start%3D42%26um%3D1 Works Cited 3)http://images.google.com/imgres?imgurl=http://cas.bellarmine.edu/tietjen/HumanBioogy/Sensory/Rhodopsin.gif&imgrefurl=http://cas.bellarmine.edu/tietjen/HumanBioogy/sensory_systems.htm&usg=__0x3liRvK0TfjRAzV9tvGsZWCUlU=&h=475&w=635&sz=35&hl=en&start=2&um=1&itbs=1&tbnid=NUh6ca1G9H8XAM:&tbnh=102&tbnw=137&prev=/images%3Fq%3Drhodopsin%26ndsp%3D21%26hl%3Den%26rlz%3D1T4TSNA_enUS359US359%26sa%3DG%26um%3D1 4)http://images.google.com/imgres?imgurl=http://kugi.kribb.re.kr/KUGI/Pathways/BioCarta/h_rhodopsinPathway/h_rhodopsinPathway.gif&imgrefurl=http://kugi.kribb.re.kr/KUGI/Pathways/BioCarta/h_rhodopsinPathway/&usg=__cGg4L5UjT4pgKOKZQ1Q-q06a6Tk=&h=515&w=600&sz=47&hl=en&start=13&um=1&itbs=1&tbnid=D4UYbsG6cxukSM:&tbnh=116&tbnw=135&prev=/images%3Fq%3Drhodopsin%26hl%3Den%26rlz%3D1T4TSNA_enUS359US359%26sa%3DG%26um%3D1

  7. 5)http://images.google.com/imgres?imgurl=http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/9925.jpg&imgrefurl=http://www.nlm.nih.gov/medlineplus/ency/imagepages/9925.htm&usg=__aWRlkoTjgzqTgN_g5Gnbxy8OmUE=&h=320&w=400&sz=11&hl=en&start=41&um=1&itbs=1&tbnid=v3J41b3YHFVnKM:&tbnh=99&tbnw=124&prev=/images%3Fq%3Dvision%26start%3D21%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1T4TSNA_enUS359US359%26ndsp%3D21%26tbs%3Disch:15)http://images.google.com/imgres?imgurl=http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/9925.jpg&imgrefurl=http://www.nlm.nih.gov/medlineplus/ency/imagepages/9925.htm&usg=__aWRlkoTjgzqTgN_g5Gnbxy8OmUE=&h=320&w=400&sz=11&hl=en&start=41&um=1&itbs=1&tbnid=v3J41b3YHFVnKM:&tbnh=99&tbnw=124&prev=/images%3Fq%3Dvision%26start%3D21%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1T4TSNA_enUS359US359%26ndsp%3D21%26tbs%3Disch:1 Works Cited

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