The Relationship between Human Eyes and Camera Lenses

1. The Relationship between Human Eyes and Camera Lenses IB Chemistry SL Ellin Ueno

2. The Overview of Biochemical Path Way involved in Retina • Three primary cells in retina are called rod cell, transducin, and phosphodiesterase. • In rod cell, there is a pigmentary cell called rhodopsin. • Transducin is a type of G protein. • Phosphodiesterase is an enzyme. • Rhodopsin is composed of opsin (the protein) and 11-cis-retinal (vitamin A).

3. The Overview of Biochemical Path Way involved in RetinaRhodopsin • The figure on the left demonstrates the position of 11-cis retinal within Rhodopsin. • composed of opsin (the protein) and 11-cis-retinal (vitamin A). • After it absorbs light (photon) in the visible range, 11-cis-retinal changes its structure and forms all-trans-retinal. • All-trans-retinal is a straight chain molecule. http://www.chm.bris.ac.uk/webprojects2003/rogers/998/rhohum.jpg

4. The Overview of Biochemical Path Way involved in RetinaTransformation of 11cis-retinal • 11-cis-retinal separates itself from opsin and activates transducin. • As opsin is released, phosphodiesterase is activated. • This reduces the amount of production of cGMP. • This closes the Na (sodium) channel and evokes overshoot. • Overshoot can be identified as sending information signals to the human brain. • The brain then recognizes the signal and visualize what we "see."

5. The Overview of similarities and differences between human eye and camera lensSummary Similarities: • Both human eye and camera lens capture photons from light. • Both focus photons into one point, focal point. • Both allows an element to react with photons. • Images transferred are flipped (up-side down). Differences: • Human eye allows photons to react with with chemicals inside the retina; rod cell absorbs photon and11-cis-retinal changing its structure. • Human brain recognizes the image. • Camera lens allows photons to react with with silver halide on a film to visualize the image. • Film displays the image. • There is no complexity or biochemistry involved in its operation.

6. Design Variables Independent Variable: wavelengths of the light Dependent Variable: the boiling point of the product Controlled Variables: the distance between the light source and the beaker that contains 11-cis-retinal (aq) the time of the emission of the light (wavelength) the orientation of the distillation tower the amount of 11-cis-retinal used Thermometer measuring cylinder the darkness of the room. Materials cis-retinal light source beaker distillation tower stop-watch Thermometer measuring cylinder Experiment

7. Experiment Procedure: • Take 3 different wavelengths of which are visible and 2 that are not. • Take 50 mL of 11-cis-retinal and replace the sample into a beaker. • Determine the initial temperature of the sample. • Place the light source 50 cm away from the beaker created in the previous step. • Emit the light (photon) of the first wavelength towards the beaker for about a minute. • Ensure that the laboratory has no extra light from the outside. • By using the distillation tower, determine the final temperature of the sample product. • Record the raw data. • Repeat the same procedure for the remaining samples. CAUTION: The laboratory must be darkened. http://cache.eb.com/eb/image?id=72150&rendTypeId=35

8. Experiment Result: • If the temperature change is greater than 0, the transformation of the retinal molecule did take place. • If the temperature remains the same, the reaction did not take place or there could be some systematic errors (like not emitting the light for long enough or the distance between the light source and the beaker was not close enough.) • If the temperature change is less than 0, the experiment is a failure and must be repeated, or the design of the experiment was not efficient. • Due to its structure, 11-cis-retinal has higher boiling point than all-trans-retinal. • Therefore, by observing the temperature change, one can determine the product of the reaction. • This experiment also investigates on which wavelength changes the structure.

9. Analysis:The Effect of Isomerism on physical properties Melting point and boiling point of the isomers. • The trans isomer has the higher melting point. • The cis isomer has the higher boiling point.

10. Trans: The image on the left side is trans. It has hydrogen molecules (pink circles) on opposite sides of the double bond. Trans is a prefix, meaning "across" or "on the opposite side". The prefix of the name explains the structure of the isomers. Cis: one on the right is cis. cis-structure has hydrogen molecules on the same side of the double bond. The word cis is a prefix, meaning "on the same side" Cis and Trans Structure http://www.chemguide.co.uk/basicorg/isomerism/geometric.html

11. Isomerism of Cis and Trans The molecule changes from cis - structure to trans - structure. • Cis - structure: overall bent. • Trans - structure: more linear or straight. This is the result of trigonal planar bonding, 120° bond angles, about the double bonds. • The absorption of photons in cis-retinal: electron moves to a higher-energy orbital. • This breaks the double bond and is temporarily changed into a single bond. • This allows the molecule to rotate around the single bond → changes the position of the molecule. • The double bond is reformed and locks the molecule and its position. Energy from light is necessary for this process: absorption of a photon changes the structure.

12. The Boiling Point of the Cis - isomer and Trans - isomer • Both molecules on the same side contain polar bonds: upper side (green side): partial negative charge lower side (white side): partial positive charge. Therefore, this cis isomer molecule is polar. Polar Molecule: • contains dipole-dipole interactions. • increase the boiling point because it requires more energy to break the bond.

13. The Boiling Point of the Cis - isomer and Trans - isomer Trans isomer still carries polar bonds but the molecule itself is non-polar. • The partial negative charge on the top of the molecule is balanced by an equivalent partial positive charge on the bottom. • Also, the partial charge on the left of the molecule is balanced by the charge on the right. • This lack of overall polarity causes van der Waals forces, weak bonding. • Therefore, less energy is required to break the bond, and so its boiling points are lower.

14. Self-Reflection Strength: • Time spent for preparation and discussion with the group. • Exchange in various ideas - awareness of the members. • The knowledge of related topics - organic chemistry, molecule bonding etc. • The knowledge gained from my father - briefly but directly. • Could stayed focused during discussions, preparations, and development of documents. • Motivation throughout the members. • Having members from biology and physics - clarifications + requests. • Organization skills. • Encouragements within the group members. • Being able to express personal thoughts. • Tendency to seek for reasons - “why”

15. Self-Reflection weaknesses/difficulties: • Lack of basic background knowledge on biochemistry. • Absence of required equipments -experiment. • The experiment was never taken in action. • Flexibility. • Further experiment could not have been planned. • Assumptions based - experiment was never put into practice. • Investigating on the mechanism; cause and effect. • Relating the two elements: human eye and camera lens - compare and contrast • The physical distance between the members. • Limitation on communication methods and tools. • The experiment planned could improve: by selecting certain wavelength, changing the distance of the apparatuses and time of the reaction, using an accurate distillation tower and other equipment, and absolute darkness of the laboratory - uncertain.

16. Self-Reflection Achievement: • Learned basic functions of human eye - interest in biochemistry and its functions. • Relationship between vision and light (photon) - making sense, in reality. • Major chemical and physical features of Cis and Trans isomers. • Planning an experiment on unfamiliar topic. • Discovering relationships between what has been studied and the topic. • Applying personal knowledge on the new topic. • Significance of corporate work. • Enjoyable and meaningful communications - successful discussions.

17. Conclusion: “Alone we can do so little; together we can do so much” -Helen Keller • Biology: Comparing the structure of the eye and the camera, there were many similarities through the steps on how they both see the image that comes through the lens. Although the camera and the eyes look completely different, when compared, they both have lens that focuses, apature and iris that controls the light intensity and also the retina and the film that reflects the light that is captured so that we can finally see the image that comes through the lens. • Physics:As investigated in the Pinhole Experiment, accommodation is a vital part in capturing clear images for human eyes and cameras. Although they both refract and focus light on the retina and the film through convex lenses to form an inverted image, their methods of accommodation differ greatly. • Chemistry: Photochemical events in vision involve opsin, a protein, and retinal isomers, vitamin A, in rhodopsin. The chemical reaction between photons and 11-cis-retinal is crucial for the further mechanism for humans’ visions; however, the chemical reaction between photons and silver halide on the film holds the significance for cameras. As investigation and further analysis suggests, trans - isomer has the higher melting point and cis - isomer has the higher boiling point due to its structure and intermolecular forces.