2. The release, by one cell, of substances that transmit information to other cells. Definition:

3. Why does cell signaling occur in the eye? Without cell signaling we would all be blind. None of the chemicals and proteins would be combining to help us capture a visual of what is around us. Cell signaling occurs in all multicellular organisms providing an indispensable mechanism for cells to influence one another.

4. Sclerotic Coat –Creates the “white” of the eye. –This admits light into the eye. Choroid Coat –Mid-layer; deeply pigmented with melanin –Forms the iris of the eye and is responsible for the eye color. Retina –Inner layer of the eye –Contains light receptors: 1) rods- night vision, contains light absorbing pigments (sensitive to light) 2) cones- daylight, contains three types: 1) red absorbing cones 2) green absorbing cones 3) blue absorbing cones (These allow us to see in color)

5. There are 100 trillion cells in your body and each share a key feature that most bacteria and protists lack. This is when your cells touch and communicate with one another. When they send and receive chemical signals, they coordinate their behavior so that your body functions as a whole.

6. Contains two types of cells: –Bipolar cells –Ganglion cells These form a path from the rods and cones to the brain. The ganglion cells are always active. When dark, they generate “action potentials” and conduct them back to the brain. These “action potentials” travel along the optic nerve. Vision is based on this modulation of nerve impulses.

7. Within the cell, there are receptor proteins. They each have a three dimensional shape that fits the shape of a specific signal molecule. For example, how a substrate fits specifically into the enzyme. When a signal molecule approaches a receptor protein of the light shape, the two can bind. This binding produces a change in the receptor protein shape and induces a response in the cell. Binding of signals to receptor proteins causes GTP to bind a G-protein. G protein with attached GTP detaches to deliver the signal inside the cell. (This process happens inside the cell.)

8. A type of cell surface receptor that acts indirectly on enzymes or ion channels in the plasma membrane with the aid of an assisting protein are called a guanosine triphosphate (GTP)- binding protein. 1)G- protein linked receptors bind to the signal OUTSIDE the cell and to G proteins INSIDE the cell. 2) The G protein then activates an enzyme or ion channel, mediating the passage of a signal from the cell surface to the interior.

9. It’s not.

10. When a signal arrives, it finds a G-protein nestled into the G-protein linked receptor. The signal molecule binds to the receptor, then the G-protein linked receptor changes shape. The change in the receptor causes G-protein to bind to the GTP The G-protein can now diffuse away from the receptor. The “activated” complex of a G-protein with attached GTP is then free to start a number of events.

11. Rhodopsin is a G-protein linked receptor that activates hundreds of molecules of the G-protein. This receptor plays a major part in how we see a visual.

12. 1.The rods and cones within the eye pick up light and colors around you. 2. They then send these signals to the Receptor Proteins. (These signals are called photons)

13. 3. When the receptor proteins receive the signal, they change shape. This then activates the G-protein to bind to the GTP. 4. The G-protein and GTP will then activate an ion-channel. Creating a signal from the outside of the cell to the inside.

14. 5. The G-protein will then combine with a G-linked protein receptor. This will then activate the Rhodopsin. 6. When the Rhodopsin absorbs the photon, it activates 500 transducin molecules. Transducin molecules are a GTP regulated protein, composed of three subunits designated α, β and γ, involved in the visual process.

15. 7. When the transducin molecules are activated, they then activate another 500 molecules of Posphodiesterase. Phosphodiesterase is any of a class of enzymes that catalyze the cleaving of phosphodiester bonds, such as those between nucleotides in nucleic acids, to produce smaller nucleotide units. 8. These then hydrolyze 10,000 molecules of cyclic GMP. Cyclic GMP is a guanosine monophosphate nucleotide.

16. 9.Yeah I know getting boring…. 10. After the Cyclic GMP is hydrolyzed it closes the ion channels and preventing proteins and chemicals to get in. These chemicals and proteins are called “second messengers.” 11.Finally.. After closing the channel, the rods and cones send the signal to the brain. Cool Fact? All those 10 steps happen in about 1 second.

17. 1.Antibiotics: Such as Penicillin. 2.Antidepressants 3.Blood Pressure Medication 4.Steroids 5.Acne Medications

18. http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06b_ 07.pdf http://padui.org/information/effects-of-drugs-and-alcohol/ Bibliography

19. Cosette Hamad Irina Jury Mods 9-10 1/26/13