Vision begins when a lightdetecting molecule absorbs a photon, and our eyes are sensitive enough to allow us to detect changes to individual molecules in a cell. This requires amplification of a tiny signal to produce an electrical response large enough for our brain to notice through a process called phototransduction.

In this video, I show how this amplification is a physical process, relying on random motion and chance encounters, but that produces repeatable and reliable signals.

0:00 Introduction
1:05 Photoreceptors
1:36 Rhodopsin
2:04 Amplification
3:16 Cyclic GMP
4:01 Electric signal
6:16 Recovery
6:48 Conclusion

Animations were made in Blender and Maya by Kerry Kim. This video is copyright (c) 2021 by Kerry Kim. All rights reserved. No part of this video may be used without my prior written permission, except as permitted by U.S. copyright law.

3D coordinate files for proteins:

PDB ID: 7LFY
Xue, J. Han, Y., Zeng, W., Wang, Y., Jiang, Y. (2021) Structural mechanisms of gating and selectivity of human rod CNGA1 channel. doi: 10.2210/pdb7LFY/pdb

PDB ID: 7JSN
Gao, Y., Eskici, G., Ramachandran, S., Skiniotis, G., Cerione, R.A. (2020) Structure of the visual signaling complex between transducin and phosphodiesterase 6. doi: 10.2210/pdb7JSN/pdb

PDB ID: 1GOT
Lambright, D. G., Sondek, J., Bohm, A., Skiba, N.P., Hamm, H.E., Sigler, P.B. (1996) Heterotrimeic complex of a gtalpha/gialpha chimera and the gtbetagamma subunits. doi: 10.2210/pdb1GOT/pdb

PDB ID: 1F88
Palczewski, K., Kumasaka, T., Hori, T., Behnke, C.A., Motoshima, H., Fox, B.A., Le Trong, I., Teller, D.C., Okata, T., Stenkamp, R.E., Yamamoto, M., Miyano, M. (2000) Crystal structure of bovine rhodopsin. doi: 10.2210/pdb1F88/pdb