Degree Type

Honors Capstone Project

Date of Submission

Spring 5-1-2006

Capstone Advisor

Not Listed

Honors Reader

Not Listed

Capstone Major


Capstone College

Arts and Science

Audio/Visual Component


Capstone Prize Winner


Won Capstone Funding


Honors Categories

Sciences and Engineering

Subject Categories

Atomic, Molecular and Optical Physics | Other Physics | Physics


One important biological question is how the cell processes input information and decides what to respond. The cell can integrate the multiple inputs using linear and nonlinear dynamics to generate an appropriate output. This study focuses on the computerized recording of phototaxis (movement in relation to light direction) of Chlamydomonas cell populations response to green light, which activates the rhodopsin photoreceptor at their eyespots. The inputs are light stimulation of various wavelengths and intensities; and chemicals (IBMX, a PDE inhibitor; 2'5'-dideoxyadenosine, an adenylate cyclase inhibitor, 8-Br-cAMP-Na and Dibutyryl cAMP, cAMP analogs) affecting an important intracellular messenger, cAMP. The quantified output parameters include phototaxis distance, direction and sensitivity, and swimming rate/pattern. Quality and quantity of light, cell strains and conditions, intracellular cAMP, and concentrations of the chemicals play significant roles in determining the extent and direction of a cell's phototaxis behavior. Under this experimental condition, red light has a slight effect on the phototaxis direction; on the other hand, cAMP seems to regulate the phototaxis direction. Evidently, raising intracellular cAMP drives the cell movement toward the green light, while lowering the cAMP does the opposite. The switching of phototaxis direction is a clear indicator of decision making (to go toward or away from light). In combination with results from other techniques in the lab and using appropriate analytical tools, we hope to understand intracellular signaling of the pathway from rhodopsin stimulation to phototaxis behavior on decision making in particular. Eukaryotic cells including human cells have common basic features. Thus, this knowledge may lead to a better understanding of many diseases involving cell signaling and how cells make decisions.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.



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