Chapter 17, Problem 13CP

Summary Introduction

To determine:

The effect of deficiency of phosphodiesterase activity in photoreceptors, on the vision of a person.

Introduction:

Phosphodiesterase is the enzyme that breaks the bonds between the phosphate groups. The enzyme is activated when the opsin is activated, transducin molecule acts upon its inactive form. In the cell, the phosphodiesterase catalyses the breakdown of cyclic GMP, that decreases the concentration of cyclic GMP. The lower levels of cyclic GMP induce the closing of the sodium ion channels which causes hyperpolarization of the plasma membrane. This decreases the release of neurotransmitters which sends a signal that the photoreceptor has absorbed a photon.