KA4 - Detecting and Amplifying an Environmental Stimulus Flashcards
Where can photoreceptor system proteins be found?
Across the three domains
In archaea, what do bacteriorhodopsin molecules generate?
Potential differences by absorbing light to pump protons across the membrane
In plants, what does the light absorbed by photosynthetic pigments drive?
An electron flow that pumps hydrogen ions across the thylakoid membrane of the chloroplast
In both cases, the resulting diffusion of hydrogen hydrogen ions back across the membrane drives…?
ATP synthase
In animals the light-sensitive molecule retinal is combined with…? What does this form?
Retinal is combined with a membrane protein opsin to form the photoreceptors of the eye
Once the photoreceptors of the eye detect light, what happens?
A cascade of proteins amplifies the signal
In rod cells, what is the retinal - opsin complex called?
Rhodopsin
What happens to a rhodopsin molecule when it is stimulated by a photon?
The rhodopsin molecule activated hundreds of G-protein molecules, which activate hundreds of molecules of an enzyme
If an enzyme triggers sufficient product formation, what may happen?
A nerve impulse may be generated
What does a very high degree of amplification result in?
Sensitivities at low light intensities
In come cells, what do different forms of opsin combine with?
Retinal to give photoreceptors proteins, each with maximal sensitivity to specific wavelengths (red, green, blue or UV)
What is the enzyme PDE called?
Phosphodiesterase
