Unit 1 - section 4 Flashcards
Name the 3 domains of life?
Eukaryotes
Bacteria
Archaea
What is the role of bacteriarhodopsin in the photoreceptor system in archaea?
Generate a potential difference by absorbing light to pump protons across the membrane
What pigment absorbed light energy in plant cells?
Chlorophyll
What is the effect of light absorption on the movement of hydrogen ions in the chloroplast?
When chlorophyll absorbs light an electron is passed to a higher energy level. It passes along a series of protein carriers. This process causes hydrogen ions to be pumped across the membrane
How does light absorption in plants drive ATP synthase?
The hydrogen ions that have been pumped across the membrane diffuse through ATP synthase, producing ATP
Which membrane protein is important in the animal photoreceptor system?
Opsin
How does opsin form the photoreceptor proteins in the eye?
Opsin binds with retinal to form rhodopsin (photoreceptor proteins in the eye) different forms of opsin combine with retinal to give sensitivity to specific wavelengths of light
What 2 cell types are found in animal eye structures that are involved in light absorption?
Cone cells
Rod cells
Compare the sensitivity of of cone and rod cells
Cone cells are not as sensitive to light as rod cells but allow us to distinguish colour in daylight
Rod cells are more sensitive to low levels of light because they contain rhodopsin which allows them to absorb a wider range of wavelengths and amplify the signal more
What is rhodopsin and how and where is it formed?
It absorbs a wide range of wavelengths and causes a greater degree of amplification from a single photon of light allowing sensitivity at lower light levels
Rhodopsin is formed from opsin and retinal and is formed in the membrane of the retina
How do rod cells give sensitivity at low light intensities?
Rhodopsin amplifies the received signals.
When a signal is received by receptor proteins it is amplified by a protein cascade
What are the 4 different wavelengths of light that can be absorbed by different forms of opsin in cone cells?
Red
Green
Blue
UV
Describe the events following the stimulation of a rhodopsin molecule by one photon of light to the generation of a nerve impulse
When stimulated by one photon of light a rhodopsin molecule activates hunderends of G-protein molecules which activates hundreds of molecules of an enzyme. If the enzyme triggers sufficient product formation a nerve impulse will be released.
