12) Unit 1 - Photoreceptor Systems In Plants and Eukaryotes Flashcards
What do plants use to convert light energy to chemical energy
Plants use photosynthetic pigment chlorophyll
Where is the photosynthetic pigment chlorophyll found
Within chloroplasts.
Inside the chloroplasts there are membrane bound compartments called GRANA.
The membrane surrounding the GRANA is called the thylakoid membrane.
This is where the chlorophyll is found - The thylakoid membrane
How does chlorophyll absorb light to pump protons across the membranes
1) in plants chlorophyll and other pigments are bound to protein molecules to form protein photosystems
2) when a molecules of chlorophyll absorbs light, one of its electrons are boosted to a higher energy level.
3) the electron passes along the electron transport chain
4) as the electron moves along the ETC hydrogen ions are pumped across the thylakoid membrane of the chloroplast
5) the hydrogen ions which are pumped across the membrane diffuse through ATP synthase, resulting in the production of ATP
What 2 types of Photoreceptor cells which convert light energy into electrical signals
- rods
- cones
Where are rod and cone cells found
The retina
What are rod cells
Light sensitive and allow vision in low light intensities
What are cone cells
Wavelength (colour) sensitive and allows colour vision
What Photoreceptor proteins are found in rod cells
rhodopsin
What is rhodopsin made from
A light absorbing molecules called retinal that is bound to a membrane protein called opsin
How does rhodopsin amplify light from a single photon of light and what does this result in
Opsin is a G-protein linked receptor which causes a cascade of proteins which amplify the signal within the cells.
This result in vision in low light intensities.
Describe the nerve transmission events that happened when rhodopsin is stimulated by a photon of light
1) When stimulated by a photon of light, rhodopsin becomes excited and a nerve impulse is generated
2) excited rhodopsin activates G-proteins which in turn activate many enzymes.
3) The enzymes close ion channels
4) Since the Na+ channels close, the membrane potential increases - this hyperpolarization stimulates a nerve impulse
What photoreceptor proteins are presents in cone cells
photopsin
what makes up photopsin and how does it allow coloured vision
different forms of opsin combined with retinal, each with maximal sensitivity to light. This allows detection of colours by the eye.
what must happen to trigger a cascade of events through opsin
a conformational change in retinal triggering a cascade of events
when is a nerve impulse generated
when the cascade of events is significant
