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Advanced Higher Bio
Unit 1 Photoreceptors
Question | Answer |
---|---|
what three organisms have photoreceptors | archaea, plants & animals |
What is the photoreceptor molecule in archaea | bacteriorhodopsin |
What is the photoreceptor molecule in plants and in what membrane structure is it found | photosynthetic pigments (chlorophyll) in thyalkoid of chloroplasts |
What is the photoreceptor molecule in animals and in what membrane structure is it found | rhodopsin in retina membrane |
What is rhodopsin made up of | opsin and retinal |
What is the function of retinal | light sensitive molecule in membrane |
What are opsin molecules | (membrane) proteins |
What is the function of rods versus cones | cones detect colour whilst rods detect light at low light intensity |
How are rods well adapted for their function | absorb wider wavelengths of light OR a very high degree of amplification results in sensitivities at low light intensities. |
How are cones well adapted to their functions | have more than 1 type of opsin whereas rods only have one type |
Explain how archaea photoreceptors work | bacteriorhodopsin absorbs photons of light which cause H ions to move across protein pump by AT and diffuse across ATP synthase to make ATP |
What molecule is pumped across membrane following excitation of light by bacteriorhodopsin | Hydrogen |
Explain how photoreceptors in plants work | chlorophyll absorbs photon of light which excites e that pass along ETC providing energy for H ion to be pumped across membrane & diffuse back across ATP synthase making ATP |
Explain how rhodopsin absorbs light in the human eye | 1 photon of light is absorbed by retinal which activates 100 G proteins which activate 1000 enzymes which close Na channels causing depolarisation creating nerve impulse |
Each opsin protein is for a specific colour. What FOUR wavelengths are they adapted to see | red, green, blue & UV |
Do rods or cones have rhodopsin | rods only |
What is pumped across the membrane in archaea | Hydrogen |
In animals what happens after 100's of G proteins have been activated | 1000's of enzymes activated |
What happens after 1000's of enzymes activated in animal vision | Na channels close/hyperpolarisation is sufficient product made |
What happens after Na channels close | nerve impulse generated due to hyperpolarisation |