ch. 7 photosynthesis 7.6 – 7.9. light reaction: converting solar energy to chemical energy...
DESCRIPTION
Visible light only forms a small percent of the electromagnetic spectrum. Can plants use more than just visible light for photosynthesis? No, only certain wavelengths, or colors of visible light?TRANSCRIPT
Ch. 7 PhotosynthesisCh. 7 Photosynthesis
7.6 – 7.97.6 – 7.9
Light reaction: converting solar energy to chemical energy
• Sunlight is what type of energy?
• Electromagnetic energy (radiation)
• What is a wavelength?
• Light travels in waves measured by the distance between two adjacent crests
• Visible light only forms a small percent of the electromagnetic spectrum. Can plants use more than just visible light for photosynthesis?
• No, only certain wavelengths, or colors of visible light?
• Do we see the wavelengths absorbed by the plant?
• No. We don’t see those colors.
• What happens to those other colors?
• Different pigments in chloroplasts absorb this light; (chlorophyll a, absorbs blue-violet and red, & chlorophyll b, absorbs mainly blue and orange light, & reflects (looks) yellow/green,
• What is a carotenoid?• Another type of
yellow/green pigment (absorbs blue-green light) in chloroplasts that helps protect plant from excessive light energy. (absorb & dissipates energy)
• What is the energy within a light wavelength called?
• Photons, They’re little packets, fixed units of energy in light.
• Since the shorter the wavelength = more energy (photons), which has more energy violet or red light?
• Violet has nearly twice as much energy!
• What does that photon do?
• When a pigment absorbs a photon, that chlorophyll’s electron gains energy (gets excited & jumps up), and releases (falls back to ground) that energy as heat or light
(aka: fluorescence)
• What is the first step in the light reaction?
• Solar-powered electron transfer from chlorophyll to primary electron acceptor.
• What makes up a reaction center?
• Collection of pigment molecules (chlorophyll a )and primary electron acceptor.
• What does the reaction center do?
• Triggers light reaction when chlorophyll donates an excited electron to primary e- acceptor, which passes an e- to electron transport chain.
• What is the overall combination of all this called?
• A photosystem
• How many types of photosystems are there?
• 2. Photosystem I & II.• How are they different?• Photosystem I, its
chlorophyll a absorbs red light best P700, and Photosystem II’s chlorophyll a absorbs an orange/red wavelength of light best P680.
Electron transport chain to make ATP, NADPH & 02
• Where do electrons go to when leaving PS 1?
• Chlorophyll loses 2e- to Primary e- acceptor which go down electron transport chain (ETC) to end up on NADP -> NADPH
• Are those electrons ever replaced?
• Yes, PS 2 loses its electrons to PS 1 passed down via the ETC.
• What about those electrons…are they replaced?
• Yes when H2O is split releasing O2 & supplying electrons to PS 2.
What is happening in the ETC
• What drives the transport of hydrogen ions (H+) across the thylakoid membrane?
• Arrangements of electrons being passes from one photosystem (protein ie: blue & purple) to another.
ATP synthesis in light reactions• What activates the pumping of
H+ ions out of the stroma?• The loss of energy each time
an electron goes from one photosystem to the other.
• Where do the H+ ions go?• They want to diffuse back in.• Do they ever get back in?• Yes, by facilitated diffusion via
ATP synthase, releasing energy to make ATP from ADP & P.
• What is this process called?• Photophosphorylation (ATP
production from initial input of light energy)