early days of photosynthesis

prokaryotic photosynthesis likely made oxygen in the atmosphere, laying the evolutionary foundation for eukaryotic photosynthesis to develop

reaction center

contains special molecules that can transform light energy into chemical energy

antenna pigments

gather light and bounce energy to the reaction center (e.g. chlorophyll a, chlorophyll b, carotenoids)

pigments

light absorbing molecules in chloroplasts

chlorophyll a

absorb blue-violet and red, directly feeds light reactions, looks green because reflects green light

chlorophyll b

absorbs blue and orange light, looks yellow-green because reflects that light, does NOT directly participate in light reactions but feeds by broadening the range of light a plant can use and giving energy to chlorophyll a

carotenoids

absorb blue-green light, reflect yellow-orange light, some pass light energy onto chlorophyll a while others dissipate excess light energy to stop damage

absorption spectrum

shows how well a certain pigment absorbs electromagnetic radiation, opposite of emission spectrum, light absorbed is plotted as a function of radiation wavelength

photon

fixed quantity of light energy, shorter wavelength = greater energy

What happens when a pigment absorbs a photon?

one electron gain energy, raised from ground to an excited and unstable state, loses excess energy as heat or light as returns to stability

chlorophyll solution

emits heat and reddish photon afterglow (fluorescence) as electrons go from excited to ground

primary electron acceptor

reduced when illuminated chloroplast chlorophyll transfers excited electrons to it, while chlorophyll is oxidized, ATP and NADPH are made

photosystem

chlorophyll a, chlorophyll b, and the carotenoids are clustered together in the thylakoid membrane in 200-300 molecular assembled

photosystem 1

P700 chlorophyll a, best absorbs 700 nm of red light, works with different proteins from photosystem 2

photosystem 2

P680 chlorophyll a, best absorbs 680 nm of orangey-red light, works with different proteins from photosystem 1

photophosphorylation

when light energy is used to make ATP in autotrophs

photolysis

when water is split into oxygen, hydrogen, ions, and electrons to replenish the thylakoid's electrons

light dependent reactions

occur in the grana of chloroplast (thylakoids) with antenna pigments, water is oxidized so oxygen escapes as gas and H2 goes into the NADP+ electron carrier which turns into NADPH

What comes into light dependent reactions?

water, ADP, NADP+

What comes out of light dependent reactions?

ATP, NADPH, O2

cyclic phosphorylation

some plants perform cyclic electron flow, generating only ATP and no NADPH, only in photosystem 1 (once an electron is displaced from the photosystem, it is passed down electron acceptor molecules and returns to photosystem I)

light independent reactions (Calvin cycle)

use products of light reactions to make sugar, in carbon fixation CO2 is used to make carbohydrates in the stroma

What comes into dark reactions?

9 ATP, 6 NADPH, 3 CO2

What comes out of dark reactions?

O2, glucose, ADP, NADP+

What is reduced in photosynthesis?

carbon dioxide

What is oxidized in photosynthesis?

water

photosynthesis equation

12 H20 + 6 CO2 -sunlight-> C6H12O6 + 6O2 + 6 H2O

oxidized

loses electrons, oxygen takes the greater ratio in the substance

reduced

gains electrons, hydrogen has a greater ratio in the substance

What happens to the hydrogens in the electron carriers?

they go through the Calvin cycle to become a part of glucose

Where does carbon dioxide goes?

both the carbon and oxygen of glucose are from here

What does the sunlight do?

its energy is stored in the chemical bonds and it initially excites water's hydrogen electrons

When do dark reactions run?

primarily during the day, when light reactions are although they are still independent of light technically