3.1.5 Photosynthesis Flashcards
what is light energy absorbed by?
photosynthetic pigments
what is light energy absorbed for? (2)
- to generate ATP
- for Photolysis
pigments
chemicals found within the chloroplasts which absorb light energy and convert it into chemical energy
what do different pigments do?
absorb different wavelengths of light
Chlorophyll a absorbs…
blue light
Chlorophyll b absorbs…
red light
Carotenoids absorb…
violet, yellow & green light
what do carotenoids do? (2)
- extend the range of wavelengths absorbed
- pass the energy from absorbed light to chlorophyll for photosynthesis
absorption spectrum
shows the absorption of each photosynthetic pigment at different wavelengths of light
action spectrum
shows the rate of photosynthesis at each wavelength of light
what is the first stage of photosynthesis called?
photolysis
what does the absorbed light do to electrons in the pigment molecule?
excites them
what are the excited electrons captured by?
the electron transport chain
what does transfer of electrons through the ETC do?
releases energy to generate ATP by ATP synthase
what is water split itnto?
oxygen & hydrogen
does photolysis require energy?
yes
what happens to oxygen during photolysis?
it is evolved
what molecule are hydrogen ions transferred to during photolysis?
coenzyme NADP
second stage of photosynthesis
the calvin cycle
what does carbon dioxide become attached to when it enters the calvin cycle?
RuBP (ribuclose biphosphate)
what enzyme is oxygen attached to RuBP by?
RuBisCO
what does the attachment of oxygen to RuBP produce?
3PG (3-phosphoglycerate)
what happens to the 3-phosphoglycerate that is produced by oxyen, RuBP and RuBisCO?
it is phosphorylated by ATP and combined with hydrogen
what is produced when 3-phosphoglycerate is combined with hydrogen from NADPH?
G3P (clyceraldehyde-3-phosphate)
what is G3P used for? (2)
- to regenerate RuBP
- to synthesise sugars
what is an example of a sugar that G3P can be used to synthesise?
glucose
uses of glucose produced in the calvin cycle (3)
- used as a respiratory substrate
- synthesised into starch or cellulose
- passed onto other biosynthetic pathways
what do the other biosynthetic pathways that glucose may be passed onto lead to the formation of?
a variety of metabolites eg. DNA, protein and fat
