KA1b Photosynthesis Flashcards
state the role of photosynthetic pigments
absorb light energy to generate ATP and for photolysis
state the three fates of light when it hits a leaf
absorbed, reflected, transmitted
state the name of the principal photosynthetic pigment and accessory pigments
The principal pigments are chlorophyll a and b - they mainly absorb the red and blue wavelengths of light. carotenoids (carotene and xanthophyll) absorb light from other regions of the spectrum, extending the range of wavelengths absorbed. they are known as accessory pigments as they pass on the energy they capture to chlorophyll a and b
state the importance of having several photosynthetic pigments
increases the range of wavelengths of light that the plant can absorb and so increases the level of photosynthesis
state the difference between the action spectrum and the absorption spectrum
The absorption spectrum shows the wavelengths of light absorbed by the different pigments in a leaf. The action spectrum shows how effective the different wavelengths of light are at photosynthesis.
give an account of photolysis
in the chloroplast, light energy is absorbed by pigments and the energy excites electrons in the pigment molecules and raises them to a high energy state. these high energy electrons are captured by the primary electron acceptor and then transferred along the electron transport chain, releasing energy. this energy is then used by enzyme ATP synthase to generate ATP from ADP and Pi. some energy is also used to split water into oxygen - which is released as a by-product, and hydrogen - which is picked up by the hydrogen acceptor NADP to form NADPH.
give the fates of all the products of the first stage of photosynthesis
oxygen - released as a by-product. NADPH and ATP passed on to the next stage of photosynthesis, The Calvin Cycle
state the role of NADP
combines with hydrogen to form NADPH which is passed on to the second stage of photosynthesis - The Calvin Cycle
give an account of the Calvin cycle
enzyme rubisco fixes CO2 from the air by attaching it to RuBP to form an intermediate compound 3PG. 3PG combines with hydrogen from NADPH and is phosphorylated by ATP to form G3P. G3P is used for the synthesis of glucose and the regeneration of RuBP.
state the 3 fates of the sugar produced during photosynthesis
glucose may be used as a respiratory substrate, synthesized into starch or cellulose, or passed to other biosynthetic pathways
