Photosynthesis Flashcards
(13 cards)
Where is the site of the light independent reaction of photosynthesis?
Stroma
Where is the site of the light dependant reaction of photosynthesis?
Thylakoid membrane/grana
Definition of photosynthesis
Process in which, light energy is absorbed and converted into organic molecules (ie chemical energy). The reduction of carbon dioxide to form organic molecules
What is the point of the light dependant reaction?
Produce ATP (by phosphorylation) and NADPH for the LIR
Photosynthesis word equation
carbon dioxide + water -> glucose + oxygen
Photosynthesis symbol equation
6CO2 +6H2O -> C6H12O6 + 6O2
Plants carry out both photosynthesis and respiration. How do the rates of photosynthesis and respiration vary throughout the day?
In the daytime, the rate of photosynthesis(P) is greater than the rate of respiration(R). All of the carbon dioxide produced in R is used up in P. Some of the oxygen reduced in P is used in R, the rest is released. There is a net uptake of CO2 by the plant.
In the dark there is no P but R still occurs. There is now an uptake of oxygen by the plant and a release of CO2. For a plant to grow the overall rate of P must be greater than the rate of R. This leads to GPP.
What is the compensation point?
the point at which the rate of photosynthesis = rate of respiration.
what is meant by reduction?
gain of electrons, gain of hydrogen or loss of oxygen. (transfer of electrons releases energy so a substance that is reduced gains energy.
what is meant by oxidation?
oxidation is the loss of electrons, loss of hydrogen or gain of oxygen.
what are coenzymes?
transfer hydrogen from one molecule to another. NADP for photosynthesis. NAD and FAD in respiration. (e- also transferred)
Light Independent reaction model answer.
CO2 diffuses into the leaf through the stomata and into the stroma of the chloroplast. Ribulose Biphosphate (RuBP) combines with a molecule of carbon dioxide catalysed by the enzyme RUBP carboxylase (also known as rubisco) An unstable 6 carbon compound is formed which immediately breaks down into two 3 carbon molecules of glycerine-3-phosphate (GP). The GP is reduced to Triose Phosphate using electrons and hydrogen ions from NADPH and energy from ATP produced during the LDR. 1/6 of those triose phosphate is used to make hexose sugars. e.g. glucose and other organic molecules and 5/6 are used to resynthesize RuBP, this time using ATP as a source of phosphate. NADP,ADP and Pi all return to the thylakoid membrane for use in the light dependant stage.
What can you notice about any reaction that produces carbon dioxide?
reduces number of carbon atoms in the molecules in the pathway.
