3.2 - Photosynthesis Flashcards
What is the definition of photosynthesis?
A reaction in which light energy is used to split apart the strong bonds in water molecules in a process of photolysis in order to combine hydrogen with CO2 to produce the fuel glucose
Oxygen is waste product of this reaction and is released into the atmosphere
What affects the rate of photosynthesis?
Carbon dioxide concentration
Light intensity
Temperature
What is the site of photosynthesis and how is it adapted to its role?
- chloroplasts are the site of photosynthesis
- contains stacks of thylakoids called grana which contains chlorophyll
- contains stroma which is the fluid surrounding the grana, containing all the enzymes required for the light dependent stage of photosynthesis
What are the stages in the light dependent reaction?
1) Electrons are excited to a higher energy level by the energy trapped by chlorophyll molecules in the the thylakoid membranes
2) Electrons are then passed down the electron transport chain from one electron carrier to the next and this process generates ATP from ADP and inorganic phosphate in photophosphorylation
3) Reduced NADP is also generated in the light dependent stage as the electrons are transferred to NADP along with a proton
4) Both ATP and reduced NADP are used in light independent photosynthesis
What are the stages in a light independent reaction?
Also known as the Calvin cycle, its the final stage of photosynthesis which used ATP (source of energy) and reduced NADP (reducing power) to produce glucose
1) RuBP is combined with carbon dioxide in a reaction called carbon fixation, catalysed by RUBISCO
2) RuBP is converted into 2 glycerate 3- phosphate (GP) molecules
3) Reduced NADP and ATP are used to convert GP to gylceraldehyde 3-phosphate (TP)
4) Some of the TP molecules are used to make glucose, which is converted to essential organic compounds such as polysaccharides, lipids, amino acids and nucleic acids
5) Remaining TP molecules are used to reform RuBP with the help of ATP
