Energy transfers - Photosynthesis Flashcards
What is the word equation for photosynthesis?
Carbon dioxide + water → glucose + oxygen
What determines the rate of photosynthesis?
Carbon dioxide concentration, light intensity and temperature.
What are the thylakoids?
Flattened sacs that contain photosynthetic pigments ( i.e. chlorophyll) in their membranes.
What are lamellea?
Membraneous extensions that connect thylakoids.
What is the stroma?
The fluid surrounding the thylakoids.
Where does the light- dependent reaction take place?
Thylakoid membranes or grana.
Where does the light- independent reaction take place?
In the stroma.
Name the stages of the light- dependent reaction.
Photolysis, photoionisation, and chemiosmosis.
Describe the process of photolysis.
Light energy is absorbed by chlorophyll in photosystem II and splits water into oxygen, H+ and e-. The H+ is picked up by NADP to form NADPH, which is used in the light independant reaction. The e- is passed along a chain of electron carrier proteins. The oxygen is either used in respiration or diffuses out of the leaf out of the stomata.
Describe the process of photoionisation.
Light energy is absorbed by the chlorophyll and excites electrons which raise an energy level to leave chlorophyll. Therefore, the chlorophyll has been ionized by light.
Describe the process of chemiosomosis.
The electrons that gain energy move along a series of proteins embedded within the thylakoid membrane. As they move along, they release energy and some of the energy is used to pump the protons from photolysis across chloroplast membranes. The protons pass through the enzyme ATP synthase, which result in the production of ATP. The protons combine with co-enzyme NADP to become NADPH.
Describe the process of the calvin cycle.
- CO2 reacts with ribulose bisphosphate (RuBP) to form two molecules of GP, a two carbon compound. This is catalysed by the enzyme rubisco.
- ATP and NADPH reduce GP to triose phosphate (TP).
- Some carbons from TP are used to make useful organic products, while the rest regenerates RuBP with energy from ATP.
What does the light- independant reaction use?
Carbon dioxide, NADPH and ATP.
