Photo Overview 1
Name the two phases of photosynthesis.
Light Dependent Reactions
Calvin Cycle
Water is required for photosynthesis. In which reaction is water used?
Light Dependent Reactions
How are the electrons that are lost from photosystem 1 replaced?
They are replaced by electrons flowing from PSII through the ETC to PSI.
What is the necessary REACTANT of photosynthesis that is utilized during the Calvin cycle?
Carbon Dioxide
Name two alternative pathways that some plants utilize to conserve water.
C4 and CAM pathway
Where does the light dependent reaction take place?
Thylakoid Membrane
Carbon dioxide is required for photosynthesis. In which reaction is carbon dioxide used?
Calvin Cycle
How are the electrons that are lost from photosystem 2 replaced?
From the splitting of water
The purpose of the light independent reaction is to incorporate ____ from the atmosphere into molecules of _____.
CO2, G3P
What are three factors that could affect the rate of photosynthesis?
Amount of water and sunlight
Temperature
Where does the light independent reaction take place?
Stroma
What is the waste product of photosynthesis? Where does it come from and where does it go?
Oxygen!
Oxygen is produced when water splits it is then released through the stomata into the environment during LDR.
What happens to the hydrogen ions (H+) that are produced when water molecules are split?
They are built up inside the thylakoid lumen and are used later to power ATP synthase. H+ ions will flow passively from high to low concentration (from lumen to stroma) which will power ATP synthase. ATP synthase can harness this energy to convert ADP to ATP.
During the Calvin cycle, carbon dioxide joins with a 5- carbon sugar called _______ to form a very unstable 6-carbon molecule called PGA.
What is this process called?
RuBP, carbon fixation
How does the C4 pathway help a plant conserve water?
Plants that utilize the C4 pathway take in carbon dioxide and store it in the bundle sheath cells until it is needed for the Calvin cycle. With this pathway, the leaf is able separate carbon dioxide, store it in the bundle sheath, then close the stomata to prevent excessive water loss.
What is the name of the molecule that carries high energy electrons from the light dependent reactions to the Calvin cycle?
NADPH
The purpose of the light dependent reaction is to produce _____.
ATP and NADPH
Describe the flow of electrons during LDR.
Electrons held in PSII at p680 are excited by energy transferred to them by chlorophyll molecules. They are then transferred from PSII to the ETC where they move to PSI. They lose energy in this process and are then re-excited by chlorophyll molecules in PSI and transferred to NADP reductase which turns NADP+ to NADPH.
With the help of the high energy products from the light dependent reactions, _____ and _______, the PGA in the Calvin cycle will be converted into molecules of ______.
ATP and NADPH, G3P
How does the CAM pathway help a plant conserve water?
Plants that utilize the CAM pathway open their stomata only at night. Carbon dioxide is stored in the leaf at night and used during the day for photosynthesis. With the stomata closed during the day, water loss is reduced.
How many ATP and NADPH molecules are used during the Calvin cycle?
9 ATP (6 in reduction, 3 in regeneration)
6 NADPH (reduction)
What 4 molecules are constantly cycled/recycled between the light dependent and light independent reactions?
ATP/ADP and NADPH/NADP+
Describe how AND why H+ ions are transferred from the stroma to the thylakoid lumen.
H+ ions are transferred AGAINST the gradient (low to high) from stroma to lumen. The cytochrome complex absorbs energy lost by electrons flowing down the ETC and uses that energy to pull the H+ ions into the lumen. Those ions are then used to power ATP synthase where they will flow WITH the gradient (high to low) to create ATP.
The G3P molecules that are produced can be used for two things.
What two things?
1. To make glucose (sugar)
2. During regeneration to produce RuBP
What is a common problem of the C3 pathway? Explain.
When rubisco grabs hold of CO2 and adds it to a carbon chain, it often grabs hold of an oxygen molecule by mistake. This generates toxic molecules that plants have to expend energy to mop up. This process is called PHOTORESPIRATION and reduces the plant's efficiency.