Lecture 9 - Photosynthesis Flashcards
Where does photosynthesis occur?
In two parts in the chloroplast
What two parts of the chloroplast does photosynthesis occur
Thylakoid
Stroma
What are the three membranes of chloroplast?
Outer
Inner
Thylakoid
What are the three compartments of the chloroplast
Intermembrane space
Stroma
Thylakoid space
What is the thylakoid space
Space within thylakoids where we build up proton gradient
Where do light reactions take place?
On the thylakoid membrane
Where does carbon fixation occur?
Stroma
What are pigments
Pigments are molecules that can absorb light. Pigments enable complexes to absorb light.
What is the purpose of light reactions?
To capture light energy and convert it to chemical energy. This happens with pigment and protein complexes embedded in the thylakoid membrane.
What is a photosystem?
They are protein complexes that contains the chlorophyll
How do photo systems capture light energy and what is it then used for?
The chlorophyll present in the photosystem absorbs light energy. This light energy then produces high energy level electrons. These high energy electrons then travel through the photosynthetic electron transport chain.
What proteins are involved in the photosynthetic electron transport chain?
Photosystem ll Cytochrome complex Photosystem l Electron carrying molecule (NADP+H+) ATP synthase
What happens at photosystem ll in the photosynthetic electron transport chain?
Light energy come in and excites the electrons. This causes the movement of 2 electrons from the chlorophyll to move through photosystem ll and then leave photosystem ll. The electrons then move to the cytochrome complex
What happens at the cytochrome complex in the photosynthetic electron transport chain?
The two electrons then move through the cytochrome complex which causes it to lose some of their energy. The energy lost is then used to pump protons from one side of the membrane to the other. The 2e- then go to photosystem l.
What happens at photosystem l in the photosynthetic electron transport chain?
The 2e- then travel through photosystem l. Photosystem l absorbs more light energy which transfers to the electrons to excite them. The electrons then sit in electron carrying molecule NADP+ + H+ creating NADPH.
What happens at ATP synthase in the photosynthetic electron transport chain?
The protons that where pumped through the membrane by the cytochrome complex is used to create a proton gradient which is used to drive ATP synthase to convert ADP + Pi to ATP
How does photosystem ll replace the two electrons?
Photosystem ll can draw electrons from water. When electrons are drawn from water O2 is also produced. As long as water is available there will be a continual chain of electrons.
What happens in the Calvin cycle?
In the Calvin cycle (carbon fixation) the ATP and NADPH produced in the light reactions are used to fix CO2 and produce carbohydrates.
Explain the steps of the Calvin cycle
- Fixation: 5 carbon molecule + CO2 -> 2 x 3 carbon molecules
- Reduction: 3 carbon molecule is converted into a different 3 carbon molecule and one carbon molecule leaves the system. (6ATP to 6ADP)(6NADPH to 6NADP+)
- Regeneration: convert the 3 carbon molecule back into the 5C molecule.
What is the output of the Calvin cycle?
A 3 carbon sugar that is converted to glucose.
6CO2 to C6H12O6
What happens with the glucose produced from photosynthesis?
The plant cells break down the glucose in the mitochondria using cellular respiration.
What is the ATP and NADPH formed during light reactions used for?
The Calvin cycle only, not for other cellular processes.
What are the inputs and outputs of photosynthesis?
Input: light, water and carbon
Output: glucose and oxygen
Describe the energy supply in plants and animals : Glucose
Both plants and animals breakdown glucose in cellular respiration to generate ATP. Animals have external source of glucose whilst plants generate glucose.
Describe the energy supply in plants and animals: ATP
ATP is generated in both respiration and photosynthesis. ATP synthase is responsible for ATP generation in both processes. A proton gradient is required across a membrane for this process to occur.
