5.2.1 Flashcards
What is an autotrophic organism?
An organism that is able to photosynthesise, such as plants and algae
What are heterotrophic organisms?
Organisms that obtain complex organic molecules by eating other organisms
What is the overall equation of photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
Where does photosynthesis take place?
The chloroplasts
How are chloroplasts adapted to their function?
They have an inner membrane with transport proteins, many grana consisting of many thylakoids, photosynthetic pigments, proteins embedded in the grana, fluid-filled stroma, chloroplast DNA an ribosomes
How does the inner membrane with transport proteins aid the chloroplast?
It allows for transport of molecules into and out of the chloroplast. It controls what enters and exits
How do the grana aid the chloroplast?
This is where the light-dependent stage of photosynthesis takes place. They also contain lipids which help support the electron transport chain. They also contain ATP synthase
How do the photosynthetic pigments aid the chloroplast?
They absorb different wavelengths of light, allowing for more energy to be taken in for photosynthesis
How do the proteins embedded in the grana aid the chloroplast?
They catalyse reactions. They also hold pigments in place. Some of the proteins are also used as electron carriers
How does the stroma aid the chloroplast?
It is a site of chemical reactions, containing the enzymes for the light independent stage
How do the chloroplast DNA and RNA aid the chloroplast?
They allow for rapid synthesis of proteins required for photosynthesis
What is the light harvesting system?
It is composed of numerous secondary pigments and proteins
What is the function of the light harvesting system?
To absorb, or harvest, light energy of different wavelengths and transfer this quickly to the reaction centre.
What pigment is located in the reaction centre?
Chlorophyll a
What happens in reaction centre?
The reactions involved in photosynthesis take place
What are the light harvesting system and the reaction centre collectively known as?
A photosystem
What are the two stages of photosynthesis?
Light dependent stage and light independent stage
How many photosystems are involved in non-cyclic photophosphorylation?
2, PSII and PSI, or PS680 and PS700
What does the light absorbed by the photosystems do?
Excite electrons at the reaction centres
Where do the excited electrons go?
The excited electrons are released from the reaction centre of PSII and are passed to an electron transport chain. ATP is produced by the process of chemiosmosis
What is chemiosmosis?
The diffusion of H+ ions from a region of high concentration to a region of low concentration through a partially permeable membrane. The movement of the protons releases energy that is used in the synthesis of ATP from ADP and a Pi
How are the electrons lost by PSII replaced?
They are replaced by electrons produced by the process of photolysis
What is photolysis?
Light energy from the sun causes water molecules to split into hydrogen ions, electrons, and oxygen molecules
Where do the excited electrons eventually reach?
The electrons leaving the electron transport chain following PSI are accepted, along with a hydrogen ion, by the coenzyme NADP, forming reduced NADP
Where does the light-independent stage of photosynthesis take place?
The stroma of the chloroplast
How does the calvin cycle start?
Carbon dioxide enters the intercellular spaces within the spongy mesophyll og leaves by diffusion. It diffuses into the cells and into the stroma, where it combines with ribulate bisphosphate.
What is the binding of CO2 and RuBP called?
Carbon fixation
What catalyses the carbon fixation?
RuBisCO, and produces an unstable 6 carbon intermediate
What does the unstable 6 carbon intermediate do?
It breaks down into two 2 glycerate 3-phosphate (GP) molecules
What happens when GP receives a hydrogen and energy?
It forms TP, triose phosphate
What is the majority of TP used for?
Regeneration of RuBP so that the calvin cycle can continue
How many turns of the calvin cycle are there for 1 glucose molecule to be produced?
6, as 6 CO2 molecules must enter the calvin cycle. This means 12 TPs are produced, 2 of those being used to create the glucose molecule, while the other 10 are used to create 6 RuBP molecules
What are the factors affecting photosynthesis?
- Light intensity
- Carbon dioxide concentration
- Temperature
Why is carbon dioxide concentration a factor?
Carbon dioxide is needed as a source of carbon for the carbon fixation in the Calvin cycle
Why is light intensity a factor?
Light is needed as an energy source. As light intensity increases, ATP and reduced NADP are produced at a higher rate
Why is temperature a factor?
Temperature affects the rate of enzyme controlled reactions. As temperature increases, the rate of enzyme activity increases until the point at which the proteins denature.
What is the effect of reducing light intensity on the Calvin cycle?
Reducing light intensity reduces the rate of the light-dependent stage of photosynthesis. This reduces the quantity of ATP and reduced NADP produced. ATP and reduced NADP are needed to convert GP to TP. This means concentration of GP will increase while concentrations of TP and RuBP will decrease
What is the effect of CO2 and temperature on the calvin cycle?
At very low temperatures and very high temperatures, the concentrations of TP, GP and RuBP will all be low. Low CO2 concentrations would decrease the concentrations of GP and TP. However, the concentration of RuBP will increase, as it is being formed but not used up
