Photosynthesis Flashcards
Which ptotosystem appears first in the sequence of the light dependent reactions? [1]
Photosystem 2
Explain why the word equation of photosynthesis is not accurate of the whole process [1]
Implies that is a single step reaction and other products are also made
What is required to excite 2 electrons from photosystem 2? [1]
Photon of visible light
Give the word and symbol equation for photolysis [2]
Water –> Electrons + Oxygen + Hydrogen ions
H20 -> 2e- + 1/2O2 +2H+
Define the term photolysis [1]
The splitting of a molecule of water of water using visible light
When NADP is reacted with two electrons and two protons it becomes what? [1]
Reduced NADP or NADPH
What is the main difference between cyclic and non cyclic photo-phosphorylation? [2]
Non cyclic requires an external source of electrons whereas cyclic can keep using the same electrons over and over again
Draw out the stages of the light dependent reactions [4]
Check diagram in pack
State the reaction of chemeosmosis [1]
ADP + Pi -> ATP
Where does the energy require for chemeosmosis come from [1]
Energy given of at the electron transport chain
Where within the chloroplast does the light dependent stage take place? [1]
Within the thylakoid membrane
What is the initial reactant involved in the light independent reactions? [1]
RUBP
What does RUBP stand for? [1]
Ribulose biphosphate
What is the function of the rubisco enzyme? [1]
To fix CO2 to RUBP
Suggest where the CO2 for the fixing comes from? [1]
The air
What is the enzyme that fixes CO2 to RUBP called? [1]
Rubisco
After fixing CO2 and RUBP form what? [1]
GP
Why isn’t GP very useful? [2]
Very unstable so breaks apart easily
What does GP stand for? [1]
Glycerate (III) Phosphate
How does GP form TP? [2]
H+ donated from NADPH and energy required in the form of ATP
What does TP stand for? [1]
Triose phosphate
What happens to the majority of TP? [1]
It is phosphorylated and regenerates RUBP
What happens to the minority or TP? [1]
Used within the plant to form amino acids, sugars and lipids.
The light independent reactions are more commonly known as the what? [1]
Calvin - Benson cycle
Expalin what is meant by CO2 fixation? [2]
The conversion of a gaseous molecule into an organic compound
At what point in the Calvin cycle is there a reduction reaction taking place? [1]
GP is reduced when it gains e- from NAPDH in order to form TP
How many times must the cycle go around for one molecule of glucose to be produced? [1]
6
Explain why the light independent reactions could not carry on for a very long time without any light? [1]
Because you would run out of ATP and NADPH both of which are produced in the LDR so light needed in order for this to occur
Draw out the Calvin cycle [4]
See diagram in pack
List the three factors that limit the rate of photosynthesis [3]
Light intensity
Carbon dioxide concentration
Temperature
Suggest why temperature in a limiting factor? [2]
Because the greater the temperature the more Ke therefore the rate of enzyme controlled reactions is increased (CO2 fixation in the presence of rubisco
Suggest why CO2 concentration is a limiting factor? [2]
Because CO2 is required to be fixed to RUBP. The more CO2 the more GP can be produced so the Calvin cycle proceeds at a greater rate.
A horizontal line on a rate / factor x suggests what? [1]
Another factor - not x - is limmiting
What abbreviation can be used for concentration? [1]
[]
The light compensation point is what? [2]
The point at which there is no net CO2 uptake. I.e the CO2 produced in respiration = the CO2 used in photsynthesis
The light saturation point is what? [2]
The value of light intensity which gives the maximum rate of photosynthesis
