Photosynthesis Flashcards
What is the balanced equation for photosynthesis?
6H2O + 6CO2 —> C6H12O6 + 6O2
What is photosynthesis?
A series of enzyme catalysed reactions that synthesise organic molecules like glucose. Other take olace in the chloroplast
What is oxidation?
Loss of electrons, gain of oxygen
What is reduction?
Gain of electrons, loss of oxygen
What factors can increase photosynthesis due to its enzymes?
Increased temperature
Increased KE
More enzyme substrate complexes being formed
How are thylakoids beneficial for photosynthesis?
The light dependent reaction occurs in thylakoids, as it contains electron transport proteins and chlorophyll to absorb light energy
Why are grana useful in photosynthesis?
They increase the surface area so can absorb more light energy for the light dependent reaction
What is the role of the stroma in photosynthesis?
It contains enzymes used for the light dependent reactions
What is the role of starch grains?
They store excess carbohydrtaes made in photosynthesis
Where does the light dependent reaction take place?
In the thylakoid
Explain what happens during the light dependent reaction
- chlorophyll absorb light energy, a pair of electrons gain energy and become excited, so leave the chlorophyll. This reduces the chlorophyll. This is PHOTIONISATION.
- PHOTOLYSIS occurs in the stroma, where water is split into hydrogen ions, electrons and oxygen.
- the pair of electrons pass through electron carrier proteins and undergo a series of redox reactions. This releases energy that is used to pump the hydrogen ions through the thylakoid membrane to create a conc. gradient between the stroma and thylakoid lumen
- the hydrogen ions then travel from the lumen ro the stroma through ATP synthase down the conc. gradient. This causes PHOSPHORYLATION (ADP + Pi —> ATP)
- the pair of electrons and hydrogen ions are added to NADP to make reduced NADP.
What is photoplysis?
Where LIGHT INDUCES the splitting of water into hydrogen ions, electrons and oxygen. H+ is used to reduce NADP, and electrons replace those lost in the chlorophyll
What photoionisation?
When the chlorophyll absorbe light and loses electrons
What is photophosphorylation?
Where LIGHT ENERGY is used to combine ADP with Pi to form ATP, using a hydrogen concentration gradient
What is chemiosmosis?
Energy released from electrons in the electron transport chain are used to actively transport H+ from the stroma into the thylakoid lumen.
Creates a conc. gradient
The H+ diffuse down gradient through ATP synthase, which causes photophosphorylation
How are the light dependent and independent reaction linked?
The light independent reaction rewuores ATP and reduced NADP that is produced during the light dependent reaction.
Where does the light independent reaction take place?
In the stroma lf the chloroplast.
What enzyme is used in the light independent reaction?
Rubisco
Explain the process of the light independent reaction
Carbon dioxide combines with a five carbon molecule (RuBP) to produce two molecules of glycerate phosphate. This reaction is catalysed by rubisco
ATP and reduced NADP are used to reduce the 2 molecules of GP to 2x triose phosphate.
The ATP provides the energy necessary for this reaction. The reduced NADP provides the hydrogen, and becomes NADP.
1/6 of the tripse phosphate is converted into glucose
5/6 is used to regenerate RuBP
State four limiting factors of photosynthesis
Carbon dioxide conc.
Light intensity
Temperature
Water availability
How does light intesnsity affect the rate of photosynthesis?
It provides energy to excite electrons, sl they leave the chlorophyll to ultimately make ATP.
How does carbon dioxide conc. affect the rate of photosynthesis?
It provides carbon to produce two molecules of GP, to ultimately make glucose
How does temperature affect the rate of photosynthesis?
It provides kinetic energy
How does water availability affect the rate of photosynthesis?
It releases H+ ions during photolysis, which are used to reduce NADP and in chemiosmosis
What are benefits of producing crops in a commercial glasshouse?
Higher yield
Crops can be grown out of season, so provides better economic return
Plants can be grown in places they would not normally grow
How do glass houses increase yield?
They allow farmers to controll limiting factors
This increases the rate of photosynthesis, to increase carbohydrates made
Therefpre more energy is available for growth, which increases yield.
Suggest how to comtrol light intensity, carbon dioxide concentration and temperature in a glasshouse.
Light- artificial lighting, using specifoc wavelengths.
CO2- use paraffin heaters, pump carbon dipxide into the glasshouse
Temp- ventilation, glass stops heat escaping, use heating mechsnisms snd thermometres
How could high temperatures lower the rate of photosynthesis?
High temperatures increase water loss by transpiration
Excessive water loss causes plants to close stomata to limit water loss
Carbon dipxide can therefore not enter the leaves, so photosynthesis decreases
How can water availability be increased in a glasshouse?
Using a humidifier- increases water vapour inside glasshouse
Decreases water potential gradient between leaves and air
So less water diffuses out the spongy mesophyll, leading to less transpiration
How does photosynthesis affect the pH of cells?
It increases the pH of cells, more alkali because it decreases the concentration of carbon dioxide
