5 Photosynthesis Flashcards
In which cellular organelle does photosynthesis take place?
Chloroplast
Name 3 adaptations of a leaf and how they help maximise the rate of photosynthesis.
Large surface area- Absorb as much sunlight as possible.
Numerous stomata- Allows gas exchange to occur.
Network of xylem and phloem- Xylem brings water to the leaf cells and phloem carries away the sugar produced during photosynthesis.
What is the symbol equation for photosynthesis?
6CO2 + 6H20 ——light———-> C6H1206 + 6O2
What is the word equation for photosynthesis?
Carbon Dioxide + Water—–light—–> Glucose + Oxygen
Describe the structure of a chloroplast
Thylakoid- Disc-like structures that contain chlorophyll.
Grana- Stacks of thylakoids.
Stroma- Fluid-filled matrix.
Name the two stages of photosynthesis.
Light-dependent reaction
Light-independent reaction
What 2 things is the energy in LDR used for?
- Add an inorganic phosphate to ADP to make ATP.
2. Split water (photolysis) into H+ and OH- ions.
What is oxidation?
Loss of electrons
When a substance gains oxygen or loses hydrogen.
What is reduction?
Gain of electrons
When a substance loses oxygen or gains hydrogen.
What happens when a chlorophyll molecule absorbs light energy?
Pair of electrons are excited and are raised to a higher energy level. Electrons leave the chlorophyll.
What happens to the electrons that leave the chlorophyll?
They are taken up by an electron carrier.
In terms of oxidation and reduction, what has happened to the chlorophyll and electron carrier?
Chlorophyll= Oxidised
Electron carrier= Reduced
Electrons are passed along a number of electron carriers in a series of what kind of reaction?
Redox
Where is the transfer chain of electron carriers located?
In the membranes of the thylakoids.
Why do electrons lose energy at each stage of the transfer chain and what is the energy used for?
Each electron carrier is at a slightly lower energy level than the previous one.
Energy is used to combine Pi to ADP to form ATP.
What is the chemiosmotic theory?
The precise mechanism by which ATP is produced.
Explain the chemiosmotic theory.
- Protons are pumped into the thylakoid from the stroma using proton pumps.
- Energy for this is provided by the photolysis of water.
- Photolysis of water produces protons- concentration gradient of H+.
- Protons pass through ATP synthase channels and change it’s structure to allow ADP and Pi to join to form ATP.
What is the equation for photolysis of water.
2H20 —–> 4H+ + 4e- + O2
What happens to NADP when it takes up protons?
It becomes reduced NADP.
Why is reduced NADP important?
It is a potential source of energy for the plant.
What happens to the oxygen by-product from the photolysis of water?
- Used in respiration.
2. Diffuses out of the leaf.
Where does LDR take place?
In the thylakoids of chloroplasts.
Name 3 adaptations of a chloroplast for the LDR.
Thylakoid membrane- large surface area
Network of proteins in grana hold the chloroplast in a precise shape- maximum absorption of light.
Contain both DNA and ribosomes- Can quickly manufacture some of the proteins in LDR.
What 2 products of the LDR are used in the LIR?
ATP and reduced NADP.
Outline the stages in the Calvin Cycle.
- CO2 diffuses out of the leaf through the stomata into the stroma.
- The CO2 reacts with RuBP in a reaction catalysed by rubisco to produce 3GP.
- 3GP is reduced to 3TP by reduced NADP using energy from ATP.
- NADP is reformed and goes back to LDR.
What happens to the TP molecules in the LIR?
Some are converted into organic substances but most are used to regenerate RuBP using ATP from the LDR.
What does RuBP stand for?
Ribulose Bisphosphate.
Where does LIR take place?
Stroma of the chloroplast.
Name 3 adaptations of the chloroplast in the LIR?
- Fluid of the stroma contains all the enzymes needed to carry out the reaction.
- Stroma fluid surrounds the grana so the products of the LDR in the grana can readily diffuse into the stroma.
- It contains both DNA and ribosomes so it can quickly manufacture the proteins in the LIR.
What are the 3 factors affect the rate of photosynthesis?
- Temperature
- Light
- CO2
How can we measure the rate of photosynthesis of an aquatic plant?
By measuring the volume of oxygen produced by using a photosynthometer.
What is the light compensation point?
No net exchange of gases into or out of the plant.
