Photosynthesis Flashcards
What is an autotroph? Therefore what can we call plants?
Auto troph is an organism that makes its own molecules, a plant is therefore a photo autotrophs
Where does photosynthesis occur?
Chloroplasts
Describe the internal structures of a chloroplast
Outer membrane
Inner membrane
Thylakoids which are the individual disk like sections, and granum which are stacks of thylakoids
Grana are connected by an intergranal lamallea
What is a plants compensation point?
Where the plant respires at the same rate as it photosynthesises.
There is no net gain or loss of carbohydrates
Give up to six adaptations of the plant to increase photosynthesis
Large surface area of the thylakoids= more electron carrier
Leaves are thin which reduces diffusion distance
Leaf arrangement prevents areas shading each other
Transparent, allows light to reach the mesophyll
Many stroma to help gaseous exchange
Opening and closing of stroma
The light has two roles within the light dependant reaction give the end results of both of these roles.
Adds Pi, to ADP
Photolysis
What is the role of an accessory pigment?
Cause energy to be directed towards a reaction centre, i.e. The chlorophyll
What is a photosynthetic pigmemt?
A pigment that absorbs specific wavelength of light energy
What inorganic ion is present within the chlorophyll?
Mg2+ (prophyrin group)
Describe the light dependant reaction role on the chlorphyll to form ATP
Light energy excites an electron within A chlorophyll molecule
Electron leaves chlorophyll (hence chlorophyll is oxidised)
Electron carrier accepts the electrons
Redox reactions occur, down a electron transport chain, energy is lost at each stage
Energy used to pump hydrogen ions across the thylakoids membrane.
Only way hydrogen ions can diffuse back through is through ATP synthase channel proteins, which catayse ATP synthesis.
Other than being pumped through ATP synthase molecules where else may a proton move to during photosynthesis?
NADP may accept the proton = NADPH
Show the equation for photolysis
2H2O —> 4H+ + 4e- + O2
State where the three products of photolysis go to (photosyntheis)
Oxygen- used in respiration
Protons - add to H+ gradient
Electrons- replace the lost electron in the chlorophyll
Where does the light independent stage take place?
Stroma
Give three adaptations that help the light independent reaction
Heavily abundant enzymes
Short diffusion pathway between the grana and stroma
Why, despite its name, wont the light independent reaction occur in dark conditions?
It uses the products; ATP and NADPH which come from the light dependant reaction.
ATP also activates RuBisCo
Proton pumoing changes pH which is more optimum for RuBisCo
Describe the light independent stage.
Co2 diffuses through the stomata into the stroma of the chloroplast
RuBisCo catalyses the carbon fixation onto ribulose bisphosphate
Product is unstable and breaks down to glycerate three phosphate
NADPH reduces glycerate 3 phosphate to triose phosphate, ATP supplies energy
Some triose phosphate molecules go back to be Ribulose bisphosphate where as others are converted
What are the limiting factors of respiration?
CO2 H2O Light intensity Enzyme availability Number of ATP synthase molecules
Describe how light intensity will act as a limiting factor?
Powers the light dependant reaction
Therefore has an effect on the amount of NADPH and ATP
Less of these products leads to a disruption in the calvin cycle
Triose phosphate will not be produced from the reduction of glycerate-3-phosphate
Ribulose bisphosphate wont be regenerated
Also is a stimulant to the opening of stomata
Leads to other changes within other limiting factors
Describe how [CO2] is a limiting factor
CO2 is needed to bind to ribulose bisphosphate
Accumulation of RuBP
Decline in triose phosphate and glycerate bisphosphate
Describe how temperature is a limiting factor to photosynthesis.
Lower temperatures photosynthesis slower due to kinetic theory
Where tempertures are above 30 oxygen reacting woth RuBisCo is favoured over carbon
Where tempertures rise of 45 degrees denaturing may occur e.g. RuBisCo
Give two ways in which water stress leads to the reduction in photosynthesis
Lack of water = plasmolysis = longer diffusion pathway
Abscisic acid is released (a hormone) closes the stomata, whilst successfully preventing water loss also prevents CO2 entering hence stops carbon fixing in light dependant
What limitations are there to using oxygen production as a measurement for photosynthetic rate?
Some oxygen is used in respiration
Meausring gas production, not all gas is oxygen i.e. Some nitrogen
Describe the roles of the following within a photosynthometer
- water bath
- Potassium hydrogencarbonate
- syringe
Water bath maintains a constant temperature
Potassium hydrogen carbonates concentration can be adjusted to change/ control carbon dioxide conc
Syringe allows for the movement of the air bubble within the tube
What experiment was used to prove Calvins cycle
Lollipop experiment
What is the basic idea of calvins ‘lollipop experiment’?
Add radioactive Carbon 14 to a flask with algae in it.
Drop samples at intervals into hot alcoholic solution (stops synthesis)
Split the chemicals by chromatography
See at which points which chemicals were radioactive i.e. How lomg alage had been left in flask
