Photosynthesis- Topic 5 Flashcards
What is the word equation for photosynthesis?
Carbon dioxide + water (light energy) —> oxygen + glucose
What is the symbol equation for photosynthesis?
6CO2 + 6H2O (light energy) —> 6O2 + C6H12O6
Why do plants photosynthesise?
- Energy for biological processes
- Organic molecules needed for growth
- Respiration (O2 is a product)
What else does photosynthesis benefit?
- If the plant is consumed organic molecules provide energy
2. Oxygen produced is released into the atmosphere and is available for other organisms
The structure of a leaf: waxy cuticle
Prevents water loss and allows the light needed for photosynthesis through
The structure of a leaf: upper epidermis
Protective layer that reduces water loss
The structure of a leaf: palisade cells
Packed with chloroplasts containing chlorophyll that trap light
The structure of a leaf: spongy mesophyll
Gas exchange
The structure of a leaf: lower epidermis
Guard cells that allow water and gases in and out
What is a photosynthetic pigment?
A coloured biological compound that is present in chloroplasts and photosynthetic bacteria which captures light energy for photosynthesis
What are the two types of photosynthetic pigments?
Chlorophyll and carotenoid
What is the absorption spectrum?
The range of amount of light of different wavelengths absorbed(Rate of absorption against wavelength)
What is the action spectrum?
The rate of photosynthesis against the wavelength of light
The structure of a chloroplast: double membrane
Controls what gets in and out of the cell
Structure of a chloroplast: inner membrane
Folded to form thylakoids
The structure of a chloroplast: thylakoids
Contains pigment. The first part of photosynthesis the light dependent reaction takes place here
The structure of a chloroplast: inter-granal thylakoid
Extensions of the membrane. Also used for light dependent reaction
The structure of a chloroplast: Granum
Stacks of thylakoids which increase surface area
Structure of a chloroplast: stroma
Jelly like material that contains enzymes the second part of photosynthesis the light independent reaction takes place here
Name 3 molecules involved in photosynthesis
Adenosine triphosphate (ATP) Adenosine diphosphate (ADP) Nicotinamide adenine dinucleotide phosphate (NADP)
What happens with ATP in the light dependent reaction?
ATP is synthesised from ADP + P- this is called phosphorylation. Since light energy is used here it is called photophosphorylation.
What happens to ATP in the light independent reaction?
ATP is hydrolysed into ADP + P- when this bond is broken energy is released
What are the nucleotides joined by in NADP?
Phosphate groups
What can NADP accept? What does this cause?
NADP can accept electrons to be reduced NADP. (NADPH) this reduced NADP can be oxidised back to NADP releasing electrons.
What is OILRIG?
Oxidation Is Loss of electrons Reduction Is Gaining electrons
What is the location of the light dependent stage of photosynthesis?
Thylakoids membrane
What is situated in the thylakoids membrane?
Light harvesting Photosystems (I) (II) that have chlorophyll at their centres
What are the products of the light dependent reaction that pass on to the light independent reaction?
- Reduced NADP
2. ATP
What are the products of the light dependent reaction that leave the plant?
Oxygen molecule
What are the products of the light dependent reaction that are reused in another part of the light dependent reaction?
- H+ ions
2. Electrons
What is the location of the light independent stage of photosynthesis?
Stroma
What are the products of the light independent reaction the pass back into the light dependent reaction?
- NADP
- ADP
- Inorganic phosphate
What are the products of the light independent reaction that are used in other processes?
GALP is used to build carbohydrates, amino acids and lipids
Using the products-GALP
- Used directly in glycolysis
- Some is converted to acetyl coenzyme A and used to synthesise lipids
- Gluconeogenesis- converted to glucose which can be further used to build up more complex carbohydrates.
Alternative routes- what happens to plants in hot weather?
- in hot conditions plants will close the stomata so less water is lost
- this means less CO2 can get in and more O2 is trapped
- O2 inhibits Rubisco
Alternative routes- C4 pathway
An extra stage before photosynthesis which synthesises more carbon dioxide. It takes place in specialised cells near the surface.
Alternative routes- CAM plants
Open stomata at night to allow CO2 through then uses a CO2 producing mechanism.
Factors affecting the rate of photosynthesis- light intensity
- as light intensity increases the rate of photosynthesis increases.
- until a plateau where a further increase in light intensity will not increase the rate of photosynthesis
- this means something else is limiting it (probably CO2 concentration)
What does light intensity affect?
-light intensity affects GALP- less reduced NADP and ATP from LD reaction= less GALP and more GP.
Factors affecting the rate of photosynthesis- temperature
- increasing the temperature increases the kinetic energy
- this increases the successful collisions of enzyme and substrate
- which increases the rate of photosynthesis
- until the enzyme denatures with further temperature increase
What does temperature effect?
Rubisco- no CO2 fixing= build up of RuBp
Factors affecting the rate of photosynthesis- CO2 concentration
- as CO2 concentration increases so does the rate of photosynthesis
- until plateau
- something else is limiting it (probably light intensity)
What does CO2 concentration affect?
RuBp- less carbon fixing= more RuBp
What is the compensation point?
When a plants photosynthesis rate= respiration rate (no oxygen will be released into the atmosphere)
