photosynthesis Flashcards
how does photosynthesis transfer energy from light to carbohydrate
involves taking CO2 and reducing it (adding Hydrogen) to produce carbohydrate. The hydrogens from the water and the energy absorbed by chlorophyll.
LD = photolysis is when splits water to get the hydrogens and photophosphrylation is when ATP is produced from the hydrogen energy. the coenzyme NADP is reduced using the hydrogens
LI = energy from ATP and NADP can reduce to CO2 to produce carbohydrtaes.
structure of chloroplasts and function
has a double membrane
stroma = site of LI stage; it has enzymes and other substances for the reactions of LI/ ribosomes to synthesise proteins/ starch grains to store the insoluble carbohydrate.
lamellae and thylakoid : hold carrier molecules that work as the ETC for LD
lamellae and thylakoid membranes : photosynthetic pigments are stored
grana = lots to increase SA, more LD reactions to happen and have as much light absorbed as possible
what is the role of pigments
absorbs some wavelengths of light and reflects other.
chlorophyll a absorbs slightly longer wavelengths of light than chlorophyll b.
carotene also absorbs blue light
chlorophyll absorbs red light
Photosystem 1 is 700nm and Photosystem 2 is 680nm
absorption and action spectra
the absorption spectra is how good the pigments are at absorbing energy from different wavelengths of light.
the action spectra shows the photosynthesis rate are different wavelengths of light. the rate of photosynthesis is highest at the blue-violet and red regions of light spectra a
cyclic photophosphorylation
only involves photosystem 1 and only makes ATP
Light energy is absorbed by the PS1
passed to reaction centre
This energy excites the electron and raises it to the elevated state and out of chlorophyll. (pigments are in thylakoid membranes) = Photoactivation
exited electrons go through the ETC in thylakoid membranes, go through redox reactions and lose energy. The energy lost are used active transport protons from stroma, across thylakoid membrane, into thylakoid space (chemiosmosis stuff)
Photoactivation
emission of an electrons from a molecule as a result of the absorption of energy from light.
non-cyclic photophosphorylation
Z scheme with both PS1 and PS2
PS2 makes ATP and PS1 makes Red NADP through the enzyme NADP
PS1 uses the electron from PS2 but PS2 uses the electron from photolysis (H2O -> 2H+ + e- + 1/2O2)
ATP and Red NADP made in LD to use in LI
photolysis
oxygen-evolving complex is the enzyme for photolysis.
H2O –> 2H+ + 2e- + 1/2O2
The H+ combine with e- to make Red NADP
2H+ + 2e- + NADP –> Red NADP
the oxygen is a waste product and diffuses out of chloroplast and used in mitochrondira for aerobic respiration.
LI
CO2 + RuBP (ribulose biphosphate) –rubisco–> 6C
6C makes 2 x 3C (glycerate-3-phosphate)
2 x 3C makes 2 x 3C (triose phosphate)
Red NADP and ADP are oxidised
reducing agents reduce the GP into a carbohydrate
TP can be used to regenerate RuBP which requires ATP
TP also condense into Hexose phosphate to make starch, sucrose and cellulose.
the carbohydrates from the LI can make amino acids = proteins and glyercol and fatty acids = lipids
limitation
light intensity, wavelenght, CO2, water, Temperature, prescence of pigments
Light intensity, CO2 concentration and temperature are limiting factors
effect of light intensity
as light intensity increases, photosynthesis rate increases,
greater light intensity, more light energy and faster LD stage
after it begins to plateau as light intensity is no longer a limiting factor
effect of CO2
The rate of photosynthesis increases as carbon dioxide concentration increases:
more CO2, faster Calvin cycle
after it begins to plateau as CO2 is no longer a limiting factor
effect of temperature
As temperature increases the rate of photosynthesis increases as the reaction is controlled by enzymes
as Ek increases however, too high temperatures may denature enzymes.
LD are driven by light energy so not affected but Calvin doesn’t use light and uses kinetic energy and are enzyme controlled
chromotography and how to calucate Rf values
Chromotography is a technique that can separate substances in a mixture according to their solubility in a solvent
Rf = distance by pigment spot/distance of solvent
A high value means the the spot travelled high, it moved with the solvent, very well soluble in solvent.
limiting factors of photosynthesis rate with aquatic plants
Limiting factors =
- Light intensity : altering the distance of the light source
- Wavelength: using colour filters with same light intensity
- CO2: adding different amounts of NaHCO3 to the water surrounding water
- Temperature: Using beaker to maintain temperatures
Measure the volume of O2 released from plant (aerated??????)
cut discs of a plant and push them to the bottom, as they photosynthesis and release oxygen, these bubbles float to the surface. the faster the bubbles the faster photosynthesis
