Photosynthesis Flashcards
Define a photosynthetic pigment
A molecule that absorbs a specific wavelength of light. Different pigments absorb different wavelengths.
Give the different photosynthetic pigments
1) Chlorophylls (a and b) - absorb red and blue-violet regions, reflect green wavelengths
2) Carotenoids (xanthophyll and B carotene) - absorb blue-green region, reflect yellow-orange wavelengths
Define absorbtion spectrum
A graph that shows how much light is absorbed at different wavelengths of light
Define action spectrum
A graph that shows the rate of photosynthesis at different wavelengths. It is measured by the mass of carbohydrates synthesised at different wavelengths
Describe and explain the relationship between the absorption spectrum and the action spectrum
They have similar correlation: the wavelengths of light that have the highest % absorbance are the wavelengths of light with the highest rate of photosynthesis. Therefore, wavelengths absorbed are those used in photosynthesis.
Describe the antenna complex
Contains photosynthetic pigments anchored to phospholipids in the thylakoid lumen that are held in clusters by proteins
Describe the reaction centre
Found below the antenna complex and contains 2 chlorophyll a molecules.
-PSI (P700) has a peak absorption of 700nm
-PSII (P680) has a peak absorption of 680nm
Describe nitrogen deficiency in plants
Stunted growth (fewer leaves and shorter), pale green leaves. Nitrogen is required to synthesis amino acids and proteins as it’s a components of ATP, DNA, RNA, so reduced cell division.
Describe magnesium deficiency in plants
Chlorosis, necrosis, and defoliation. Magnesium is a component of chlorophyll so less of it means less photosynthesis, thus less glucose, thus less respiration, thus lower ATP production, and thus cell death
Define the light compensation point
The light intensity at which a plant has no net gas exchange as the volume of gases used and produced in respiration and photosynthesis are equal
State limiting factors for rate of photosynethsis
1) Light intensity
2) temperature
3) CO2 concentration outside plant
4) degree stomata are open or closed
5) water supply. Too much = water logged = reduced mineral uptake
6) structure of leaf (SA)
7) availability of cholorophyll, carrier molecules and enzymes
State the law of limiting factors
The rate of a physiological process will be limited by the factor in shorted supply. Any change to the limiting factor will affect the rate of reaction
