Photosynthesis Review Flashcards
Chlorophyll – structure and difference between chlorophyll a and chlorophyll b
Chlorophyll a - R=CH3 major photosynthetic pigment
Chlorophyll b - R=COH accessory pigment that absorbs light and transfers it to a
Electromagnetic radiation
a form of energy that travels at 3 x 108 m/s in wave packets called photons that include visible light
Photons
packets of EM radiation (also known as quanta)
Spectroscope
an instrument that separates different wavelengths into an electromagnetic spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies
Photosystems
clusters of photosynthetic pigments embedded in the thylakoid membranes of chloroplasts that absorb light energy
Action spectrum
graph illustrating effectiveness with which different wavelengths of light promote photosynthesis
Absorption spectrum
a graph illustrating the wavelengths of light absorbed by a pigment
Historical figures
a. Van Helmont
b. Joseph Priestley
c. Van Niel
d. Blackman
e. Engelmann
Accessory pigments –
a. Β-carotene
b. Xanthophylls
c. anthocyanins
a. a carotenoid pigment found in photosystems that also forms vitamin A in animals
b. pigments in chloro- plast membranes that give rise to the yellow colour in autumn leaves
c. pigments in vacuoles that give rise to the red colour in autumn leaves
Photosynthetically active radiation
wavelengths of light between 400 nm and 700 nm that support photosynthesis
Van Helmont
Early belief: plants obtained all their food from soil through their roots
Helmont planted a willow tree having determined the mass of the tree and the soil. Adding only water, he noticed that, after five years, the tree’s mass had increased by 74.4 kg, but the soil’s mass had decreased by 60 g (Figure 4).
Having proven that the soil was not responsible for the tree’s increase in mass, he incorrectly concluded that the absorption of water was responsible. (5 years)
Joseph Priestley
Accidentally discovered that gasses in the air play a role in photosynthesis
After burning a candle in a closed container until it went out, he placed a living mint plant in the container. After 10 days, he found that the candle could burn once again. In this way, he showed that plants release a gas into the air that supports combustion
The candle,as Priestley putit, “injures” the air in the bell jar and goes out.
A live plant is placed in a bell jar with a lit candle.
The candle “injures” the air and goes out. After several days, the candle can be lit once again. The plant “restores” the air.
Van Niel
Worked with purple sulfur bacteria, showed that the oxygen in photosynthesis is pro- duced by splitting water.
Purple sulfur bacteria absorb hydrogen sulfide, H2S(g), instead of water, H2O(l), and produce pure elemental sulfur as a waste product of photosynthesis instead of oxygen.
In green plants, the H2S(g) is replaced by H2O(l), and the 2S(s) replaced with O2(g).
Blackman
measured effect that changes in light intensity, CO2 concentration, and temperature have on the rate of photosynthesis in green plants:
1. At low light intensities, the rate of photosynthesis could be increased by increasing the light intensity, but not by increasing temperature.
2. At high light intensities, the rate of photosynthesis is increased by increasing temperature, not light intensity.
Photosynthesis takes place in two stages, an initial light-dependent (photochemical) stage and a second light-independent (bio- chemical) stage that is primarily affected by heat, not light.
photosynthesis is sensitive to carbon dioxide. The overall rate of photosynthesis decreased when the concentration of carbon dioxide was lowered
Engelmen
Engelmann used Spirogyra and aer- obic bacteria to determine whether different colors of visible light carry out photosynthesis equally well. He found that the bacteria accumulated in areas where the chloroplast of Spirogyra was exposed to red and blue-violet light, indicating that these colours best support photo- synthesis, and thereby oxygen production. This is called the action spectrum for photosynthesis.
Ground state
Unexcited electron
Excitation + when does this occur in photosynthesis
Occurs when a photon is absorbed by an electron of cholorphyll.
electron gains energy and moves from its ground state to its excited state.
Antenna complex
Complex containing the pigments necessary for photosynthesis. The complex at which light is absorbed.
