Photosynthesis: Light Reactions - 4 Flashcards
What is absorbed, released, and created by plants in photosynthesis
plants use light energy from the sun to create carbohydrates stored in plants from carbon dioxide and water while releasing oxygen as a by-product
What is the most photosynthetically active tissue in plants
mesophyll of leaves
Define mesophyll
inner tissue of leaves that contain chloroplasts, which contain light-absorbing green pigments, the chlorophylls
What are the 3 major steps of photosynthesis
- absorb light (requires pigment system)
- transfer of electrons away from the excited pigment (results in 3 things)
- atmospheric CO2 converted to carbs using ATP and NADPH
In the second step of photosynthesis when electrons are transfered away from the excited pigment molecule, what 3 things can be done with that electron
- used for ATP synthesis
- used in NADPH formation
- O2 evolution
Where is the site of photosynthesis
chloroplasts
How many membranes does a chloroplast have
2, inner and outer
Define thylakoid membrane
separates the 2 compartments inside the chloroplast (lumen and stroma)
define lumen
inside the thylakoid membrane
define stroma
outside the thylakoid membrane
Light has characteristics of both ____ and _____
light and wave
What three things can results from light-energized chlorophyll
- fluoresce
- transfer energy to another molecule
- use its energy to drive chemical reactions
what wavelengths are shorter than visible light and what are longer
shorter = ultraviolet
longer = infrared
what is sunlight made of
photons of different wavelengths
Define absorption spectrum
provides information about what light energy is absorbed by a molecule or substance based on the wavelength of the light
absorption spectrums are determined by a
spectrophotometer, by non-absorbing solvents
what wavelengths are absorbed by chlorophyll
400nm-700nm
why does chlorophyll appear to be green
because it strongly absorbs red and blue light
what occurs when a molecule of chlorophyll absorbs a photon
it transitions into a higher energy level, excited state
What happens to the chlorophylls state when in a higher excited state
it is unstable and rapidly gives up some energy to its surroundings as heat, then enters the lowest excited state for a short time
What are the 4 pathways for disposing excited chlorophylls available energy
- Fluorescence (emit a photon)
- release as heat only
- energy transfer (transfers its energy to another molecule)
- photochemistry (chemical reaction occurs)
what chlorophylls are abundant in green plants and which are found in some protists and cyanobacteria
a and b
c, d, and f
Besides chlorophylls, what are the 3 other main pigments that participate in photosynthesis
carotenoids, bacteriochlorophylls, and billin pigments
Define structure of carotenoids
linear molecules with multiple conjugate double bonds that transfer electrons to chlorophylls for photosynthesis. they are accessory pigments that absorb 400-500nm (therefore orange)
Explain the molecular structure of chlorophylls
complex ring structure that contain Mg at the centre with surrounding Ns both for light absorption. Contain long hydrocarbon tail
What is the purpose of the hydrocarbon tail of chlorophylls
anchors the chlorophyll to the hydrophobic portion of the environment
What differs between chlorophyll a and b in their ring structure
a = CH3
b = CHO
Define action spectrum
a graphic representation of magnitude of biological effectiveness to different wavelengths of light