Chapter Ten Flashcards
What is light energy?
it can be kinetic or potential, and is electromagnetic radiation stored as photons.
What is electromagnetic radiation?
radiation propagated as waves and particles
the amount of energy in the wave is inversely proportional to wavelength (small wavelength -> greater energy)
What is a photon?
they are packets that store energy, (particles of light)
What does absorbed energy do?
- absorbed energy adds energy to the molecule (makes it excited)
it boosts an electron in the molecule into a shell farther from the nucleus which makes it more unstable and reactive
What do pigments do with the sun’s light?
they absorb specific wavelengths in the visible range
the other light / wavelengths are scattered or transmitted which imparts the colors we see
Explain what are absorbed wavelengths.
Light can be absorbed only in certain wavelengths and it all depends on the PIGMENT
chlorophyll a and b absorb red and blue wavelengths
carotenoids absorb blue and violet
Only absorbed light is useful for photsynthesis
Explain the reflected wavelengths.
Hardly no wavelength is absorbed from 500-625
No pigment absorbs pure green light, so it is reflected, which is why we perceive leaves to be green
What is the importance of photosynthesis?
The primary function / importance of photosynthesis is to convert solar energy into chemical energy and then store that chemical energy for future use, but it also makes oxygen as a byproduct.
Without photosynthesis, cellular respiration wouldn’t have a hope in functioning i.e it sustains all the food chains in an ecosystem
What is the general reaction of photosynthesis?
6 H2O + 6 CO2 through use of light energy -> C6H12O6 + 6 O2
Water + Carbon Dioxide in the presence of light YIELD Glucose and Oxygen gas
What are the two pathways of photosynthesis?
- Light reactions (dependent)
- Carbon fixation (light independent) Calvin Cycle
What is the input and output of light reactions?
Input: Sunlight, 6H2O, ADP, Pi, NADP+
Output: 6 O2, ATP, NADPH
What is the input and output of the carbon fixation (light independent reactions?)
Input: 6 CO2, 12 NADPH, 18ATP
Output: 2 G3P (can form one glucose), 12 NADP+, 18 ADP, and 18 Pi
How are the light dependent reactions connected to the carbon fixation reactions?
The ATP and NADPH made in the light dependent reactions are used in the carbon fixation reactions
What are photosystems?
multi-protein light harvesting complexes embedded in the thylakoid membrane
they contain pigment molecules, like chlorophyl that absorb the photon and make the molecule excited.
In which pathway are photosystems used?
They are used in the light dependent reactions
Explain light harvesting complexes and reaction centers.
When a pigment molecule absorbs a photon, the molecule becomes unstable and the energy is released quickly, so the energy is absorbed by other pigment molecules and is passed to the reaction centers, where it is converted to chemical energy (when the excited molecule gives up an electron to the electron acceptor
Chlorophyll in the reaction center is oxidized
The electron acceptor molecule is reduced
Explain the orientation of the light harvesting complexes and reaction centers.
A protein complex that includes chlorophyll molecules and carotenoid molecules make up the antenna system (light harvesting complex)
Inside the antenna system there are different proteins that contain other chlorophylls
This entire thing is embedded in the thylakoid membrane
What is light energy converted to and what is the final electron acceptor in the photosystems?
The light energy is converted into chemical energy in the form of potential energy.
The electron acceptor in the photosystem is only the first of many
*The final electron acceptor is NADP+
What photosystems are used in noncyclic electron transport?
Photosystem II - when an chlorophyll gives up its excited electron it is unstable and grabs another electron from water, and the water becomes oxidized (the H+ are dropped in the thylakoid place)
The electron is passed through an ETC which pumps H+ into the thylakoid space by using the energy of the electron and ATP synthase eventually synthesizes
Photosystem I - chlorophyll takes an electron from the last carrier in PS2 and the excited electron is passed through several other carriers and reduces NADP+ to NADPH
What photosystems are used in cyclic electron transport?
Photosystem I - when the chlorophyll gives up its excited electron, the energetic electron then passes through the ETC which pumps H+ into the thylakoid space by using the energy of the electron and then ATP synthase does its thing phosphorylate ADP
The electron is then accepted by the chlorophyll again and the process re-starts
How is ATP produced during light dependent reactions?
It is formed by photophosphorylation,
when H+ flows back across the membrane from the lumen to the stroma through ATP synthase in the thylakoid membrane, it uses that energy to synthesize ATP
What two things contribute to the H+ gradient?
Hint: (ones in the lumen and ones in the stroma)
Water oxidation in the lumen and NADP+ reduction in the stroma
Why is ATP synthase important?
If ATP synthase isn’t woking correctly, the H+ concentration will just keep building up potential energy but there will no way to release it.
The ATP produced in the light dependent reactions is needed for the light independent reactions
What is CO2 reduced to in the light independent (carbon fixation) reactions and where does the energy come from to do this?
it is reduced to carbohydrates, and it uses the energy stored as potential energy in ATP and NADPH
Where do the carbon fixations occur?
they occur in the stroma
What enzyme is involved in the Calvin Cycle?
Rubisco
For every turn of the Calvin Cycle, what happens?
One CO2 is fixed and One RuBP is regenerated
What is photorespiration?
It is when RuBP reacts with O2 in the Calvin Cycle instead of CO2
it consumes O2 and releases O2, and it happens only in night
it wastes ATP and NADPH and reduces the net carbon fixed by the Calvin cycle
How do C4 and CAM plants avoid photorespiration?
C4 plants they have physically separated the Calvin Cycle (mesophyll and bundle sheath cells) from O2 rich spaces in the leaf, so the rubisco always encounters high CO2
CAM plants only open their stomata at night
What are some examples of energy loses in photosynthesis?
- Wavelengths that couldn’t be absorbed - 50%
- Light energy not absorbed due to plant structure - 30%
- Inefficiency of light reactions 10%
- Inefficiency of CO2 fixation pathways 5%
