Term
| What percent of the sun's energy incident on a leaf is transferred to carbohydrates? |
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Definition
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Term
| Where do the light reactions occur? |
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Definition
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Term
| What are photosystems? What do they do? |
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Definition
- clusters of photosynthetic pigments in the thylakoid membranes
- absorb particular wavelengths of light |
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Term
| What was believed in ancient times? |
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Definition
| plant gets all its food from soil |
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Term
State what happened during the following dates:
1600s, 1771, 1796, 1930, 1938, 1905 |
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Definition
1600s - Belgian physician Helmont
- absorption of water causes growth of plant
1771 - English scientist Joseph Priestly: plants release gas
1796 - Dutch doctor Ingerhousz
- oxygen gas released by plants
- source of carbon in plants is carbon dioxide
- sunlight is essential
- thought oxygen was from carbon dioxide
1930 - American Van Neil
- oxygen is from the splitting of the water molecule
1938 - Van Neil
- findings are confirmed by a radioisotope of oxygen (O18) in the H2O)
1905 - Blackmen
- effects of light intensity
- carbon dioxide concentration
- temperature rate of photosynthesis in green plants |
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Term
| What are the results of the photosynthetic research through these years? |
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Definition
- in very low light & in bright light: increasing temperature does not affect photosynthesis rate
- given the same light intensity and temperature: carbon dioxide concentration varies directly with the photosynthesis rate |
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Term
Who is Engelmann?
What did he do? |
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Definition
- German botanist
- used the alga spirogyra to determine whether all colours of the visible light are used by photosynthesis equally well |
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Term
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Definition
- long and filamentous
- has a long spiral chloroplast along its length |
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Term
| What special tool did Engelmann use? For what purpose? |
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Definition
triangular prism between light and stage of microscope
white light is split into its component wavelengths |
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Term
| What happened to the spirogyra? |
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Definition
| chloroplast spread across the field of the microscope, exposed to different wavelengths of light |
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Term
| What did Engelmann add? Why? |
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Definition
aerobic bacteria to the slide
he knew that the bacteria will accumulate where there is oxygen (by product of photosynthesis) |
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Term
| What were the results of Engelmann's experiment? |
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Definition
- bacteria accumulated where there was red and blue violet light
- very few bacteria in green light |
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Term
| Why does chlorophyll appear green under normal conditions? What are considered normal conditions? |
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Definition
absorbs blue-violet & red light
white light |
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Term
| What does chlorophyll a do? |
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Definition
| transfers energy to carbon fixation reactions |
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Term
| What does chlorophyll b do? |
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Definition
| an accessory pigment i.e. it absorbs pigments that chlorophyll a absorbs poorly or not at all |
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Term
What are carotenoids?
What is an example?
What is its appearance? |
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Definition
- accessory pigments
e.g. β carotene
- absorbs blue violet light → appears yellow/orange |
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Term
| What can carotenoids absorb? Why is this important? |
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Definition
| can absorb the light wavelengths (that can damage chlorophyll) & release it as heat |
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Term
| What can carotenoids make? Why is this important? |
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Definition
| vitamin A → makes rhodopsin, a photopigment in the retina → helps low-light vision |
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Term
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Definition
| light harvesting units of chloroplasts |
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Term
| What do photosystems consist of? |
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Definition
- chlorophyll
- accessory pigments associated with proteins in clusters embedded in the thylakoid membrane |
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Term
| How many kinds of photosystems are there? What do they all have? |
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Definition
| 2; antenna complex & reaction centre |
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Term
| What do antenna complexes consist of? |
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Definition
| a number of chlorophyll molecules and accessory pigments set in a protein matrix in the thylakoid membrane |
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Term
| What do antenna complexes do? |
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Definition
| absorbs a photon of light and transfers the energy (in the form of electrons) from pigment to pigment until it reaches chlorophyll a in the reaction centre |
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Term
| What is a reaction centre? |
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Definition
| a transmembrane protein complex that contains chlorophyll a, whose electrons absorb light energy |
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Term
| What happens in the reaction centre? |
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Definition
| an e- of the chlorophyll a molecule → raised to a high energy level → transferred to the primary e- acceptor via a redox reaction; thus chlorophyll a is oxidized |
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Term
| Why do plants use photosystems I & II? |
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Definition
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Term
| What is the result of producing ATP & NADPH? |
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Definition
| water is split and oxygen is released |
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Term
What excites the e- of P680 (II)?
What happens to this excited e-? How many times does this occur? |
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Definition
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Term
| What splits water into oxygen protons and electrons? |
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Definition
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Term
| How many of those e- replace those lost by P680? |
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Definition
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Term
| What happens to the O in the chloroplast? H+? |
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Definition
| oxygen leaves the chloroplast; H+ remain inside the thylakoid space |
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Term
Where does the e- go after O leaves chloroplast? What happens here?
What does it create? |
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Definition
pass through the Q cycle
H+ is actively pumped into the thylakoid space from the stoma
an electrochemical gradient |
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Term
| How is ATP made from ADP? What is required? |
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Definition
through chemiosmosis
phosphorylation because light is required to to establish the proton gradient |
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Term
| What eventually happens to the e-? |
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Definition
| replace the ones lost by photosystem I |
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Term
What happens to the excited e- from photosystem I?
What is important about the product? |
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Definition
| passes through a different ETC and move to NADP reductase → uses 2 e- and H+ to reduce NADP+ to NADPH - needed for carbon fixation |
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Term
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Definition
- e- flow from water and end up in NADPH
- result with ATP and NADPH, both are needed for carbon fixation (the next step) |
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