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self feeders; sustain themselves w/o eating anything derived from other organisms; producers; ultimate source of organic compounds
autotrophs
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live on compounds produced by other organisms; consumers; dependent on photosynthesis for both food and oxygen
heterotrophs
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What is the equation for photosynthesis?
6CO2 +6H2O + Light Energy ----> C6H12O6+ 6 O2
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How do we know that oxygen released by photosynthesis comes from water.
It was used to follow the fate of the oxygen atoms during photosynthesis. Experiments showed that O2 from plants was labeled with oxygen-18 only if water was the source of the tracer. If oxygen- 18 was introduced to the plant in the form of CO2, the label did not turn up in the released O2.
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__ is not a single process, but two processes, each with multiple steps.
photosynthesis
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Light reactions take place in the __, convert __ energy to __ energy of __ and __. It splits __ and releases O2 as a byproduct.
- thylakoid membrane
- light
- chemical
- ATP
- NADPH
- H2O
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The Calvin Cycle takes place in the __, uses __ and __ to convert CO2 to the sugar __. It returns __, __, and __ to the light reactions.
- stroma
- ATP
- NADPH
- G3P
- ADP
- inorganic phosphate
- NADP+
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SOme of the types of energy in the __ will be familiar, such as X-Rays, microwaves, and radio waves. The most important part of the spectrum in photosynthesis is ___.
What are these colors?
- electromagnetic spectrum
- visible light (visible spectrum)
- ROY. G. BIV
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Explain the relationship between wavelength and energy.
The shorter the wavelength, the more energy each photon has.
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Explain the correlation between an absorption spectrum and an action spectrum.
They both reveal which wavelengths of light are photosynthetically important.
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a graph plotting a pigment's light absorption versus wavelength. It provides clues to the effectiveness of dif. wavelengths for driving photosynthesis.
absorption spectrum
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This graphs the effectiveness of different wavelengths of light in driving photosynthesis.
action spectrum
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The __ provides clues to the effectiveness of dif. wavelengths for dirving photosnthesis, and this is confirmed by the __ which graphs the effectiveness of dif. wavelengths of light in driving photosynthesis.
- absorption spectrum
- action spectrum
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A __ is composed of a protein complex called a ___-___ complex surrounded by several ___-___ complexes.
- photosystem
- reaction-center
- light-harvesting
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Explain what part of the photosystem is involved.
complex of proteins associated with a special pair of chlorophyll a molecules a primary electron acceptor located centrally in photosystem; triggers light reactions of photosynthesis. Excited by light energy, pair of chlorophylls donate an electron to the primary electron acceptor for which passes electrons to the electron transport chain
reaction center complex
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Explain what part of the photosystem is involved.
complex of proteins associated with pigment molecules that captures light energy and transfers it to reaction-center pigments in a photosysystem (pigment molecules include chlorophyll a, chlorophyll b and carotenoids.)
light- harvesting complex
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Explain what part of the photosystem is involved.
in the thylakoid membrane of chloroplasts or in some prokaryote membranes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them
primary electron acceptor
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Photosystem I is referred to by the wavelength at which its reaction center best absorbs light, or ___; photosystem II is also known by this characteristic, or __.
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What is the source of energy that requires the electron in PS II in linear electron flow?
light
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Wha compound is the source of electrons for linear electron flow?
This compound is also the source of __ in the atmosphere.
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As electrons fall bewtween PS I and PS II, the __ uses the energy to pump __ ions. This builds a ___ that is used in chemiosmosis to produce what?
- cytochrome complex
- H+
- proton gradient
- ATP
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In PS II, the excited electron is eventually used by NADP+ reductase to join NADP+ and an H+ to form __.
NADPH
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__ is thought to be similar to the first forms of photosynthesis to evolve. In it, no water is split, there is no production of __, and there is no release of __.
- Cyclic electron flow
- NADPH
- O2
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How is chemiosmosis different in photosynthesis and cellular respiration?
- In mito. the high- energy electrons dropped down the transport chain are extracted from organic molecules, which are thus oxidized. In chloroplasts, teh electron source is water.
- Mito. uses chemiosmosis to transfer chem energy from food molecules to ATP, whereas chloroplasts transfer light energy into chem. energy in ATP
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Summarize the steps of linear electron flow into three.
- 1) Water split by photosystem II on side of membrane facing the thylakoid space.
- 2) As Pq, a mobile carrier, transfers electrons to the cytochrome complex, 4 protons are translocated across the membrane into the thylakoid space.
- 3) H+ ions removed from stroma when taken up by NADP+
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List the three places in the light reactions where a proton-motive force is generated.
- 1) H+ from water
- 2) H+ pumped across the membrane by the cytochrome complex
- 3) removal of a H+ from the stroma when NADP+ is reduced to NADPH
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As a review, note that the light reactions store chemical energy in __ and __, which shuttle their energy to the carbohydrate- producing __.
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The __ is a metabolic pathway in which each step is governed by an enzyme, much like the CAC from cellular respiration. However, keep in mind that the __ uses energy (in the form of __ and ___) and is therefore __; in contrast, cellular respiration is catabolic and releases energy that is used to generate ATP and NADPH.
- Calvin cycle
- Calvin cycle
- ATP
- NADPH
- anabolic
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The carbohydrate prodcued directly from the Calvin cycle is not glucose, but the three-carbon compound ___. Each turn of the Calvin cycle fixes one molecule of CO2; therefore, it will take __ turns of the Calvin cycle to net one __.
- glyceraldehyde-3-phosphate
- three
- G3P
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Explain the carbon fixation stage.
The Calvin cycle incorporates each CO2 molecule, one at a time, by attaching it to a 5-carbon sugar, ribose biphosphate (RuBP). The enzyme that catalyzes this step is rubisco. The product of the reaction is a 6-carbon intermediate so unstable that it immediately splits in 1/2, forming two molecules of 3-phosphoglycerate.
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The enzyme responsible for __ in the Calvin cycle, and possibly the most abundant protein on Earth, is __.
rubisco (RuBP carboxylase)
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In phase two, the __, the reducing power of __ will donate electrons to the low-energy acid __ to form the three-carbon sugar __.
- reduction stage
- NADPH
- 1,3 bisphosphoglycerate
- glyceraldehyde-3-phosphate
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The __ must be turned three times. Each turn will require a starting molecule of __, a five-carbon compound. This means we start with __ carbons distributed in __ RuBPs. After fixing three carbon dioxides using the enzyme __, the Calvin cycle forms six __ with a total of __ carbons. At this point the net gain of carbons is __, or one net __ molecule.
- Calvin cycle
- RuBP
- 15
- 5
- rubisco
- G3Ps
- 18
- 3
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How is regeneration of RuBP is accomplished?
In a complex series of reactions, the carbon skeletons of five molecules of G3P are rearranged by the last steps of the Calvin cycle into three molecules of RuBP. TO accomplish this, the cycle spends three more molecules of ATP. The RuBP is now prepared to receive CO2 again and the cycle continues.
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The net production of one G3P requires __ ATP molecules and __ NADPH molecules.
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Explain what is meant by a C3 plant.
A C3 plant is a plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a 3-carbon compound as the first stable intermediate.
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What happens when a plant undergoes photorespiration.
- Rubisco instead of binding CO2 binds O2 and forms a five- carbon product that is split into a two-carbon and a three-carbon product that peroxisomes and mitochondria fix.
- No sugar is generated.
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What is a C4 plant?
a plant in which the calvin cycle is preceded by reactions that incorporate CO2 into a 4-caron compound, teh end product of which supplies CO2 for the Calvin cycle.
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What is the role of PEP carboxylase in C4 plants?
It catalyzes the first step in the C4 pathway when CO2 is added to PEP, forming oxaloacetate.
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