Photosynthesis

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What is the absorption spectrum?
The light absorbed by the photosynthetic pigments at different wavelengths
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How are the electrons and ions used from splitting water used in the light-dependent stage?
-The electrons are used to replace those emitted from PSII
-The H+ ions combine with electrons to reduce NADP to NADPH
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What is an advantage of having 2 Photosystems?
They can harvest a greater range of wavelengths of light
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How are the products of the light-dependent stage used?
-NADPH is used to reduce GP to form TP, with energy provided by ATP
-The phosphate from ATP is used to convert RuP to RuBP
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Why might chloroplasts change orientation?
In very high light intensities, so as to avoid heat damage
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What are ATP's distinct roles in the light independent reaction?
1. Provide energy for the conversion of GP to TP
2. Provides a phosphate to convert RuP to RuBP
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If CO2 is removed, what happens to GP and RuBP?
-When CO2 is no longer available it cannot be 'fixed' and combined with RuBP
∴ conc. of GP falls as it is converted to TP and not replaced
-conc. of RuBP builds as still being replaced but no CO2 to 'fix'
-conc. of both levels off as all reactions of ligh
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Why would increasing 1 factor eg. enzyme conc. not be enough to speed up photosynthetic rate?
'if any environmental factor is limiting then increasing other factors will have little/no effect'
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What does 'metabolically expensive' mean?
Requiring high rates of respiration
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Explain the link between the two stages of photosynthesis.
The light independent stage is dependent on the light-dependent stage for ATP and NADPH
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Why is 'light independent' a more accurate name than the 'dark stage'?
It doesn't require direct light, but it does require the products of the light dependent stage, ATP and NADPH, to convert GP to TP.
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In Calvin's exp, why does the number of radioactive compounds increase up to a point and then level off?
More time allows additional compounds in the light-independent stage to become labelled, until eventually all compounds are labelled, as there is a finite no. of compounds produced
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Why did Calvin only increase the time interval by a few seconds each time?
If the time interval was longer the sequence of molecules could not be worked out, as groups of compounds would be labelled. The reaction is rapid due to being catalysed by the enzyme Rubisco
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What does Rubisco stand for?
Ribulose Bisphosphate Carboxylase
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Why did Calvin use a 'lollipop flask'?
-To reduce the effect of shading, so maximising the amount of light getting to the chorella
-Ensures all chorella p'syning at the same rate
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Why would chromatograms of the same types of leaves differ at different times of the year?
There is a reduced concentration of pigments in the later months, as pigments are broken down, and some withdrawn back into the tree
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What variables should be controlled when doing leaf chromatography?
-Should be taken from the same part of the tree eg. same position on same branch to reduce
effect of varying light intensity
-Same no. of spots added fro each pigment to control conc. of spot
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How would scientists measure p'syn?
-use water plant eg. elodea
-use apparatus to collect O2 produced over time in different environmental conditions, eg. Audus Apparatus or Manometer
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How do you know a graph is showing net p'syn as opposed to gross p'syn?
The graph shows the influence of respiration
-Some negative values are present ∴ CO2 output is indicated
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Other cards in this set

Card 2

Front

How are the electrons and ions used from splitting water used in the light-dependent stage?

Back

-The electrons are used to replace those emitted from PSII
-The H+ ions combine with electrons to reduce NADP to NADPH

Card 3

Front

What is an advantage of having 2 Photosystems?

Back

Preview of the front of card 3

Card 4

Front

How are the products of the light-dependent stage used?

Back

Preview of the front of card 4

Card 5

Front

Why might chloroplasts change orientation?

Back

Preview of the front of card 5
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