Term
| Where are photosynthates produced? |
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Definition
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Term
| What is the main photosynthetic tissue in a leaf? |
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Definition
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Term
| Give 3 adaptations of the leaf for photosynthesis. |
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Definition
- Chloroplasts
- Air spaces to allow diffusion of gases
- Densely packed palisade layer |
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Term
| Why are compartment reactions important? |
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Definition
- Reaction can occur in small volume
- Membranes isolate reactions within organelles
- Mitochondria can be positioned close to areas needing ATP |
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Term
| Where does the light dependent stage occur? |
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Definition
| Thylakoid membrane and thylakoid space of chloroplast |
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Term
| Where does the light independent stage occur? |
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Definition
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Term
| Where are photosynthetic pigments found? |
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Definition
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Term
| What is the role of photosynthetic pigments? |
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Definition
| Capture light energy and convert it into chemical energy |
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Term
| What are the two main types of photosynthetic pigments? |
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Definition
- Primary pigments
- Accessory pigments |
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Term
| What wavelength is absorbed by primary pigments? |
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Definition
| Chlorophyll a - blue and red |
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Term
| What wavelength is absorbed by accessory pigments? |
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Definition
- Chlorophyll b = blue and red
- Carotenoids (xanthophyll & carotene) = violet/blue |
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Term
| Why are accessory pigments important? |
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Definition
| They absorb wavelength of light not absorbed by primary pigments which allows a wider range of wavelengths to be absorbed |
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Term
| Which macronutrient is needed to produce chlorophyll a? |
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Definition
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Term
| Why do we add acetone for chromotography? |
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Definition
| Dissolve the phospholipids membranes to extract the pigments |
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Term
| Why do we need a solvent for chromotography? |
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Definition
| Dissolve the solute and carry pigment up the chromatography paper |
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Term
| Why do pigments travel different distances? |
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Definition
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Term
| What is the absorption spectrum? |
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Definition
| A graph that shows the amount of light absorbed by pigments at each wavelength of light |
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Term
| Little would be absorbed where? |
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Definition
| Where the green light is reflected |
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Term
Specify the wavelength and colour absorbed by each pigment.
- Chlorophyll a
- Chlorophyll b
- Carotenoid |
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Definition
Chlorophyll a - 425-675 blue and red
Chlorophyll b - 450-640 blue and orange
Carotenoid - 475 blue |
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Term
| What does an action spectrum show? |
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Definition
| A graph that shows the rate of photosynthesis at different wavelengths of light |
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Term
| Where are photosystems found? |
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Definition
| On the thylakoid membrane |
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Term
| What is the role of photosystems? |
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Definition
- Absorb photons of light
- Act as transducers, transferring light energy to high energy electrons which is used to fuel proton pumps and synthesise ATP |
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Term
| What is an antenna complex? |
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Definition
| Accessory pigments grouped into clusters with associated proteins |
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Term
| What happens once the photons of light reach chlorophyll a? |
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Definition
| Electrons are excited to become high energy electrons |
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Term
| What are the two photosystems involved in light dependent reaction? |
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Definition
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Term
| Does light dependent reaction require light? |
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Definition
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Term
| Where does the light dependent stage occurs? |
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Definition
| Thylakoid membranes and thylakoid space |
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Term
| What is synthesised during light dependent stage? |
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Definition
| ATP vis photophosphorylation |
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Term
| Is NADP reduced or oxidised? |
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Definition
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Term
| What does the light dependent reaction release? |
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Definition
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Term
| What are the two light dependent reactions? |
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Definition
- Non-cyclic photophosphorylation
- Cyclic photophosphorylation |
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Term
| Why might some light hit not be used in photosynthesis? |
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Definition
- Reflected
- Transmitted - not hit chloroplast
- Wrong wavelength |
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Term
Explain the non-cyclic photophosphorylation?
(Keywords: 2 e-, higher energy level, electron acceptors, chain of carriers, PSI, pump protons, electrochemical gradient, proton gradient, ATP synthase, ATP from ADP + Pi, PSI, reduce NADP to NADPH, maintain electrochemical gradient, non-cyclic photophosphorylation |
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Definition
-Photons of light absorbed by PSII
-Passed to chlorophyll a in the reaction centre
-This excites 2 e- to a higher energy level
-passed to e- acceptors
-transferred along a chain of carriers to PSI
-which releases energy
-used to pump protons from stroma in thylakoid space
-Forms an electrochemical gradient due to high concentration of H+
-Protons flow down the proton gradient through proton channel connected to ATP synthase
-Provides energy for formation of ATP
-PSI
-Photons of light absorbed
-two e- raised to higher energy level
-passed to electron acceptor
-tranfers electrons to protons into the stroma
-which then reduces NADP to NADPH
-Use of H+ to reduce NADP lowers concentration in stroma
-maintains the electrochemical gradient
-E- do not return to their original source (non cyclic) |
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Term
| Suggest the effect of the high concentration of H+ ions in the thylakoid space. |
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Definition
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Term
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Definition
| Splitting of water using light |
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Term
| What are the products of photolysis? |
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Definition
| Water splits into O2, protons and e- |
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Term
| Where does cyclic photophosphorylation occur? |
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Definition
| In bacteria and primitive plants |
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Term
| When is cyclic photophosphorylation used in plants? |
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Definition
| When they need extra ATP and CO2 is in short supply or levels of reduced NADP are very high |
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Term
| Which photosystem is involved in cyclic photophosphorylation? |
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Definition
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Term
| Describe the process of cyclic photophosphorylation. |
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Definition
-Light energy is absorbed at PSI and channeled to chlorophyll a
-e- become excited, energised and released
-They are accepted bu an e- acceptor
-and passed along the same transfer chain as that used by the e- from PSII
-Protons are pumped into the thylakoid space and ATP is produced
-Via chemiosmosis
-The e- are excited and released from PSI return to PSI |
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Term
| Does the light independent stage require light? |
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Definition
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Term
| What is the role of light independent stage? |
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Definition
| It uses ATP and NADPH from light dependent stage to fix CO2 into organic molecules |
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Term
| Where does the light independent stage occur? |
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Definition
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Term
| Explain the light independent stage |
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Definition
-CO2 is fixed with RuBP
-The enzyme RuBisCo catalyses this reaction
-Forms an unstable 6C compound which splits into two glycerate 3 phosphate
-Reduced using NADPH produced during light dependent stage
-ATP is hydrolysed and the phosphate is transferred to glycerate 3 phosphate to from triose phosphate
-One C atom of the 6 can be used to produce organic molecules such as glucose
-the remaining 5 are used to regenerate RuBP |
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Term
What does deficiency of___causes?
Nitrates
Mg2+
PO42- |
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Definition
NO3- - chlorosis- yellowing leaves due to inadequate chlorophyll production so plant no longer able to absorb light energy
-Reduced growth of organs
Mg2+
-Pronounced chlorosis between veins of older leaves as existing Mg2+ is moved and transported to new leaves
PO42-
-Stunting of plant growth |
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Term
| How does temperature affect the rate of photosynthesis? |
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Definition
| As temperature increases so does the rate of photosynthesis and enzyme activity |
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Term
| Describe the effect of enzyme denaturation on the rate of photosynthesis |
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Definition
| Active site changes shape therefore is no longer complementary to its substrate, no ESC form and rate of reaction slows down |
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Term
| Suggest why an increase in temperature speeds up the rate of light independent stage more than light dependent stage. |
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Definition
| Light dependent stage is less dependent on enzyme activity |
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Term
| Explain the implications of the fact thay light dependent stage is less dependent on enzyme activity |
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Definition
| Increase in temperature speeds up the LIS more than LDS. The supply of products from the LDS (ATP & NADPH) will not be able to keep up with the demand from the LIS. Overall rate of photosynthesis will become limited by supply |
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Term
| How does CO2 affect rate of photosynthesis? |
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Definition
Concentration often limits the rate of photosynthesis
-Overall as CO2 conc. + so does the rate of photosynthesis |
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Term
| How does light intensity affect rate of photosynthesis? |
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Definition
| As light intensity increases so does the rate of non-cyclic photophosphorylation. |
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