Photosynthesis

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Word equation for photosynthesis?
Carbon dioxide + water > Oxygen + Glucose (+energy)
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What is photosynthesis?
A physiological process that converts light energy into chemical energy. This chemical energy is then used by organisms to synthesis organic molecules from inorganic ones.
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Why are organic molecules important?
They form the building block of living cells
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What living organisms do photosynthesis?
Plants, algae and some bacteria
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What is autotrophic nutrition?
Type of nutrition where organic molecules (e.g. carbohydrates) are synthesised from inorganic ones, using chemical energy
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Define photoautotroph
An organism that uses light (as a source of autotrophic nutrition) to synthesise complex organic molecules from inorganic ones e.g. water + carbon dioxide
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Why are plants producers/at the first trophic level of the food chain?
They provide the energy and organic molecules for non-photosynthetic organism
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Why is photosynthesis an example of carbon fixation?
Because it involves the incorporation of cabon molecules (from CO2) to make sugar
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What is the main product of photosynthesis?
Glucose (monosaccharide)
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What type of process is carbon fixation?
An endothermic (requires energy) + reduction (involves the gain of electrons)
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What organisms repsire?
Plants + other organisms that photosynthesise & animals
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Why is respiration an oxidation process?
It involves the loss of electron: organic molecules are oxidised to release chemical energy to form ATP
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Why is respiration an exothermic reaction?
Because chemical energy is released
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Define the term heterotroph?
An organism that digests complex organic molecules and uses the smaller ones as respiratory substrates, to release chemical potential energy
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Word equation for respiration?
Oxygen + Glucose > Carbon dioxide + water
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How do photosynthesis and respiration interrelate?
The products of one are the raw products of the other
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When does photosynthesis occur in plants/alage/bacteria?
In the presence of sufficient light intensity (during the day)
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When does respiration occur in living organisms?
All the time
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What is compensation point?
When photosynthesis + repsiration are occuring at the same rate, so there's no net loss or gain of carbohydrate
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What 3 membranes exist in chloroplasts?
Inner, outer, and thylakoid
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What are the 3 compartments of a chloroplast?
Thylakoid lumen, intermembrance space, stroma
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What is the purpose of fat droplets?
Act as reserves of raw material for the synthesis of new membranes
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What are grana?
Stacks of up to 100 thylakoid membranes (linked to adjacent granum by intergranal lamellae)
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What is purpose of the grana?
To provide a large surface area for the attachment of photosystems, ATP Synthase + electron carriers
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What are grana surrounded by, and what is the benefit of this?
Stroma- close contact allows the products of light-dependent stage to easily pass into the stroma for the light-independent stage
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What is the stroma?
Fluid-filled matrix
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What does the stroma contain?
Enzymes for the light-dependent stage, starch grains, oil droplets, small ribosomes + loop of DNA
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Purpose of the loop of DNA?
Contains genes that code for the proteins needed for photosynthesis (e.g. enzymes)
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Where are the proteins assembled?
At the chloroplasts ribosomes
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What is a photon?
Particle of light (a quantum of energy)
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What is a photosystem?
A funnel shaped structure in thylakoid membranes, containing primary and acessory pigments for the harvesting of light
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Function of photosystems?
To harvest light energy, which is then funnelled down to the primary reaction centre
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What are photosynthetic pigments?
Pigments that absorb (+ reflect) specfic wavelengths of light and transfer the energy down to the primary pigment reaction centre
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Examples of photosnythetic pigments?
Chlorophyll a + b, carotenoids & xanthophylls
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What is chlorophyll a?
The primary pigment reaction centre, that appears blue-green and absorbs red light/some blue
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What is the primary reaction centre?
A molecule of chlorophyll A
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What are the 2 types of chlorophyll a?
P680 (PSII) + P700 (PSI)
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What do accessory pigments consist of?
Chlorophyll b and caternoids
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Moleclar structure of all different types of chlorophylls?
A porphyrin group containing a Mg atom and long hydrocarbon chain
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What happens in a photosystem?
A photon strikes + is absorbed by an acessory pigment. It's electrons become excited and the energy is passed down to the primary reaction centre
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What happens to the glucose made in photosynthesis?
It is converted into sucrose (for translocation), then starch (good energy storage)
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Where does the light-depedent stage occur?
In the thylakoid membrane
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What is photolysis?
The splitting of water using light, producing hydrogen, electrons and oxygen
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What is photophosphorylation?
The formation of ATP from ADP and Pi, in the presence of light
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What photosystem/s is involved with non-cyclic photophosphorylation?
PSII and PSI
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What photosystem/s is involved with cyclic photophosphorylation?
PSI
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What is the peak absorption of red light in PSI + PSII?
PSI= P700 & PSII= P680
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What are the products of non-cyclic photophosphorylation?
ATP, oxygen + reduced NADP
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What is the product of cyclic photophosphorylation?
ATP in smaller quantities
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What is the electron transport system?
Chain of electron carriers that accept then donate electrons to the next carrier, becoming reduced then reoxidised in the process
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What pumps protons across the thylakoid membrane into the thylakoid lumen?
Energy released from the electron transport chain
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What is ferrodoxin?
A protein-iron-sulfur complex
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What does ferrodoxin do?
Accepts the electrons from PSI and donates them to NADP in the stroma
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What finally the accepts the H+ ions (protons)?
NADP- becoming reduced (NADPH)
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What do guard cells do with ATP generated by PSI?
They use it to actively transport K+ ions into the cell, lowering the water potential, so water flows in by osmosis. This causes the stoma to open.
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Where does the light-indepedent stage (calvin cycle) occur?
In the stroma
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Why is the calvin cycle 'carbon fixation'?
It involves the incorporation of carbon (from CO2) into organic compounds
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What is carbon dixoide's role?
It is the source of carbon for the synthesis of all organic molecules
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How does carbon dioxide enter the leaf?
It enters through the stomata diffuses through the spongy mesophyll layer to the palisade layer then into the palisade cells
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Why is a concentration gradient maintained?
Because carbon fixation is occuring in the stroma
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The calvin cycle doesn't directly use light, but why does it only run in the daytime?
Because it uses the products of the light-dependent stage; NADPH + ATP
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What is the role of hydrogen atoms from NADPH and ATP?
H atoms reduce GP to TP, using energy from ATP
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What is RuBP?
Ribose biphosphate (5C carbon acceptor)
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1st step of calvin cylce?
RuBP (5C) combines with carbon dioxide (becoming carboxylted), catalysed by rubisco
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2nd step?
An unstable intermediate 6C compound formed, breaks down immediately into 2 molecules of GP
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What is formed?
2 molecules of glycerate-3-phosphate
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3rd step?
Using H from NADP, the 2 molecules of GP are reduced to TP using energy from ATP
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What is TP?
Triose phosphate
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At what rate is ATP used?
2 molecules of ATP per every carbon dioxide fixed
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What happens to 10 out of 12 TP molecules generated?
There atoms are rearranged to regenerate 6 molecules of ribose biphosphate (RuBP). This requires phosphate groups.
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How many turns of the cycle is needed to produce 2 molecules of TP + single molecule of glucose
6 turns
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What is the net product of the calvin cycle?
2 Molecules of TP
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What is the fate of TP?
Used to synthesise glucose (converted into sucrose, starch + cellulose)
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What happens to glucose otherwise?
Its used to make amino acids, fatty acids and glycerol (that can be respired)
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What factors affect photosynthesis?
Light intensity, water availlability, CO2 concentration, temperature, availability of chlorophyll, electron carriers, enzymes + ATP synthase
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What is a limiting factor?
A factor present in these least favourable amount
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Other cards in this set

Card 2

Front

What is photosynthesis?

Back

A physiological process that converts light energy into chemical energy. This chemical energy is then used by organisms to synthesis organic molecules from inorganic ones.

Card 3

Front

Why are organic molecules important?

Back

Preview of the front of card 3

Card 4

Front

What living organisms do photosynthesis?

Back

Preview of the front of card 4

Card 5

Front

What is autotrophic nutrition?

Back

Preview of the front of card 5
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