Photosynthesis Flashcards
what is photosynthesis?
Photosynthesis is a metabolic pathway that converts light energy into chemical energy for synthesis of carbohydrate
What is the chemical equation for photosynthesis?
6 CO2 + 12 H2O + light ⇒ C6H12O6 + 6O2 + 6H2O
On land almost all plants are photo_________
On land almost all plants are photoautrotrophs
What is an autotroph?
sustain themselves without eating anything dervived from other living beings
What are hetertrophs?
almost all dependant on photoautotrophs for food and oxygen
autotrophs are _______
hetertrophs are _______
autotrophs are producers
hetertrophs are consumers
In aquatic enviroments algae are _________autotrophs
In aquatic enviroments algae are photoautotrophs
elysia chlorotica: light harvesting ________
elysia chlorotica: light harvesting slug
photosynthetic organisms:
- _______ plants
- multicellular ______
- _____cellular eukaryotes
- purple sulfur ________
- ________bacteria
photosynthetic organisms:
- land plants
- multicellular algae
- unicellular eukaryotes
- purple sulfur bacteria
- cyanobacteria
- all green parts of the plant have ________
- ________ are the major site of photosythesis
- _______ is what gives the green pugment, which is located within the chloroplasts
- The light energy absorbed by _______ drives the synthesis of organic molecules in the chloroplasts
- chloroplasts are found mainly in the cells of the mesophyll, the tissue in the interior of the leaf
- all green parts of the plant have chloroplasts
- Leaves are the major site of photosythesis
- chlorophyll is what gives the green pugment, which is located within the chloroplasts
- The light energy absorbed by chlorophyll drives the synthesis of organic molecules in the chloroplasts
- chloroplasts are found mainly in the cells of the mesophyll, the tissue in the interior of the leaf
Chloroplast:
- has an envelope of two _______ surrounding a thick dense fluid
- _________: thick dense fkuis in the chloroplast
- _________: are connected sacs in the chloroplasts which compose a third membrane system, may be stacke
- ________: stacked thylakoids
- ___________: the pigments which gives leaves their green colour, resides in the thylakoid membrane
Chloroplast:
- has an envelope of two membrane usrrounding a thick dense fluid
- Stroma: thick dense fkuis in the chloroplast
- Thylakoids: are connected sacs in the chloroplasts which compose a third membrane system, may be stacke
- Grana: stacked thylakoids
- Chlorophyll: the pigments which gives leaves their green colour, resides in the thylakoid membrane
Chloroplast split ________into hydrogen and oxygen, incorporationg the electrons of hydrogen into sugar molecules and releasing ________ as a biproduct.
Chloroplast split H2O into hydrogen and oxygen, incorporationg the electrons of hydrogen into sugar molecules and releasing oxygen as a biproduct.
The light reaction (photo part ) in the thylakoids consists of
- solit H2O
- Release O2
- reduce electron acceptor NADP+ to NADPH
- generate ATP from ADP by photophosphorylation
Photosynthesis is a ________ process in which CO2 is reduced
Photosynthesis is a redox process in which CO2 is reduced
What are the two sections of photosynthesis?
Light reactions (photo part)
calvin cycle (synthesis part)
The calvin cycle consists of?
The calvins cycle takes place in the stroma, forms sugar from CO2 using ATP and NADPH
The clavin cycle begins with carbon fixation incorporation CO” into organic molecules
Nature of Sunlight
- __________: light is a form of electromagnetic energy
- travels in rythmic waves
- ___________: distance between crests of the wave
- Wvaelength determines the type of electromagnetic energy
Nature of Sunlight
- electromagnetic radiation: light is a form of electromagnetic energy
- travels in rythmic waves
- Wavelength: distance between crests of the wave
- Wvaelength determines the type of electromagnetic energy
__________: is the entire range of electromagnetic energy, or radiation
_______: consists of wavelengths that produce colours we can see
________: light behaves as though it consists of discrete particles
the electromagnetic spectrum: is the entire range of electromagnetic energy, or radiation
Visible light: consists of wavelengths that produce colours we can see
Photons: light behaves as though it consists of discrete particles
Photosynthetic Pigments: The Light Receptors
- Pigments are substances that ________ visible light
- Different pigments absorb different wavelengths
- Wavelengths that are not absorbed are _______ or transmitted
- Leaves appear green because ________reflects and transmits green light
Photosynthetic Pigments: The Light Receptors
- Pigments are substances that absorb visible light
- Different pigments absorb different wavelengths
- Wavelengths that are not absorbed are reflected or transmitted
- Leaves appear green because chlorophyll reflects and transmits green light
A ________ measures a pigment’s ability to absorb various wavelengths. This machine sends light through pigments and measures the fraction of light _________at each wavelength
A spectrophotometer measures a pigment’s ability to absorb various wavelengths. This machine sends light through pigments and measures the fraction of light transmitted at each wavelength
- An ________ spectrum is a graph plotting a pigment’s light absorption versus wavelength
- The absorption spectrum of _________ a suggests that violet-blue and red light work best for photosynthesis
- An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process
- An absorption spectrum is a graph plotting a pigment’s light absorption versus wavelength
- The absorption spectrum of chlorophyll a suggests that violet-blue and red light work best for photosynthesis
- An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process
__________: Involved in photoprotection absorb light that would otherwise damage chlorophyll.
Carotenoids: Involved in photoprotection absorb light that would otherwise damage chlorophyll.
- The action spectrum of photosynthesis was first demonstrated in 1883 by Theodor W. Engelmann
- In his experiment, he exposed different segments of a filamentous ________ to different wavelengths
- Areas receiving wavelengths favorable to photosynthesis produced excess ________
- He used the growth of aerobic bacteria clustered along the alga as a measure of O2 production
- The action spectrum of photosynthesis was first demonstrated in 1883 by Theodor W. Engelmann
- In his experiment, he exposed different segments of a filamentous alga to different wavelengths
- Areas receiving wavelengths favorable to photosynthesis produced excess O2
- He used the growth of aerobic bacteria clustered along the alga as a measure of O2 production
The difference of _________- between pigments is due to structural differences between pigment molecules
The difference of absorption between pigments is due to structural differences between pigment molecules
What parts make up a chlorophyl?
porphyrin ring: light absorbing head, with a magnesium at its centre
Hydrocarbon tail: interacts with the hydrophobic regions of proteinn inside the thylakoid membranes of chloroplasts
What is a light harvesting complex?
When a chlorophyll attaches toa protein, that aids photosynthesis
- When a pigments absorbs light, it goes from a ground state to an ________ state which is unstable
- When excited electrons fall back to their grounded state, _________are often given off, and afterglow called ________
- If illuminated, an isolated solution of chlorophyll will fluoresce, giving off heat and photons
- When a pigments absirbs light, it goes from a ground state to an excited state which is unstable
- When excited electrons fall back to their grounded state, _________are often given off, and afterglow called ________
- If illuminated, an isolated solution of chlorophyll will fluoresce, giving off heat and photons
A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes
- A ___________ consists of a reaction-center complex (a type of protein complex) surrounded by light-harvesting complexes
- The ____________ (pigment molecules bound to proteins) transfer the energy of photons to the reaction center
A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes
- A photosystem consists of a reaction-center complex (a type of protein complex) surrounded by light-harvesting complexes
- The light-harvesting complexes (pigment molecules bound to proteins) transfer the energy of photons to the reaction center
Light Reactions:
- chlorophyll molecules are excited by absorbing ______ energy
- In the thylakoid membrane chlorophyll molecules are organised into _________
Light Reactions:
- chlorophyll molecules are excited by absorbing light energy
- In the thylakoid membrane chlorophyll molecules are organised into photosystems
What is a photsystem
Photosystems are functional and structural units of protein complexes involved in photosynthesis that together carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons.
How many photosystems are the thylakoids populated by and what are they called?
- photosytem II
- Photosystem I
electrons flow through the _________ when the chlorophyll pigment is excited
electrons flow through the photosystem when the chlorophyll pigment is excited
how many routes for electron flow are there in light reactions and what are they called?
- linear
- cyclic
What is linear electron flow?
Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
What are the steps of linear electron flow?
- A photon hits a pigment ans its energy is passed amoung pigment molecules until it excites P680+ (oxidising agent)
- H2O is split by enzymes, and electrons are transferred from the Hydrogen atoms to P680+ reducing it to P680
- O2 is released as a byproduct of this reaction
- each electron falls down an electron transport chain from the primary electron acceptor of PSII to PSI (P700)
- Energy Released by the fall drives the creation of a proton gradient across the thylakoid membrane
- Diffusion of H+ accross the membrane drives ATP synthesis
- Each electron falls down the STC from the primary electron acceptor of PSI to the protein ferredoxin (Fd)
- The eectrons are then transfered to NADP+
- The electron of the NADPH are available for the reactions of the calvin cycle.
What is cyclic Electron Fow?
- electrons cycle back from the Fd to the PSI reaction centre
- only uses photosystem I and produces ATP but not NADPH
- No oxygen is released
- Some organisms such as purple ______ bacteria have PS I but not PS II
- Cyclic electron flow is thought to have evolved before ______ electron flow
- Cyclic electron flow may protect cells from light-induced damage
- Some organisms such as purple sulfur bacteria have PS I but not PS II
- Cyclic electron flow is thought to have evolved before linear electron flow
- Cyclic electron flow may protect cells from light-induced damage
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria
- Chloroplasts and mitochondria generate ATP by _______, but use different sources of energy
- Mitochondria transfer chemical energy from food to ATP; chloroplasts transform _____ energy into the ______energy of ATP
- Spatial organization of chemiosmosis differs between chloroplasts and mitochondria but also shows similarities
- In mitochondria, protons are pumped to the _______ space and drive ATP synthesis as they diffuse back into the mitochondrial matrix
- In chloroplasts, protons are pumped into the ________ and drive ATP synthesis as they diffuse back into the stroma
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria
- Chloroplasts and mitochondria generate ATP by chemiosmosis, but use different sources of energy
- Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP
- Spatial organization of chemiosmosis differs between chloroplasts and mitochondria but also shows similarities
- In mitochondria, protons are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix
- In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma
ATP and NADPH are produced on the side facing the __________, where the Calvin cycle takes place
In summary, light reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH
ATP and NADPH are produced on the side facing the stroma, where the Calvin cycle takes place
In summary, light reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH
Light Reactions
2H2O + light energy ⇒ 4H+ + 4e- + O2
The 4H+ is used in the ________
The 4e- are used in the _________
O2 is released as a ___________
Light Reactions
2H2O + light energy ⇒ 4H+ + 4e- + O2
The 4H+ is used in the Proton Motive Force
The 4e- are used in the electron transport chain
O2 is released as a biproduct
where does the Calvin cycle take place?
Stroma
The Calvin Cycle uses the chemical energy of _____ and _______ to reduce CO2 to sugar
- The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle
- The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH
The Calvin Cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar
- The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle
- The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH
Calvin cycle:
- Carbon enters the cycle as _________and leaves as a sugar named _______________ (G3P)
- For net synthesis of 1 G3P, the cycle must take place three times, fixing ____________ molecules of CO2
- The Calvin cycle has three phases
- Carbon fixation (catalyzed by rubisco)
- Reduction
- Regeneration of the CO2 acceptor (RuBP)
Calvin cycle:
- Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P)
- For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2
- The Calvin cycle has three phases
- Carbon fixation (catalyzed by rubisco)
- Reduction
- Regeneration of the CO2 acceptor (RuBP)
What are the three phases of the calvin cycle?
- Carbon fixation (catalyzed by rubisco)
- Reduction
- Regeneration of the CO2 acceptor (RuBP)
What is RuBISCO?
Ribulose Bisphosphate Carboxylase- Oxygenase
Carbon fixation:
- Catalysed by _____________ (RuBISCO)
- 16% of total chloroplast protein
- Most abundant protein on the planet!
Carbon fixation:
- Catalysed by Ribulose Bisphosphate Carboxylase- Oxygenase (RuBISCO)
- 16% of total chloroplast protein
- Most abundant protein on the planet!
Photorespiration
- In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound(_____________)
- In photorespiration, rubisco adds _______ instead of ________ in the Calvin cycle, producing a two-carbon compound
- Photorespiration consumes O2 and organic fuel and releases CO2 without producing _______ or sugar
Photorespiration
- In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound(3-phosphoglycerate)
- In photorespiration, rubisco adds O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound
- Photorespiration consumes O2 and organic fuel and releases CO2 without producing ATP or sugar
C4 Plants
- C4 plants minimize the cost of photorespiration by incorporating CO2 into _______-carbon compounds
- There are two distinct types of cells in the leaves of C4 plants:
- __________ cells are arranged in tightly packed sheaths around the veins of the leaf
- _________are loosely packed between the bundle sheath and the leaf surface
C4 Plants
- C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds
- There are two distinct types of cells in the leaves of C4 plants:
- Bundle-sheath cells are arranged in tightly packed sheaths around the veins of the leaf
- Mesophyll cells are loosely packed between the bundle sheath and the leaf surface
Sugar production in C4 plants occurs in a three-step process:
- The production of the four carbon precursors is catalyzed by the enzyme PEP carboxylase in the ________ cells
- PEP carboxylase has a higher affinity for CO2 than _________ does; it can fix CO2 even when CO2 concentrations are low
- These four-carbon compounds are exported to ______ cells
- Within the bundle-sheath cells, they release CO2 that is then used in the _________cycle
Sugar production in C4 plants occurs in a three-step process:
- The production of the four carbon precursors is catalyzed by the enzyme PEP carboxylase in the mesophyll cells
- PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low
- These four-carbon compounds are exported to bundle-sheath cells
- Within the bundle-sheath cells, they release CO2 that is then used in the Calvin cycle
CAM Plants
- Some plants, including succulents, use ________ (CAM) to fix carbon
- CAM plants open their stomata at night, incorporating CO2 into organic acids
- Stomata close during the day, and CO2 is released from organic acids and used in the ______________
CAM Plants
- Some plants, including succulents, use crassulacean acid metabolism (CAM) to fix carbon
- CAM plants open their stomata at night, incorporating CO2 into organic acids
- Stomata close during the day, and CO2 is released from organic acids and used in the Calvin cycle
C4 plants have a ________ seperation of steps whereas CAM plants have a ________ seperation of steps.
C4 plants have a spatial seperation of steps whereas CAM plants have a Temporal seperation of steps.
