bio chapter 10 - photosynthesis
What is the name of the output of the calvin cycle? glucose fructose G3P monosucrose
G3P ( glyceraldehyde 3 phosphate) -calvin cycle product is not actually glucose rather this three carbon sugar. -the calvin cycle must cycle three times to piece together one G3P, *fixing* three molecules of CO2, one per turn of the cycle.
calvin cycle step 3- regeneration of the CO2 acceptor (RuBp)
in a complex of reactions the remaining 5 G3P ( 15 carbons) are rearranged into three RuBp ( three 5 carbon sugars) to reenter the calvin cycle to start again -to accomplish this three ATPs are spent and RuBp is reassembled and ready to start the process over *three Rubp reassembled from five G3P reminding in process at the cost of 3 ATP*
cyclic electron flow
incorporates only photosystem I and is 'cyclic' -the excited electrons recycle themselves as they flow from primary electron acceptor to electron transporter Fd(ferrodoxine) through the cytochrome complex (in-between photosystem I and II) (generating ATP) and back through Pc (plastocyanine protein) back through photosystem I P700 set again. because this is not being passed to a NADP+ reductase it will not generate any NADPH. that side is effectively shut off -no release of oxygen as that would take place with photosystem II - this is the only means of generating ATP through photosynthesis for some organism
photophosyphorlation
light reactions generate ATP by using chemiosmosis to power the addition of a phosphate group to ADP
light dependent reactions vs light independent reactions
light reactions versus the calvin cycle ( light independent cycle)
stomata
microscopic pores from where gasses are able to pass into out of the plant cells
the input and outputs of light reactions phase of photosynthesis
o2 is a byproduct from the splitting of water to replace the electrons in photosystem II -In the light reactions, an enzyme is used to oxidize water (the electron donor which replaces the excited p680 electron that had been passed to the primary electron acceptor) to O2 and pass these electrons to NADP+, producing NADPH. Some light energy is used to convert ADP to ATP. The NADPH and ATP produced are subsequently used to power the sugar-producing Calvin cycle.
In mechanism, photophosphorylation is most similar to.. - oxidative phosphorylation in cellular respiration. - the Calvin cycle. - carbon fixation. - reduction of NADP+. - substrate-level phosphorylation in glycolysis.
oxidative phosphorylation in cellular respiration.
thylakoids
save which segregate the storm from the thylakoid space. -when thylakoids are are stacked in columns they are referred to grana ( granum if singular)
action spectrum
the action spectrum for photosynthesis profiles the relative effectiveness of different wavelengths of radiation in driving the process. -the effectiveness is measured by the CO2 consumption and O2 release rate
What is the biological significance of the light-independent reactions of photosynthesis? They generate ATP and NADPH. They convert ATP to sugar. They convert carbon dioxide to sugar. They make oxygen.
the convert carbon dioxide to sugar All organisms use the sugars produced by photosynthesis to generate energy.
chlorophyll
the green pigments that give leaves their color resides in the thylakoid membranes of the chloroplasts
carbon fixation
the initial incorporation of CO2 into organic material and the first step of calvin cycle
the light reactions take place in the __________ ___________while the calvin cycle occurs in the ______________ of the chloroplasts
thylakoid membrane ; stroma
C4 plants differ from C3 and CAM plants in that C4 plants _____.
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs -c4 plants are the only plants that have mesophyll and bundlesheath cells. -c4 plants fix the carbon in the mesophyll then transfer that to the bundle sheath and release an carbon to go into the calvin cycle within the bundle sheath . this is the only plant that does this
Calvin cycle has three phases. What are they in order?
Carbon fixation reduction regeneration of the CO2 acceptor
Which set of reactions uses H2O and produces O2? The light-independent reactions The light-dependent reactions
The light-dependent reactions use H2O and produce O2. The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by-product.
what is the main different between chloroplasts and mitochondria?
their method of energy. chloroplasts do not consume food to make their ATP , they use light energy. While mitochondria use chemiosmosis to transfer energy from food molecules to ATP
The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP. true or false
true
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.
cytoplasm In C4 and CAM plants carbon dioxide fixation occurs in the cytoplasm.
Which process is most directly driven by light energy? a. reduction of NADP+ molecules b. ATP synthesis c. carbon fixation in the storm d. removal of electrons from chlorophyll molecules e. creation of a pH gradient by pumping protons across the thylakoid membrane
d. removal of electrons from chlorophyll molecules? don't get this one
stroma
dense fluid that fills the empty space in chloroplasts ( similar to cytoplasm )
calvin cycle step 2; reduction
each three carbon sugar receives an additional phosphate from ATP then a pair of electrons from NADPH to change the three carbon sugar to G3P ( able to store more energy than the 3- phsphoglycerate that entered the reduction phase) (notice G3P is the same sugar that glucose is broken into in glycolysis) --for every three molecules of CO2 that enter the calvin cycle yields six G3P ( since they are combined with the 5 carbon sugar then split in half) -for ever six of these made one of the six will exit the process as a net product while the other five are required to continue the process to regenerate another three molecules of RuBp to continue the process 1 carbon enters = 2 G3P , 2nd carbon enters = 2 g3p, 3rd carbon enters = 2 g3p = total of 6 G3P from 3 CO2 molecules , one will exit as a product and the remaining 5 will have to stay in the cycle to generate more RuBp
light is a form of energy known as _____________________ energy
electromagnetic aka electromagnetic radiation - this for of energy travels in rhythmic waves -distances between the crests of the waves is called wavelength Visible light - the segment most important to life is the narrow band from about 380 nm to 750 nm in wavelength, which is the visible light that can be detected as various colors by the human eye
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
electron transport chain. even though excited electrons are transferred from photosystem II they pass through the electron transport chain which is what ultimately pumps H+ ions into the thylakoid space from the stroma creating the gradient.
for every three molecules of CO2 that enter the calvin cycle, there are six molecules of G3P formed but only one molecule of this three carbon sugar can be counted as a net gain because the rest are required to complete the cycle as it begins with 15 carbons to always have enough to form three Rubp ( 5c) molecules
facts
Which of the following products of the light reactions of photosynthesis is consumed during the Calvin cycle? The overall function of the Calvin cycle is _____.
NADPH During the Calvin cycle electrons stored in NADPH are used to reduce carbon. making sugar Using the ATP and NADPH made during the light reactions, carbon is reduced in the Calvin cycle and sugar is made.
Which term describes ATP production resulting from the capture of light energy by chlorophyll?
Photophosphorylation The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production. this takes place in the light reactions phase of photosynthesis ( phase 1)
What is the total atp and nadph used in calvin cycle?
The Calvin cycle uses 18 ATP and 12 NADPH molecules to produce one glucose molecule. or 9 ATP and 6 NADPH per one G3P molecule
Which of the following molecules is the primary product of photosystem I?
The NADPH produced by photosystem I is used to supply energy for the production of sugars during photosynthesis.
How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially
photosynthesis review 1. In the light reactions, light energy is used to oxidize H2O to O2. 2. The electrons derived from this oxidation reaction in the light reactions are used to reduce NADP+ to NADPH. 3. The Calvin cycle oxidizes the light-reactions product NADPH to NADP+. 4. The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce CO2 to G3P.
In the light reactions, light energy is used to remove electrons from (oxidize) water, producing O2 gas. These electrons are ultimately used to reduce NADP+ to NADPH. In the Calvin cycle, NADPH is oxidized back to NADP+ (which returns to the light reactions). The electrons released by the oxidation of NADPH are used to reduce three molecules of CO2 to sugar (G3P), which then exits the Calvin cycle.
photon
a discrete particle of light that has a fixed quantity of energy -the amount of energy is inversely related to the length of the wave -the shorter the wave the more intense the energy of each photon of that light. - the longer the wave the less intense the energy of each photon of that light
heterotrophs
'consumers' -unable to make their own food -decomposers are a type of heterotrophs that get their nutrients from dead leaves or carcauss
autotrophs
'self feeders' sustain themselves without eating anything grieved from other living beings -'producers' -self sustain and produce their own organic molecules from CO2 and other inorganic raw materials obtains from the environment -most plants are autotrophs - more specifically photoautotrophs
what is the main point of chemiosmosis in chloroplasts and mitochondria?
*create a gradient to generate ATP*!!!!! to generate ATP by the same mechanism of using an electron transport chain to pump protons (H+) across a membrane as electrons pass through a series of carriers that progress more electronegative. -through this electron transport chains transform a redox energy to a proton motive force, potential energy stored in the form of an H+ gradient across a membrane. -the ATP synthase complex in the same membrane couples the diffusion of hydrogen ions down their gradient to the phosphorylation of ADP, form ATP *creates gradient to form a proton pump to generate energy in the forming of ATP*
stage two of photosynthesis : the calvin cycle ( synthesis)
-melvin calvin -starts with the uptake of CO2 and this initial incorporation of carbon into organic compounds is known as carbon fixation -the cycles ultimate goal is to reduce the carbon molecule to a carbohydrate by the addition of electrons -the reducing power is provided by NADPH which is harvest from the electrons in the light reactions -this process also requires ATP also generated from the light reactions -the calvin cycle is sometimes referred to as the 'dark reactions' as it does not involved light directly
chloroplasts and mitochondria - chemiosmosis relationships
-the mitochondria pumps protons from the mitochondria matrix out to the inter membrane space which serves as reservoir of hydrogen ions -the thylakoid membrane of the chloroplast pumps protons from the storma (outside fluid) into the thylakoid space ( interior of the thylakoid) -the mitochondrial matrix ( inner) can be analogous to the storma (outer) of the chloroplasts during this process. they are reverse processes ( in to out) about the gradient they create
the input and outputs of the calvin cycle phase of photosynthesis ( dark reactions)
-while g3p molecules are made the actual molecule of glucose is not synthesized in this step The g3p can be used to form molecules of glucose or have other functions including going over to mitochondria to be broken down again for cellular respiration -In the Calvin cycle, the energy outputs from the light reactions (ATP and NADPH) are used to power the conversion of CO2 into the sugar G3P. As ATP and NADPH are used, they produce ADP and NADP+, respectively, which are returned to the light reactions so that more ATP and NADPH can be formed.
c4 pathways from mesophyll to bundle sheath - back
1. CO2 is present and combines with enzyme only present in a mesophyll cell called PEP carboxylase. this enzyme uses the CO2 to create a four carbon molecule called oxaloacetate. -PEP can fix carbon effciently when rubisco cannot, meaning when it is hot and dry and stomata are partially closed and CO2 concentrations are lower and O2 concentrations 2.-somehow the oxaloacetate transforms into Malate ( 4c) which is transferred to the bundle sheath cells through the plasmodesmata 3. inside the bundle sheath the malate (4c) releases a carbon which passes into a calvin cycle( within the bundle sheath. the remaining 3c molecule ( pyruvate) is transferred back through to the mesophyll. once it reaches the mesophyll ATP is spent to convert the pyruvate to PEP carboxylase allowing the cycle to continue -ATP is spent in this process so that the plant can avoid photorespiration and instead enhance sugar production -advantagous to hot regions and with intense sunlight where stomata close partially during the day
linear electron flow 4-6
4. each photo excited electrons are passed from the primary electron acceptor of PS II to PS I via the electron transport chain. -this electron transport chain is made of an electron carrier pq (plastoniquone) a cytochrome complex and a protein called pc (plastocyanin) 5.the exergonic 'fall' of electrons to a lower energy level as they pass through the cytochrome complex provides energy for the synthesis of ATP. . also as they pass through the cytochrome complex h+ ions are pumped INTO the thylakoid space, contributing to the proton gradient that is also used in chemiosmosis. *ATP made, proton gradient formed* 6. meanwhile the light energy is harvested on photosystem I's light harvesting complexes that are doing the same process to excite electrons enough to excite the chlorophyll A in the p700 to an excited state. Here again the excited p700 at its excited state passes an electron to its primary electron acceptor ( leaving a hole). this hole is then to be filled by the electron that was passed from photosystem a and through the electron transport chain. *photosystem I excites and passes and electron to have its missing electron replaced by the passed down electron from photosystem II, and which photosystem II's electron was replaced by splitting of water atom*
What is the equation that best summarizes photosynthesis?
6 CO2 + 6 H2O → C6H12O6 + 6 O2 it is essentially the reverse of the cellular respiration equation
linear electron flow 7-8
7.the excited electron from PSI primary electron acceptor is passed down an electron transport chain of its own through carrier protein Fd ( ferredoxing) but this one does not create a proton gradient --> meaning it does not generate ATP 8.from the carrier protein Fd the electron is passed and catalyzed by NADP+ reductase. However two electrons are required for NADP+ to be reduced to NADPH. After two electrons are received have a reduced NADPH. This NADPH is readily available to be entered into the calvin cycle.
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis? Temperature gradient Osmotic gradient Electrons Proton gradient
A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.
photosystem II produces ________ form of energy while photosystem I produces _________ form of energy
ATP , NADPH
What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?
CO2 is unusable until plants have "fixed" this carbon into sugar.
Calvin cycle step 1 ; Carbon fixation
CO2 molecules enter the cycle ( one at a time, or one per cycle) and is attached to a 5 carbon sugar called RuBp (ribulose diphosphate). This attachment is made by a enzyme called Rubisco -rubisco is the most abundant protein in chloroplasts and thought to be most abundant on earth - the single carbon combined with the 5 carbon sugar forms a short lived 6 carbon molecule (unstable ) which breaks into two three carbon molecules, 3-phosphoglycerate (* one carbon dioxide input, two three carbon molecules to pass to step two*)
photosystem
a complex on the membrane of the thylakoids where chlorophyll molecules are organized along with other small organic molecules and proteins in to complexes , these are photosystems
Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis? The light-independent reactions release energy, and the light-dependent reactions require energy. The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions. The light-dependent reactions pass electrons through an electron transport chain to the light-independent reactions. The light-dependent reactions produce carbon dioxide, which is then used by the light-independent reactions.
Light energy drives the formation of ATP and NADPH during the light-dependent reactions; these energy molecules are then used during the light-independent reactions to form sugars. light reactions - calvin cycle coupled reactions
light energy initially converted to chemical energy the form of two compounds which are....
NADPH and ATP
After 3-PGA is phosphorylated, it is reduced by _____.
NADPH supplies the electrons that reduce the phosphorylated 3-PGA.
Carbon fixation involves the addition of carbon dioxide to _____.
RuBp in c3 plants would be different in c4 plants
what is the main input to begin carbon fixation in most plants and in which cycle does it occur? What types of plants use this method?
RuBp and rubisco (enzyme) , in the calvin cycle c3 plants -plants where the first organic product of carbon fixation is a three carbon compound, 3 phosphoglycerate. although Rubp is actually a 5 carbon the fixation with one carbon and immediate split causes two 3c ( c3) starts
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?
The regeneration of RuBP ensures that the Calvin cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic molecule that is used to produce sugar.
photosystem parts a. reaction center complex b. light harvesting complex
a. the reaction center complex part of a photosystem surrounded by several light harvesting complexes. -this complex is an organized association of proteins holding a special pair of chlorophyll A molecules b. the light harvesting complex - outer parts of the photosystem that have various pigment molecules ( could contain a, b, or multiple carotenoids) bound to proteins. They are able to harvest light all over the outside of this because of the various pigments all over it way more efficiently than any single pigment could do. the light absorbed by the light harvesting complexes surrounding the reaction center absorb energy through its pigments and pass them down to where they are accepted by a social pair of chlorophyll a molecules ( photosystem II) -these special pair of chlorophyll a molecules are special because of their environment ( inside the reaction center) but also because they are able to use energy from light to boost one of their electrons to a higher level but also transfer it to a different molecule - the primary electron acceptor
c4 plants - bundle sheath cells -
arranged tightly packed sheaths around veins of the leaf. these are on the interior or surrounded by the mesophyll cells of a leaf. -the calvin cycle is confined to the chloroplasts of the bundle sheath cells
organic compounds are acquired in two different methods called ___________ nutrition and ________________ nutrition (two types of feeders)
autotroph; heterotroph
a global increase in CO2 would benefit c3 or c4 plants more?
c3, c4 plants already have the ability to operate with its current levels of c02 and can conserve it. -it would benefit c3 plants more because the binding to o2 rather than co2 is what cause photorespiration in c3 plants. so the increase of co2 would benefit c3 plants from causing photorespiration as much whereas c4 plants would be unaffected
what are the three types of pigments that are absorbed in chloroplasts?
chlorophyll a chlorophyll b carotenoids - do a special function called photprotection - they absorb and dissipate excessive light energy that would other wise damage chlorophyll or interact with oxygen, forming active oxiate molecules that are dangerous to the cell
all the green parts of plants have _________
chloroplasts
CAM plants
open their stomata at night and close them during the day this process is called crassulacen acid metabolism or CAM. -named after the plant family crassulacean, the succulents in which the process was first discovered. -the mesophyll cells of cam plants store organic acids they make during the night in their vacuoles until the morning, when the stomata close -udring the day when light reactions can take place the CO2 is released from the organic acids made the night before to become incorporated into sugar in the chloroplasts. -the process is very similar to c4 plants except it all takes place within the same cell as opposed to fixing co2 in one cell and transferring it to another for the calvin cycle. -acts more as a switch -*open and close stomata during the night/ day and save any products they have made during the night for the appropriate time, takes place in same cell*
Photosynthesis is a redox reaction. This means that H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.
oxidized , reduces during the light reactions of photosynthesis, water is oxidized, and during the Calvin cycle, carbon is reduced.
photosystem II Photosystem I
photosystem II ( discovered second , but reacts first in the light system process) - aka - P680 as this is the wavelength it absorbs best photosystem I ( discovered first, reacts second in the light process) - aka - P700 as this is the wavelength it absorbs best both possess nearly identical chlorophyll A molecules inside their reaction center complex and work together as the main products of the light reactions to use light energy to make ATP and NADPH
When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.
splitting water The electrons removed from water are transferred to P680 (this is in photosystem II)
the light reaction
steps to convert solar energy to chemical energy -takes place in the thylakoid membrane -water is split providing a source of electons and protons and gives off O2 as a by product -the electron acceptor in this case is NADP+ ( similar to NAD+) and functions as an electron carrier -when NADP+ is in a reduced stage it is known as NADPH by adding a pair of electrons along with the H+ - the light reaction also generates ATP through photophosphorylation
calvin cycle takes place in the ____________ Is the calvin process a catabolic or anabolic process? ____________ is the input of the calvin cycle and ________________ is the output.
stroma anabolic , it involves the building of carbohydrates from smaller molecules and consuming energy. CO2, sugar
pigments
substances that absorb light of different wavelengths, the wavelengths that are absorbed disappear. - colors that are displayed are not absorbed rather reflected -green is the color of leaves because it is the least effective color in photosynthesis, this is proved by the action spectrum
c4 plants
substitute the calvin cycle with another method of carbon fixation and starts with a four carbon molecule -sugar cane and corn are common examples of this style of plant -c4 plants possess two distinct types of photosynthetic cells ; bundle sheath cells and mesophyll cells
there are two stages of photosynthesis . What are they?
the light reactions (photo) - in which solar energy is captures and transformed into chemical energy -Generates the energy - the calvin cycle (synthesis)- uses that chemical energy to make the organic molecules of food. -uses the energy generated to produce organic molecules ( sugars ) others etc
chlorophyll a chlorophyll b
the main light capturing pigments that participates directly in the light reactions the accessory pigment
photosynthesis
the process of photosynthetic organisms capturing light energy from the sun and converting it to chemical energy that is stored in sugar and other organic molecules - this process nourishes almost the entire living world directly or indirectly
photorespiration
the results of a plant closing off their stomata. -on hot dry days plants can close their stomata, a process conserving water. -this also reduces the input of co3, concentration begin to decrease in the air spaces within the leave and the concentration of o2 released from the light reactions begins to increase. this is the wasteful process called photorespiration c3 plants an use this but is it is not as effective as normal photosynthesis process
linear electron flow 1-3
the specific flow and process electrons pass through he light reactions ( photosystem II and I) 1. photons of light hit the outer pigments of the light harvesting complexes and continue to hit and excite the electrons enough till they are able to bound enough and generate enough energy to to reach the P680 pair of chlorophyll a molecules enough to excite their electrons to a higher state of energy 2. the electron is transferred from the excited 680 ( reduced) to the primary electron acceptor leaving the p680 in an oxidized form of p680+ 3.Water molecules are split (two parts ( H2 and O ) via an enzyme to replace the passed on electrons of p680+ pair as this must be replaced ( one by one to each one of the 680 pair) the O is released into the thylakoid space where it joins up with other oxygen molecules to form O2 -(there is by product of O2 produced) from the splitting of water and sent to the thylakoid space *water split*
mesophyll
the tissue in the interior of the leaf where chloroplasts are mainly found. this would be fore c3 plants, c4 plants are the ones that also have ' bundle sheath' in which those are further inside the mesophyll cells -oxygen exists here by passing through the stomata
what is the first step of the light reactions?
the transfer of an electron from the reaction center chlorophyll a pair to the primary electron acceptors the 3rd step is replenishing those electrons by the splitting of water to have more electrons that can potentially be excited and accepted by the primary electron acceptor.