Biology Exam chp. 8
describe the phases of the calvin cycle
1) CARBON FIXATION: 3 CO2 molecules are added to 3 RUBP (rubisco- most abundant protein in chloroplasts). that then make 6 molecules of 3-PGA. 2) REDUCTION: then products of the light reactions are used to boost the energy of these 3-PGA carbon molecules. First, 6 ATP molecules contribute Phosphate groups so they are each attached to a P. Then, 6 molecules of NADPH are oxidized giving e- to 6 carbon compounds which REDUCE THEM and generate 6G3P molecules (the sugar). - Cycle began with 15 carbons in 3 molecules of 5-carbon sugar RUBP, now are 18 carbons in form of 3 molecules of G3P. ONE MOLECULE EXITS CYCLE TO BE USED BY PLANT CELL. but other 5 are recycled to regenerate 3 RUBP molecules. 3) REGENERATION OF THE CO2 ACCEPTOR RUBP: the carbon skeletons of 5 G3P are rearranged by last steps in calvin cycle into 3 RUBP's. to do this, cycle used 3 more ATP. -SO FAR, the calvin cycle has used the products of the light reaction to reduce 3 CO2 molecules and produce 1 molecule of G3P SUGAR.
what do light harvesting complexes consist of?
Each light-harvesting complex consists of various pigment molecules (which may include chlorophyll A, chlorophyll B, and cartenoids bound to proteins. The number and variety of pigment molecules enable a photosystem to harvest light over a larger surface area and a larger portion of the spectrum than could any single pigment molecule alone.
similarities in chemiosmosis with chloroplasts and mitochondria
1) ETC proteins in the inner membrane of the mitochondrion pump protons from the mitochondrial matrix out to the inter-MEMBRANE space, serves as a reservoir of H+ ions. Similarly, ETC proteins in thylakoid membrane of the chloroplast pump protons from the STROMA into the thylakoid space, which functions as the H+ reservoir. 2) the thylakoid space and the inter-MEMBRANE space are comparable spaces in the two organelles, while the mitochondrial matrix is same to the STROMA of the chloroplast. 3) In the mitochondrion, protons diffuse down their concentration gradient from the intermembrane space through ATP synthase to the matrix, to do ATP synthesis. 4) in chloroplasts, ATP is synthesized as the hydrogen ions diffuse from the thylakoid space back to the stroma through ATP synthase complexes. so ATP forms in STROMA that is used to drive sugar synthesis in calvin cycle
1) the excited state e- passes from the primary e- acceptor PSII to PSI via _____ which is made up of 3 things: 2) each of these reactions down the ETC create free energy that is then used to create a ___ ___ across the thylakoid membrane. and potential energy stored here makes _____ by a process called _____
1) an ETC which is made up of pQ cytochrome complex and PC 2) proton gradient, ATP, chemiosmosis
1) what are photosystems ? 2) what connects the two photosystems ?
1) clusters of chlorophyll and proteins that capture light energy. 2) ETC
explain the process in brief of what happens during cellular respiration to later compare to photosynthesis
1) energy is released from sugar when electrons associated with hydrogen are transported by carriers to oxygen, forming water as a by-product 2) The electrons lose potential energy as they "fall" down the electron transport chain toward electronegative oxygen, and the mitochondrion harnesses that energy to synthesize ATP
series of linear electron flow on how it generates ATP and NADPH steps !!
1) photon like strikes in PSII complex and boosts e- to higher energy level. continues process 2) e- transferred from excited P680 to primary e- acceptor. so resulting in P680+ (strongest oxidizing agent, so e- has to be replaced) 3) enzyme splits water molecule into 2 e-, 2 H+, and 1 O. The H+ are released into the thylakoid space then the O atom combines with the O atom that was generated by the splitting of another water molecule to make O2. 4) each excited e- goes to PS1 now and carries out redox reaction as e- flow down the ETC, releasing free energy that is used to pump H+ into the thylakoid space. 5) potential energy stored in the proton gradient is used to make ATP by Chemiosmosis. 6) light energy has been transferred by light-harvesting complex pigments to PS1 reaction center, exciting an e- of the P700 of chlorophyll A. Then e- is transferred to PS1's primary electron acceptor making it P700+ and an e- acceptor that reaches the bottom of the ETC 7) photoexcited e- are passed down series of redox rxns from primary e- acceptor of PS1 down a second ETC through protein FERREDOXIN (does not create a proton gradient so doesnt make ATP) 8) enzyme NADP+ reductase catalyzes transfer of electrons from FERREDOXIN to NADP+. two electrons required here for its reduction TO NADPH. ELECTRONS IN NADPH ARE AT A HIGHER ENERGY LEVEL THAN THEY ARE IN WATER so they are more readily available for the reactions of the Calvin cycle. This process also removes an H+ from the stroma.
1) both PSII and PS1 are the purple blocks and made up of ___ and ____ . 2) each photosystem has a ___ ___ ___ (smaller light purple rectangle)
1) proteins, and pigment molecules in green. 2) reaction center complex
how many e- are required for the full reduction of NADP+ to NADPH
2 e-
what exactly are embedded in the thylakoid membranes of a chloroplast
2 photosystems, 2 ETC, and 1 ATP synthase
how many electrons are passed to the primary electron acceptor for every molecule of O2 that is released from PSII ??
4 electrons must be released from water and passed on to the primary electron acceptor one at a time to form one molecule of O2
photosynthesis equation
6CO2 + 6H2O + light energy ------> C6H12O6 + 6O2
for the net synthesis of one G3P molecule, how much of what does the calvin cycle consume
9 molecules of ATP and 6 of NADPH.
Photorespiration
A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output AND MAKES NO SUGAR!! ; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds carbon dioxide.
in light reactions, light drives the synthesis of ____ and ____
ATP and NADPH
the light reactions in the thylakoid product what 2 products ?? that will now power the production of sugar in the ____ ____
ATP, NADPH Calvin Cycle
what does chlorophyll A do
Absorbs sunlight. light-capturing pigment that participates directly in the light reactions
what does chlorophyll B do?
Accessory pigment helps chloroplast absorb light energy
Chemiosmosis
An electron transport chain pumps protons H+ across a membrane as electrons are passed through a series of carriers that are progressively more electronegative.
the calvin cycle converts ____ into ____. this also requires chemical energy in the form of ATP that is generated by the light reactions
CO2 into a carbohydrate.
in calvin cycle ATP and NAPH (products of the light reaction) power the conversion of ___ into ____
CO2, sugar
the Calvin cycle incorporates ___ into organic molecules which are then converted to ____
CO2. Calvin CO2, sugar
the carbohydrate made from the calvin cycle isnt glucose but ____
G3P
primary electron acceptor
In the thylakoid membrane of a chloroplast, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll A molecules and accepts an electron from them.
reminder: what functions as the electron carrier in cellular respiration? and what is its cousin in photosynthesis
NAD+ NADP+
light absorbed by the chlorophyll drives transfer of electrons and H+ from water to an acceptor called
NADP+
the light reactions use solar energy to reduce ____ to ____ by adding a pair of electrons along with an H+
NADP+, NADPH
on the outside of the thylakoids, NAD+ and ATP pick up a phosphate and electrons to release ___ and ___ into the stroma for the CALVIN CYCLE
NADPH, ATP
the calvin cycle makes sugars but only by the help of ___ and ___ produced by the light reactions
NADPH, ATP
does the calvin cycle require direct light in these cycles ?
NO
do light reactions produce sugar?
NO that is saved for the calvin cycle
some of the sugars made during photosynthesis are used during cellular respiration using ___ in the plants _____ to generate ATP to power other work in the plants.
O2, mitochondria
when water is split, it provides a source of electrons and H+ that gives what as the by-product in photosynthesis
Oxygen O2
PSII = split H2O molecules that supply electrons back to PSI which then expels electrons in NAD+ to make NADPH (in light reaction before calvin)
PSII = split H2O molecules that supply electrons back to PSI which then expels electrons in NAD+ to make NADPH
P680 and P700 are in which PSI and PSII?
PSII has P680 PSI has P700
Beginning of the calvin cycle, CO2 molecules combine with ____ molecules. the resulting molecules go through a series of reactions powered by ____ and _____ from the light reactions. What are produced from this ?
RUBP ATP, NADPH sugar molecules known as G3P
Carbon Fixation (Calvin Cycle)
The initial incorporation of carbon CO2 into organic compounds.
Photophosphorylation
The process of generating ATP from ADP and phosphate by proton-motive force (chemiosmosis) created by the thylakoid membrane of the chloroplast during the light reaction.
what is one of the first steps in a light reaction?
The solar-powered transfer of an electron from the reaction-center chlorophyll A pair to the primary electron acceptor
what two types of photosystems is the thylakoid membrane populated by? which functions first in the light reactions?
They are called photosystem II (PS II) and photosystem I (PS I). PSII functions first
the calvin cycle reduced the fixated carbon to ____ by the addition of electrons. the reducing power is ____
carbohydrates, NADPH
what are the three phases of the calvin cycle
carbon fixation, reduction, regeneration of CO2 acceptor
the citric acid cycle is ___ while the calvin cycle is ____ BUILDING carbohydrates from smaller molecules and consuming energy
catabolic, (breaking down) anabolic (BUILDING UP)
what is the most abundant organic molecule in a plant
cellulose
green pigment that gives leaves its color
chlorophyll
why do leaves look green
chlorophyll absorbs violet blue and red light while REFLECTING GREEN LIGHT
what is a photosystem
composed of a reaction-center complex surrounded by several light-harvesting complexes. The reaction-center complex is an organized association of proteins holding a special pair of chlorophyll A molecules and a primary electron acceptor.
in both organelles P and E,
electron transport chains pump protons H+ across a membrane from a region of low H+ concentration to high H+ concentration. The protons then diffuse back across the membrane through ATP synthase driving the synthesis of ATP
light reactions summary: linear electron flow from txt. Video
electrons from H2O move through PSII and then down an ETC, providing energy for the synthesis of ATP. electrons continue on through PS1 and then down another electron transport chain that contains FERREDOXIN ending up in NADPH !!! WOOO
plants split H2O as a source of ____ from hydrogen atoms, releasing _____ as a by product
electrons, O2
Because the electrons INCREASE IN POTENTIAL ENERGY DURING PHOTOSYNTHESIS as they move from water to sugar, this process is _____
endergonic
the shorter of wavelength the ___ the energy of each photon of the light
greater
e- in NADPH are at a ____ energy level than in water where the e- started. so they are more readily available for calvin cycle rxns
higher
absorption of a photon boosts an electron to a ___ ___ ___ shell and the pigment molecule is in an excited state
higher- energy electron
Where are chloroplasts mainly found
in mesophyll
where does the calvin cycle take place
in the stroma
what are the sites of the Calvin cycle
in the stroma, the grey parts
where is the H+ concentration gradient located? This also contained the O2 split from water that is expelled from plants (in light reaction before calvin)
in the thylakoid compartment that is then used by the ATP synthase to make ATP
where does chlorophyll reside
in the thylakoid membranes of the chloroplast.
the first phase of photosynthesis, the light reactions, what happens
in the thylakoids, light energy is converted into chemical energy
the two processes of photosynthesis are
light reactions (photo part in photosynthesis) and the Calvin cycle (synthesis part)
how mitochondria use chemiosmosis versus chloroplast
mitochondria use chemiosmosis to transfer chemical energy from food molecules to ATP, where chloroplasts use it to transform light energy into chemical energy in ATP.
What are cartenoids?
other accessory pigments that are yellow, orange bc they absorb violet and blue-green light. these are HYDROCARBONS
chemiosmosis: an ATP synthase complex in same membrane couples the diffusion of H+ down their concentration gradient to the ______ of ADP to form ATP
phosphorylation
purple has twice as much ___ ____ than red light with a longer 780nm wavelength
photon energy
light has discrete particles called
photons
important function of cartneoids
photoprotection: These compounds absorb and dissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen to form reactive oxidative molecules that are dangerous to the cell.
chloroplasts and thylakoid membraned contain light absorbing molecules called
pigments at different wavelength
the high concentration of H+ ions in the thylakoid powers what in the light reactions ? producing what
powers ATP synthase, producing ATP
in photosynthesis the 6CO2 to C6H12O6 becomes ____ and the 6H2O to 6O2 becomes ____
reduced because gaining a H, and oxidized because LOSING a H
in comparison to cellular respiration, photosynthesis reverses _________ .....
reverses the direction of electron flow. Water is split, and its electrons are transferred along with hydrogen ions H+ from the water to carbon dioxide, reducing it to sugar.
what do the thylakoids do
segregates the stroma from the thylakoid space inside these sacs. In some places, thylakoid sacs are stacked in columns called grana
the light reactions use ___ ___ to make ___ and ____
solar energy, ATP and NADH
the light reactions use __ ___ to generate ATP that provides ___ _____ and NADPH that provides ___ ___ to the carbohydrate synthesizing reactions of the calvin cycle.
solar power chemical energy reducing power
light reaction are steps of photosynthesis that convert ____ energy to ___ energy
solar, chemical
CO2 enters leaf, and oxygen exits by way of microscopic pores called
stomata
WHERE is the calvin cycle carried out
stroma
chloroplast has envelope of two membranes surrounding dense fluid called
stroma
the chloroplast uses light energy to make sugar by coordinating the two stages of photosynthesis.
the chloroplast uses light energy to make sugar by coordinating the two stages of photosynthesis.
series sep when a pigment molecule absorbs a photon:
the energy is transferred from pigment molecule to pigment molecule within a light harvesting complex until its passed to the pair of chlorophyll A molecules in the reaction-center complex.
what happens when a chlorophyll electron is excited to a higher energy level?
the primary electron acceptor captures it; this is a REDOX reaction.
linear electron flow
the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
what is the most important product of the photosynthesis ? some are used to build ____ to make ____ and some are used to make _____
the remaining G3P sugar. some are used to build glucose (combine to starch or cellulose) // or sucrose
Chloroplasts do not need molecules from food to make ATP.
their photosystems capture light energy and use it to drive the electrons from water to the top of the transport chain.
for the net synthesis of one molecule of G3P the cycle has to take place ____ times, fixing ____ molecules of CO2
three, 3 molecules of CO2 one per turn of the cycle
in the stroma, a third membrane made up of sacs is the
thylakoid
what are the sites of the light reactions
thylakoid membranes the green part
the calvin cycle takes place outside the ____ in the _____ (the thick fluid of the chloroplast)
thylakoid, stroma
the excited state is ___ so the electron cannot stay there long. when this happens, when pigments absorb light, their excited electrons drop back down to their ground state FAST releasing their excess energy as ____ or ___
unstable, HEAT or LIGHT
what colors does chlorophyll a suggest best work for photosynthesis? and the least work (thats why its reflected)?
violet- blue and red light= best green= worst
How does the calvin cycle begin again ?
when G3P molecules are converted back to RUBP's
