10.1 Photosynthesis converts light energy to the chemical energy of food …
ChloroplastsAn organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
Thylakoids A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
PhotosynthesisThe conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes.
HeterotrophsAn organism that obtains organic food molecules by eating other organisms or substances derived from them.
MesophyllLeaf cells specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis.
StromaThe fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
ThylakoidsA flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular “machinery” used to convert light energy to chemical energy.
ChlorophyllA green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Chlorophyll a participates directly in the light reactions, which convert solar energy to chemical energy.
What are the two stages of photosynthesis…
Light ReactionsThe first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.
Calvin cycleThe second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate.
NADPNicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions.
PhotophosphorylationThe process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis.
Carbon FixationThe initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote).
10.2 The light reactions convert solar energy to thee chemical energy of ATP and NADPH…
WavelengthThe distance between crests of waves, such as those of the electromagnetic spectrum.
Electromagnetic SpectrumThe entire spectrum of electromagnetic radiation, ranging in wavelength from less than a nanometer to more than a kilometer.
Visible lightThat portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm.
PhotonsA quantum, or discrete quantity, of light energy that behaves as if it were a particle.
Chlorophyll aA photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy.
Chlorophyll bAn accessory photosynthetic pigment that transfers energy to chlorophyll a.
CarotenoidsAn accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.
Describe a chlorophyll molecule …
PhotosystemA light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
Reaction-center complexA complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
Light harvesting complexA complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem.
Primary electron acceptorIn the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them.
Photo system IIOne of two light-capturing units in a chloroplasts thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P680 chlorophyll a at its reaction center.
Photosystem IA light-capturing unit in a chloroplasts thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll a at its reaction center.
Cyclic electron flowA route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or O2.
10.3 The Calvin Cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar …
Glyceraldehyde 3-phosphate (G3P)A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis.
What are the three phases of The Calvin cycle?Carbon Fixation
Energy Consumption and Redox
Release of G3P; Regeneration of RuBP
10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates…
C3 plantsA plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
PhotorespirationA metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco.
C4 PlantsA plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
Bundle-sheath cellsIn C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
PEP carboxylaseAn enzyme that adds CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate in mesophyll cells of C4 plants. It acts prior to photosynthesis.
Crassulacean acid metabolism (CAM)An adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. In this process, a plant takes up CO2 and incorporates it into a variety of organic acids at night; during the day, CO2 is released from organic acids for use in the Calvin cycle.
CAM plantsA plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. In this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.
Word Roots: auto-self;
(autotroph: an organism that obtains organic food molecules without eating other organisms)
Word Roots: chloro-green;
Word Roots: electro-= electricity;
Word Roots: hetero-= other (heterotroph: an organism that obtains organic food molecules by eating other organisms or their by-products)
Word Roots: meso-= middle (mesophyll: the green tissue in the middle, inside of a leaf)
Word Roots: photo-= light (photosystem: cluster of pigment molecules)
Word Roots: -troph= food (autotroph: an organism that obtains organic food molecules without eating other organisms)
Word Roots: -phyll= leaf (chlorophyll: photosynthetic pigment in chloroplasts)
Word Roots: magnet-= magnetic (electromagnetic spectrum: the entire spectrum of radiation)
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
NADPH > chlorophyll > Calvin cycle
H2O > NADPH > Calvin cycle
NADPH > O2 > CO2
NADPH > electron transport chain > O2
H2O > photosystem I > photosystem IIH2O > NADPH > Calvin cycle
Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.
Only heterotrophs require oxygen.
Cellular respiration is unique to heterotrophs.
Only heterotrophs have mitochondria.
Only heterotrophs require chemical compounds from the environment.Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.
Which of the following does not occur during the Calvin cycle?
release of oxygen
regeneration of the CO2 acceptor
oxidation of NADPH
consumption of ATP
carbon fixationrelease of oxygen
Which process is most directly driven by light energy?
creation of a pH gradient by pumping protons across the thylakoid membrane
removal of electrons from chlorophyll molecules
reduction of NADP+ molecules
carbon fixation in the stromaremoval of electrons from chlorophyll molecules
The light reactions of photosynthesis supply the Calvin cycle withATP and NADPH.
How is photosynthesis similar in C4 plants and CAM plants?In both cases, rubisco is not used to fix carbon initially.
In mechanism, photophosphorylation is most similar tooxidative phosphorylation in cellular respiration.
Which of the following equations represents photosynthesis?
6CO2 + 6O2 > C6H12O6 + 6H2O
6H2O + 6O2 > C6H12O6 + 6CO2
C6H12O6 + 6O2 > 6CO2 + 6H2O
C6H12O6 + 6CO2 > 6O2 + 6H2O
6CO2 + 6H2O > C6H12O6 + 6O2
6CO2 + 6H2O > C6H12O6 + 6O2Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.
In which of the following organelles does photosynthesis take place?
ChloroplastChloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen.
What connects the two photosystems in the light reactions?
An electron transport chain
A chain of glucose molecules
The Calvin cycle
An electron transport chain
What two molecules are produced by the light reactions and used to power the Calvin cycle?
CO2 and O2
C6H12O6 and O2
C6H12O6 and RuBP
ATP and NADPH
G3P and H2O
ATP and NADPHATP and NADPH are both products of the light reactions and are used to power the Calvin cycle.
What provides electrons for the light reactions?
The Calvin cycle
Electrons are stripped from water in the light reactions of photosynthesis. Light provides the energy to excite electrons.
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
Carbon dioxide (CO2)
G3P (C3H6O3)Carbon dioxide (CO2)
Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. Carbon dioxide initially combines with RuBP, and RuBP is regenerated to continue the Calvin cycle.
What transports electrons from the light reactions to the Calvin cycle?
An electron transport chain
NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle. An electron transport chain conveys electrons from one photosystem to the other within the light reactions.
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
inner membrane; outer membrane
mitochondria; chloroplaststhylakoids; stroma
Within the chloroplast, the light reactions take place in the flattened sacs called thylakoids and the Calvin cycle takes place in the thick fluid called the stroma.
Where does the Calvin Cycle take place?The Calvin cycle is a complex series of chemical reactions carried out in the stroma.
Describe Carbon Fixation in the Calvin CycleThree molecules of carbon dioxide are added to three molecules of a five-carbon sugar abbreviated RuBP. These molecules are then rearranged to form six molecules called 3-PGA, which have three carbons each.