Chapter 3: Photosynthesis Flashcards
Chlorophyll
The light-absorbing green-coloured pigment that begins the process of photosynthesis.
Porphyrin
The light-absorbing portion of the chlorophyll molecule, containing a magnesium atom surrounded by a hydrocarbon ring.
Cyanobacteria
The largest group of photosynthesizing prokaryotes.
Epidermis Layer
The transparent colourless layer of cells below the cuticle of a leaf, stem or root.
Mesophyll Layers
The photosynthetic cells that form the bulk of a plant leaf.
Guard Cells
Photosynthetic epidermal cells of a leaf or stem that form and regulate the size of an opening called a stoma.
Stomata
Openings on the surface of a leaf that allow for the exchange of gases between air spaces in the leaf interior and the atmosphere.
Transpiration
The loss of water vapour from plant tissues, primarily through stomata.
Vascular Bundles
A system of tubes and cells that transport water and minerals from the roots to the leaf cells and carry carbohydrates from the leaves to other parts of a plant, including the roots.
Stroma
The protein-rich semiliquid material in the interior of a chloroplast.
Thylakoids
A system of interconnected flattened membrane sacs forming a separate compartment within the stroma of a chloroplast.
Grana (singular: granum)
A stack of thylakoids
Lamellae (singular: lamella)
Unstacked thylakoids between grana
Thylakoid Membrane
The photosynthetic membrane within a chloroplast that contains light- gathering pigment molecules and electron transport chains.
Thylakoid Lumen
The fluid-filled space inside a thylakoid.
Light Reactions
The first set of reactions of photosynthesis in which light energy excites electrons in chlorophyll molecules, powers chemiosmotic ATP synthase, and results in the reduction of NADP+ to NADPH.
Carbon Fixation
The process of incorporating CO2 into carbohydrate molecules.
Calvin Cycle
A cyclic set of reactions occurring in the stroma of chloroplasts that fixes the carbon of CO2 into carbohydrate molecules and recycles enzymes.
Electromagnetic (EM) Radiation
A form of energy that travels at 3 X 10^8 m/s in wave packets called photons that include visible light.
Photons
Packets of EM radiation (also known as quanta)
Spectroscope
An instrument that separates different wavelengths into an electromagnetic spectrum.
Electromagnetic Spectrum
Photons separated according to wavelength.
Photosystems
Clusters of photosynthetic pigments embedded in the thylakoid membranes of chloroplasts that absorb light energy.
Action Spectrum
A graph illustrating the effectiveness with which different wavelengths of light promote photosynthesis.
Absorption Spectrum
A graph illustrating the wavelengths of light aborbed by a pigment.
β-carotene
A carotenoid pigment found in photosystems that also forms vitamin A in animals.
Xanthophylls
Pigments in chloroplast membranes that give rise to the yellow colour in autumn leaves.
Anthocyanins
Pigments in vacuoles that give rise to the red colour in autumn leaves.
Photosynthestically Active Radiation (PAR)
Wavelengths of light between 400 nm and 700 nm that support photosynthesis.
Ground State
The lowest possible potential energy level of an atom’s electron.
Fluorescene
The release of energy as light as an atom’s electron returns to its ground state.
Excitation
The absorption of energy by an atom’s electron.
Primary Electron Acceptor
A compound embedded in the thylakoid membrane that is reduced by an excited chlorophyll electron.
Antenna Complex
A web of chlorophyll molecules embedded in the thylakoid membrane that transfers energy to the reaction centre.
Reaction Centre
A transmembrane protein complex containing chloropyll a whose electrons absorb light energy and begin the process of photosynthesis.
Photosystem I
A photosystem embedded in the thylakoid membrane containing chlorophyll P700.
Photosystem II
A photosystem embedded in the thylakoid membrane containing chlorophyll P680.
Noncyclic Electron Flow
The process in which photon-energized electrons flow from water to NADP+ through electron transport chains in thylakoid membranes, producing NADPH by reduction and ATP by chemiosmosis.
Z Protein
A protein associated with photosystem II that splits water into hydrogen ions, oxygen atoms and electrons.
Phototphosphorylation
The light-dependent formation of ATP by chemiosmosis in photosynthesis.
Cyclic Electron Flow
Flow of photon-energized electrons from photosystem I, through an electron transport chain that produces ATP by chemiosmosis but no NADPH
C3 Photosynthesis
Photosyntesis in which a three-carbon intermediate is first formed when CO2 is incorporated into organic acid molecules.
Ribulose Bisposphate Carboxylase/oxygenase (rubisco)
an enzyme in the stroma of chloroplasts that catalyzes the first reaction of the Calvin Cycle; also catalyzes the oxidation of RuBP to phospho-glycolate.
Photorespiration
Oxidation of RuBP by rubisco and oxygen in light to form glycolate which subsequently releases carbon dioxide.
C4 Photosynthesis
A photosynthetic pathway of carbon fixation that reduces the amount of photorespiration that takes place by continually pumping CO2 molecules (via malate) from mesophyll cells into bundle-sheath cells, where rubisco brings them into the C3 Calvin Cycle.
Plasmodesmata
Membrane-lined channels between plant cells that allow for the movement of some substances from cell to cell.
Crassulacean Acid Metabolism (CAM)
A photosynthetic mechanism in which stomata open at night so that plants can take in Co2 and incorporate it into organic acids, and close during the day to allow the organic acids to release CO2 molecules that enter the C3 Calvin Cycle to be fixed into carbohydrates.
Light-Compensation Point
The point on a light-response curve at which the rate of photosynthetic CO2 uptake exactly equals the rate of respiratory CO2 evolution.
Light-Saturation Point
The irradiance level at which the carbon fixation reactions reach a maximum overall rate.
Photosynthetic Efficiency
A plant is defined as the net amount of carbon dioxide uptake per unit of light energy absorbed; also called quantum yield.
The one thing that all photosynthetic organisms have is common is chlorophyll.
True
The structure that connects stacks of thylakoids is the grana.
False; Lamella
Light is a form of energy that travels in wave packets called protons.
False; photons
During photosynthesis, light energy is transferred to ADP and NADP, forming ATP and NADPH.
True
The reactions of carbon fixation depend on the light reactions to supply ATP and NADPH.
True
Light energy is principally transferred by chlorophyll b.
False; chlorophyll a
A photosystem contains chlorophyll molecules, accessory pigments, and proteins embedded in a thylakoid membrane.
True
Most plants are green because that is the colour of light they need for photosynthesis.
False; because the combination of pigments absorbs light at the blue and red end of the spectrum, and green is left to reflect back to our eyes.
Photosystem I is also called P700
True
When exposed to bright white light chlorophyll fluoresces green.
False; Red
The light- saturation point is the light intensity at which the carbon fixation reactions reach a maximum overall rate.
True
In comparing respiration and photosynthesis, respiration releases energy while photosynthesis stores energy.
True
The source of electrons in photosynthesis is light.
False; water
The inner membrane of both the mitochondrion and the chloroplast is the site of their respective electron transport chains.
False; The electron transport chain is found in the thylakoid membrane.
The location of the H+ reservoir in the chloroplast is the intermembrane space.
False; interior of thylakoid.
Which of the following most accurately describes the location of chloroplasts in the leaves of most plants?
The palisade and spongy mesophyll tissues, and the guard cells of epidermal tissue.
Grana are formed from…
Thylakoids
When photosynthetic membranes are stacked in a chloroplast they are called which of the following?
Grana
In terms of the spectrum of white light, which of the following is the most effective for photosynthesis?
Blue Light
Which of the following elements is found in a molecule of chlorophyll?
Magnesium
The fact that 14O is found in the oxygen produced by photosynthesis, but not in the carbohydrate products, when photosynthesizing organisms are water labeled with 18O leads to which of the following conclusions?
The oxygen in the carbohydrate may come from carbon dioxide.
Land plants get the CO2 they need for photosynthesis mostly from …
The atmosphere
Water is lost from plants by the process of …
Transpiration
Which one of the following is NOT a characteristic of the light reactions?
Carbon Fixation Happens
Which of the following statements concerning the Calvin cycle is true?
I. ATP molecules are needed to keep the reactions going
II. The process makes NADPH +H
III. Reduction occurs
IV. Oxygen is a product
V. Photophosphorylation occurs
VI.Carbon fixation occurs.
VII. Takes place in the thylakoids of chloroplasts.
I, III, VI
ATP molecules are needed to keep the reactions going, Reduction occurs, Carbon fixation occurs.
Which of the following events of photosynthesis is concerned immediately with light?
Excitation of chlorophyll
A kind of herbicide works by disrupting the structure of the internal membranes of a chloroplast. Which segment of photosynthesis would be the most affective?
Manufacture of ATP
Electrons released as a result of photolysis …
Reduce photosystem II chlorophyll molecules.
Ultimately, the light reactions…
form ATP and NADPH +H
Photophosphorylation involves which of the following?
Chlorophyll, a proton gradient across the thylakoids, production of ATP, photons
(all of the above)
Which of the following statements concerning photolysis is correct?
I.it can take place during the fixation of carbon
II. it involves NADP
III. it occurs in the thylakoid of the chloroplast
IV. oxygen gas is produced.
V. it involves at least one carbon-containing compound.
III and IV
it occurs in the thylakoid of the chloroplast, oxygen gas is produced
When photosynthesis occurs, the oxygen that is released comes from …
Water
In photosynthesis, the function of water is to
Supply free electrons
Photosynthesis is important to the planet because it releases
Oxygen
In green plants, respiration takes place
All of the time
In green plants, photosystems I and II are required for the synthesis of NADPH.
True
The first stable product of photosynthesis in C3 plants is glyceraldehyde 3-phosphate.
False; The first stable product of photosynthesis in C3 plants is 3-phosphoglycerate.
In normal aerobic environments and saturating levels of light, an increase in CO2 concentration from 0.03% to 0.06% will result in an increase in the rate of CO2 fixation in C3 plants.
True
Photosynthesis is a redox process; that is, H2O is reduced and CO2 is oxidized.
False; Photosynthesis is a redox process; that is, H2O is oxidized and CO2 is reduced.
The enzymes required for CO2 fixation in plants are located only in thylakoid membranes.
False; The enzymes required for CO2 fixation in plants are located in the stroma in C3 and CAM plants, and in the cytoplasm of bundle sheath and mesophyll cells in C4 plants.
RuBP can be called a carbon dioxide acceptor.
True
ATP synthesis in chloroplasts occurs in the stroma.
True
Cyclic electron flow produces ATP and NADPH.
False; Cyclic electron flow only produces ATP, and not NADPH.
C4 photosynthesis is so named because it produces a four-carbon organic acid as the first stable product of carbon fixation.
True
Chloroplasts use CO2 to produce glucose; mitochondria use glucose to produce CO2.
True
Which of the following creatures would not be an autotroph?
a. cyanobacterium
b. bee
c. cactus
d. palm tree
e. Spirogyra
Bee
Photosynthesis occurs mainly in which of the following?
Mesophyll Cells
Which of the following are raw materials for
photosynthesis?
Carbon Dioxide and Water
Which word equation summarizes photosynthesis?
water + carbon dioxide oxygen + glucose + water
When does the process of splitting water to release hydrogen ions, electrons, and oxygen occur?
during the light reactions
When does the process of incorporating the carbon of carbon dioxide into carbohydrates occur?
during the Calvin cycle and during carbon fixation
What is the term for an individual flattened membrane-bound sac in the chloroplast?
thylakoid
Which of the following best describes what occurs at light levels below the light-compensation point?
Photorespiration causes a net evolution of CO2 and Photorespiration causes a net uptake of O2.
The table below summarizes data obtained in an experiement on oxygen released by different plant species grown under different lighting conditions. Assume that the plants are of comparable size .
Plant Type of light V of O2 T Time (days)
Corn Incandescent 200 20 5
Corn Fluorescent 400 22 10
Barley Incandescent 200 22 5
Barley Fluorescent 150 22 5
A fair comparison can only be made on…
Barley leaves under both lighting conditions.
Which of the following is a reasonable interpretation (from the chart)
Oxygen production is more rapid in barley in incandecsent light than fluorescent light.
Autotroph
An organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.
Heterotrophs
Organisms that feed on other organisms to obtain chemical energy.
