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Homework #10 (130107): Chapter 10 (141107)

Total points: 20 for Attempt on all questions

ONE Concept Map: 10 pointsObjectives

The Process That Feeds the Biosphere1. Distinguish between autotrophic and heterotrophic nutrition.

-sustain themselves-produced by othersAutotrophic nutrition means being able to feed themselves. Heterotrophic nutritionmeans living on compounds produced by other organisms.

2. Distinguish between photoautotrophs and chemoautotrophs.

-use light energy

-inorganic compounds

Photoautotrophs use light energy, while chemoautotrophs use inorganic compoundsas energy.

3.

Describe the structure of a chloroplast, listing all membranes and compartments.

-stomata

-stroma

-thylakoids

-chlorophyll

Chloroplasts are made up of chlorophyll. A chloroplast has an envelope of twomembranes surrounding a dense fluid called the stroma. Suspended within thestroma is a third membrane system, made up of sacs called thylakoids, whichsegregate the stroma from the thylakoid space inside these sacs. Chlorophyll is thegreen pigment that give leaves their color.

The Pathways of Photosynthesis

4. Write a summary equation for photosynthesis.6CO2 + 6H2O C6H12O6 + 6O2.

5. Explain van Niel's hypothesis and describe how it contributed to our currentunderstanding of photosynthesis. Explain the evidence that supported his hypothesis.

-oxygen-18

-shuffling of atoms

-photosynthesis

Scientists confirmed van Neils hypothesis by using oxygen-18 as a tracer to followthe fate of oxygen atoms during photosynthesis. A significant result of the shuffling ofatoms during photosynthesis is the extraction of hydrogen from water and intsincorporation into sugar.

6. In general terms, explain the role of redox reactions in photosynthesis.

-oxidation

-photosynthetic electron transport chainThe oxidation of water is linked with the reduction of CO2 through a series of redoxreactions in which electrons are passed from one compound to another. This series

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of reactions constitutes the photosynthetic electron transport chain. The process

begins with the absorption of light by protein-pigment complexes known as

photosystems. Photosystems use absorbed light energy to drive redox reactions and

thereby set the photosynthetic electron transport chain in motion. In turn, themovement of electrons through this transport chain is used to drive the synthesis of

ATP and NADPH. And finally, ATP and NADPH are the energy sources needed tosynthesize carbohydrates using CO2

7. Describe the two main stages of photosynthesis in general terms.

-photo reactions

-synthesis reactionsPhotosynthesis involves light-dependent "photo" reactions and light-independent

"synthesis" reactions. Traps energy from sunlight into bonds of energy carriers (ATP

and NADPH) in the thylakoid. energy then transferred to and stored in chemicalbonds of carbohydrates

8. Describe the relationship between an action spectrum and an absorption spectrum.Explain why the action spectrum for photosynthesis differs from the absorption

spectrum for chlorophyll a.-chlorophyll

-absorption spectrumAction spectrum of photosynthesis follows absorption spectrum of chlorophyll. Theabsorption spectrum indicates how much of each wavelength chlorophyll will

absorb, whereas the action spectrum can tell us which off those wavelengths are

most effective in photosynthesis.

9. Explain how carotenoids protect the cell from damage by light.

-ascorbate

-beta-carotene

Ascorbate, beta-carotene, and other antioxidants are able to neutralize reactiveoxygen species. These are chemicals that detoxify reactive oxygen species

10.List the wavelengths of light that are most effective for photosynthesis.

-blue

-redLight most effective for photosynthesis absorbs in blue (400-450 nm) and red (650-700 nm) wavelengths. Chlorophyll appears green because it reflects green

wavelengths (500 to 600 nm).

11.Explain what happens when a solution of chlorophyll aabsorbs photons. Explainwhat happens when chlorophyll ain an intact chloroplast absorbs photons.

-rapidly released

-convert to heat

-reaction centerFor chlorophyll molecules that have been isolated in the laboratory, this absorbedlight energy is rapidly released, allowing the electron to return to its initial "ground"

energy state. Most of the energy is converted into heat; a small amount is reemitted

as light). By contrast, The absorbed light energy is transferred to anotherchlorophyll molecule and then on to another. Absorbed light energy is transferred

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from one chlorophyll molecule to another until it is finally transferred to the reaction

center. When the transfer takes place, the reaction center becomes oxidized and the

adjacent electron-acceptor molecule is reduced.

12.List the components of a photosystem and explain the function of each component.

-photosynthetic pigment

Chlorophyll is the major photosynthetic pigment, sunlight, accessory pigmentsallows photosynthetic cells to absorb a broader range of visible light than would be

possible with just chlorophyll alone. Antenna= Absorbed light energy is transferred

from one chlorophyll molecule to another. the reaction center is where light energyis converted into electron transport.

13.Trace the movement of electrons in noncyclic electron flow. Trace the movement ofelectrons in cyclic electron flow.

-PS II

-PS 1Non-Cyclic Electron Flow - uses PS II and PS I. Photosystem II supplies electrons tothe beginning of the electron transport chain. When photosystem II loses an electron

(that is, when it is itself oxidized), it is able to pull electrons from water. In contrast,photosystem I energizes electrons with a second input of light energy so they haveenough energy to reduce NADP+.

14.Explain the functions of cyclic and noncyclic electron flow.

-compensate

-reduce NADP+Ciclic electron flow = used to compensate for higher ATP requirements. Non-cyclicelectron flow = electron energy can be uses to reduce to NADP+ (NADH in cellular

respiration).

15.Describe the similarities and differences in chemiosmosis between oxidative

phosphorylation in mitochondria and photophosphorylation in chloroplasts.-photophosphorylationIn Photosynthesis electron flow from light through pigment molecules providesenergy for ATP synthesis = PHOTOPHOSPHORYLATION. In Cellular Respiration -

electron flow from oxidation of glucose through glycolysis / pyruvate oxidation /

citric acid cycle provides energy for ATP synthesis = OXIDATIVEPHOSPHORYLATION. Mitochondrion--pumps H+ out --transfers chemical energy

from food to ATP- matrix. Chloroplast--- pumps H+ in-- transforms light energy to

ATP --in stroma

16.State the function of each of the three phases of the Calvin cycle.

-carboxylation

-reduction

-regeneration1) Carboxylation = the addition of CO2 to the 5 carbon compound, RuBP is

catalyzed by the enzyme ribisco. Carbon fixation of CO2 to 3PG. 2) Reduction =NADPH transfer high-energy electrons; conversion to carbohydrate (G3P). 3)

Regeneration of RuBP = process, 3-C compound are reorganized and combined to

produce RuBP

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17.Describe the role of ATP and NADPH in the Calvin cycle.

-More atp is used

-3 for every 2More ATP is used than NADPH+H+ in Calvin Cycle. 3 ATP consumed for every 2

NADPH+H+ used. Extra ATP used in regenerating RuBP - extra ATP produced inCyclic Electron Flow

18.Describe what happens to rubisco when O2concentration is much higher than CO2concentration.

-oxygenaseRubisco can act as an oxygenase (catalyzes O2 fixation) = photorespiration. Rubisco

can bind O2 in place of CO2.

19.Describe the major consequences of photorespiration. Explain why it is thought to bean evolutionary relict.

-requires ATPrequires ATP. when atmosphere had less O2 and more CO2. Inability of enzyme toexclude O2 wouldnt matter. Now photorespiration is inevitable.

20.Describe two important photosynthetic adaptations that minimize photorespiration.

-CO2 added to PEP

-break downIn C4 plants, CO2 is first added to a three-carbon compound, PEP, with the aid ofan enzyme (PEP carboxylase) that has a high affinity for CO2. The resulting four-

carbon compound formed in the mesophyll cells of the leaf is transported to bundle-

sheath cells tightly packed around the veins of the leaf. The compound is broken

down to release CO2, which rubisco then fixes into the Calvin cycle. In CAM plants,they break down the compounds down to release CO2 during daylight so that the

Calvin cycle can proceed. The process of succulent plants close their stomata duringthe day to prevent water loss, but open at night to take up CO2 and incorporate itinto a variety of organic acids. The CAM pathway does not structurally separate

carbon fixation from the Calvin cycle

21.List the possible fates of photosynthetic products.

-sugar.Sugar made in the chloroplasts supplies the entire plant with chemical energy and

carbon skeletons for the synthesis of all the major organic molecules of plant cells.

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Key Words to Construct Concept Maps

absorption spectrumaction spectrumautotrophbundle-sheath cellC3plantC4plantCalvin cycleCAM plantcarbon fixationcarotenoidchlorophyllchlorophyll achlorophyll bcrassulacean acid metabolism (CAM)

cyclic electron flowelectromagnetic spectrumglyceraldehyde-3-phosphate (G3P)heterotrophlight reactionslight-harvesting complexmesophyllmesophyll cellNADP

+

noncyclic electron flowPEP carboxylasephoton

photophosphorylationphotorespirationphotosynthesisphotosystem

photosystem I (PS I)

photosystem II (PS II)primary electron acceptor

reaction center

rubisco

spectrophotometerstoma

stromathylakoid

visible lightwavelength

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