CH 461 Lecture Notes - Lecture 11: Light-Harvesting Complex, Electron Acceptor, Photosystem Ii

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silvercicada472

10 Jul 2018

School

University of Alabama

Department

Course

CH 461

Professor

Dunkel

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Document Summary

The photosynthetic scheme begins when the pigments of the light harvesting complex absorb a photon of visible light. The absorption of light excites the pigment to a higher energy state. The pigments transfer their excitation energy to the reaction center chlorophyll molecule. Two types of reaction centers exist, generally called photosystem i (psi) and photosystem ii (psii). Thus, two types of overall reactions make up photosynthesis the light and dark reactions while two more types of reactions compose the light reaction those carried out by psi and psii. Absorption of a photon causes either type of chlorophyll to become more easily oxidized that is, to give up an electron. The electron given up by either chlorophyll molecule flows through an electron transport chain, just as the electron given up by a mitochondrial cytochrome flows through the mitochondrial electron transport chain.

Related Questions

Which of the following best describes the cyclic electron transport carried out by purple photosynthetic bacteria?

A) Absorption of a photon by P960 leads to electron transport through a cytochrome bc_1 complex, then to a pool of quinones, and finally the reaction center is reduced through its quinonesB.) Absorption of a photon by P960 leads to electron transport through a cytochrome bc_1 complex, to a pool of quinones, then to a cytochrome c_2, and finally the reaction center is reduced through its quinones. C.) Absorption of a photon by P960 leads to electron transport through the reaction center quinones to a pool of quinones, to a cytochrome bc_1 complex, and finally the reaction center is reduced through its cytochrome c_2

Which best describers the relationship between photosynthetic reaction centers and light-harvesting complexes?

A) Light-harvesting complexes are needed by photosynthetic reaction centers only during episodes of dim light B.) Light-harvesting complexes absorb most of the photons, and pass the energy randomly among other such complexes until it reaches a reaction center C.) Each photosynthetic reaction center has one light-harvesting complex that directs the energy of absorbed photons to it.

Photosynthesis (Ch 8)

List the locations of the light reactions & the Calvincycle within the chloroplast and identify location on adiagram
Use the absorption spectrum of a pigment to identifywavelengths absorbed and reflected by that pigment
Describe the events of the light reactions including:

Excitation of electrons vs donation of electrons
Pathway of excited electrons through photosystem II, firstelectron transport chain, photosystem I and 2^nd electrontransport chain
Sources of electrons in photosystems I and II
ATP production using energy from an electron transportchain

List the products of the light reactions
Explain the indirect role of light reactions vs direct role ofCalvin cycle reactions in sugar production
Describe Calvin cycle events

Carbon fixation
Regeneration of CO₂ acceptor molecule (RuBP)

Explain the function of the Calvin cycle in plant cellularmetabolism
Compare & contrast electron transport and ATP synthesisbetween cellular respiration and photosynthesis

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Photosynthesis

Light Reactions:

Photosynthesis is the process of reducing/oxidizing (circle one) _____________________ to produce ___________________. This overall reduction-oxidation reaction requires _________________ to begin the flow of __________________. Photosynthetic ____________________ absorb light energy and are located in ___________________ found embedded within the membranes of __________________. The most prevalent one include the ___________________ which reflect ________________ light and absorb the other wavelengths of light. Accessory pigments include ___________________. When light energy is absorbed in photosynthesis, electrons of pigment molecules become _________________ and move into higher potential energy _______________. When the electrons return to their previous position, _____________ is passed to the ______________________ pigment molecule. Electrons within this pigment molecule move to a high potential energy state and are âgrabbedâ by _________________________ chains. Electrons from photosystem II are passed to ______________________. Electrons from photosystem I are passed to _________________. As electrons move in the electron transport chain associated with photosystem I/II (circle one), the energy released is used to power ___________ pumps and __________ is produced via a process known as ________________________. Photosystem I/II (circle one) electrons must be replaced to continue the reaction so ____________ is split for its electrons. The products _______________ & _______________ then proceed to the ______________________ cycle.

Calvin Cycle:

The Calvin Cycle can be broken into 3 main series of reactions. In the first group, known as the __________________ step, ______________________ combines with 3 molecules of ____________________ to form 6 molecules of _____________________. This reaction is catalyzed by ___________________. ________________ can act as a competitive inhibitor of this enzyme, shutting down this step in a process known as ______________________________. In the second series of reactions known as the __________________ steps, the molecules produced in the previous step get oxidized/reduced (circle one). The source of electrons is _________from the light reactions. This step is endergonic/exergonic (circle one) and thus requires _______ from the light reactions. Six molecules of _____________________ are produced, ______ (#) of which will continue in biosynthetic pathways to produce __________________. The remaining molecules will then enter the ______________________ steps which require _____________ from the light reaction. In this step, 3 molecules of _______________ are produced so that this cyclic reaction can continue.

CH 461 Lecture Notes - Lecture 11: Light-Harvesting Complex, Electron Acceptor, Photosystem Ii

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