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an input of energy. Hin t 1. Comparing the energy requirements of chloroplast and mitochondrial electron transport chains
In a c hloroplas t, photos y nthetic elec tron trans port between Pq (plas toquinone) and Pc (plas toc y anin) v ia the c y toc hrome c omplex is nearly
identic al to the c entral portion of the elec tron trans port c hain in a mitoc hondrion.
Rec all that in a mitoc hondrion, onc e elec trons enter the elec tron trans port c hain from NADH, no additional input of energy is needed to power
elec tron flow to O2. Think about how this s imilarity applies to the energy requirements of the photos y nthetic elec tron trans port c hain. Hin t 2. How is light energy used in Photosystem II?
When light energy is abs orbed by a c hlorophy ll molec ule, an elec tron in the c hlorophy ll is boos ted to a higher energy lev el. This form is c alled
the ex c ited s tate of the c hlorophy ll.
How is the energy of the excited state of P680 chlorophyll used in Photosystem II?
The ex c ited s tate of P680 remov es an elec tron from the primary elec tron ac c eptor.
The ex c ited s tate of P680 donates an elec tron to the primary elec tron ac c eptor.
The ex c ited s tate of P680 remov es an elec tron from water. Hin t 3. What is the effect of artificially (without light) reducing NADP+ to NADPH?
Suppos e that a partic ular c ompound X, when added to a s olution of func tioning c hloroplas ts , c aus es the reduc tion of NADP+ to NADPH in the
dark . Howev er, when X is mix ed with NADP+ in the abs enc e of c hloroplas ts , no reduc tion of NADP+ to NADPH oc c urs . In other words ,
c ompound X c annot direc tly reduc e NADP+ to NADPH.
Which of the following m ust also occur when com pound X is added to chloroplasts in order to account for the observed reduction of
NADP+ to NADPH in the dark?
Elec tron c arriers between PS II and PS I (s uc h as plas toquinone) mus t be reduc ed.
In PS I, P700 mus t be ox idiz ed to P700+.
Water mus t be ox idiz ed and O2 mus t be...
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This document was uploaded on 02/17/2014 for the course BIOCHEMIST 2550 at Ohio State.
- Spring '14