Question

Assume for the purpose of this questions that normal C3 photosynthesis is occurring. This is PS 1 (fuzzy label at bottom). a. Does light directly excite the electrons of the reaction center chlorophyll? (type Y or N on line 1) b. From where does this reaction center chlorophyll replenish electrons lost to D? (on lines 2). No sentencesl just state! C. What product is made by enzyme E? (line 3) d. In what exact location would you find the product made by enzyme E? (line 4)

Answer 1

A) No, the light does not directly excite the reaction center chlorophyll. The photosystem is made up of a complex of different chlorophyll molecules (these are associated with antenna proteins and are called as Light-Harvesting complex LHC) and a reaction center chlorophyll. The light-harvesting complex absorbs the incident sunlight that is rapidly transferred to reaction center chlorophyll which eventually excites the reaction center.

B) There are two ways that the reaction center of PS1 replenishes the electrons: (I) during non-cyclic photophosphorylation the electrons come from the PS2 (II) during cyclic photophosphorylation the released electron from PS1 return to PS1 via cytochrome complex.

C) E here is NADP+ reductase that reduces the NADP+ into NADPH. This is formed only during non-cyclic photophosphorylation.

D) The enzyme E forms the NADH at the stroma side of the thylakoid membrane.