Each state of the United States selects two senators to represent their states in the United States Senate. In 1913, the 17th Amendment[?] to the United States Constitution provided for the direct popular election of senators; prior to this, senators were selected by state legislatures.
... acceptor to ferredoxin[?], then to plastoquinone[?] (a complex of two cytochromes similar to those found in mitochondria), and then plastocyanin[?] before returning to ...