electron transport lecture 2 Flashcards
What is the reductant?
electron donor
What is the acceptor?
electron acceptor
How is the redox potential of a couple measured?
measured in an electrochemical cell relative to the standard hydrogen electrode (SHE)
What are the conditions for the standard hydrogen electrode?
SHE = hydrogen gas bubbled over a platinum electrode in 1 M acid solution. The reaction 2H+ + 2e– H2 is given an Eo value of 0 volts (V) by convention
What is a strong reducing agent?
is poised to donate electrons and has a negative redox potential
what is strong oxidising agent?
is ready to accept electrons and has a positive redox potential
What does Eo’ represent?
potential of a redox couple in which reduced and oxidised species
are present at 1 M concentration, 25 ºC, pH 7.
At pH 7, hydrogen electrode Eo’ = –0.42 V.
what is a spontaneous reaction?
electrons flow
from redox couple of lower potential
to redox couple of higher potential
What is the equation which determines the energy transferred for an electron over a potential difference?
Delta G = - n F delta DEo’
How do we calculate redox potentials under non standard conditions?
Nernst equation
E’ = Eo’ + (2.303 RT / nF) log10 [e– acceptor] / [e– donor]
Where do electrons from NADH enter the electron transport system
At complex 1 then flow to coenzyme Q, complex III, and complex IV
How many protons are moved across as a result of NADH?
A total of 10 H+ are concomitantly translocated.
Where do electrons enter from FADH2?
at complex II
How many electrons are pumped coos due to FADH2?
6
What is the name of complex 1?
NADH–ubiquinone oxidoreductase
What are the 3 stages that mean electrons can move through complex 1?
1 - Oxidation of NADH in the matrix releases 2e− (in the form of a hydride ion), which are transferred to FMN in a coupled redox reaction
2 -Electrons are then transferred from one carrier to another until (3)they are donated in the last step to coenzyme Q (ubiquinone; Q) to form QH2 (ubiquinol). In the process, 4H+ from the matrix side of the membrane are translocated across the membrane by complexI, and 2e− and 2H+ are used to reduce coenzyme Q.
How are the electrons transported ?
7 Fe-S centres carrying 1e- at a time
How many electrons can complex1 get through?
Translocates 4 H+ into intermembrane space
What does the poison rotenone do to complex 1?
blocks e.t. within complex I – prevents redox reaction between two Fe-S centres
What does FMN stand for?
Flavin mononucleotide
What does reduction to FMN do , via one electron?
forms a semiquinone intermediate
What does reduction via second electron do to FMN?
leads to the fully reduced species (FMNH2)
What is another name for coenzyme Q?
ubiquinone/ubiquinol
What are the key roles of coenzyme Q?
. Mobile, lipid-soluble e- carrier - transports electrons in membrane from complex I to III
- Entry point into electron transport system for e- pairs from citric acid cycle, fatty acid oxidation, and glycerol-3-phosphate dehydrogenase
- Converts 2e- transport system in complexes I and II to 1e- system in complex III, which then passes electrons one at a time to cytochrome c
