Download INSERT 7-129a

Answers to Thinking Critically Questions
Mader: Inquiry into Life, Twelfth Edition
Chapter 7
1. Bacteria do not have mitochondria, and yet they contain an electron transport chain.
Where is this located?
Explanation/Answer: The electron transport chain must be located in a membrane in
order to set up the H+ gradient. Bacteria only have a plasma membrane so that is the
location of the electron transport chain. H+ is transported into the space between the cell
membrane and the cell wall.
2. Rotenone is a broad-spectrum insecticide that inhibits the electron transport chain.
Why might it be toxic to humans?
Explanation/Answer: The electron transport chain is not specific to insects. Humans
contain the same or similar electron carriers. A poison that affects the electron transport
chain will also affect humans.
3. What would happen to the electron transport chain if the passage of electrons was
uncoupled from the transport of H+ into the intermembrane space? Would O2 still be
required?
Explanation/Answer: If the transport of H+ did not occur, no ATP synthesis would
occur. However, the electrons would still be donated to oxygen to form water at the end
of the chain.
4. If the breakdown of one 18-carbon fatty acid chain produces 9 acetyl CoA molecules,
how many ATP are produced from this single fatty acid chain if all the molecules
complete the citric acid cycle and electron transport chain?
Explanation/Answer: The 9 acetyl Co-A molecules go through the citric acid cycle and
would each produce 1 ATP, 3 NADH + H+ and 1 FADH2 for a total of 9 ATP, 27 NADH
+ H+ and 9 FADH2. Those NADH + H+ and FADH2 would enter the electron transport
chain and produce 27 times 3 or 81 ATP for the NADH + H+ and 9 times 2 or 18 ATP for
the FADH2. The grand total would be 9 + 81 + 18 = 108 ATP.
5. Organisms that ferment have a greatly increased rate of glycolysis compared to those
that do not ferment. Why?
Explanation/Answer: Since fermentation only produces a net gain of 2 ATP molecules,
organisms that rely on fermentation must increase the rate of glycolysis in order to get
enough ATP for their uses. Pasteur was this first one to notice this phenomenon, and it is
called the Pasteur Effect.