Video Transcript
For each molecule of glucose that
enters glycolysis, how many turns of the Krebs cycle will there be? (A) One turn, (B) two turns, (C)
four turns, (D) six turns.
Cellular respiration is an
important process in all living organisms. It is the process in which glucose
is broken down to release energy that is then stored in molecules of ATP. There are four main steps in
cellular respiration: glycolysis; the link reaction; the Krebs cycle, sometimes
called the citric acid cycle; and oxidative phosphorylation, also known as the
electron transport chain. Each of these steps produces
products that are reactants for the next step. So the products of glycolysis are
the reactants for the link reaction. And the products of the link
reaction are the reactants for the citric acid cycle.
In glycolysis, glucose is converted
into two molecules of pyruvate. Then, in the link reaction, these
two molecules of pyruvate are each converted into a molecule of acetyl coenzyme A or
acetyl-CoA. Each acetyl-CoA can then enter the
Krebs cycle to produce ATP, NADH, and FADH2.
Let’s look back at our question
about the number of turns of the Krebs cycle for each molecule of glucose. Because there’s two pyruvates
formed after glycolysis, there will be two acetyl-CoA molecules formed, and
therefore two rounds of the Krebs cycle. So the correct answer choice is
(B), two turns.
