Video Transcript
The diagram provided shows a basic
outline of the process of glycolysis. The circles are used to represent
the number of carbons in the compounds involved. What compound has been replaced by
the letter Z? (A) Sucrose, (B) inorganic
phosphate, (C) pyruvate, or (D) carbon dioxide.
Cellular respiration is performed
by cells to release energy from carbon-containing compounds, such as glucose, and
transfer it to molecules of ATP. The energy can then be used by the
cells to power metabolic reactions and carry out essential processes like
digestion, breathing, and movement.
Glycolysis is the first stage of
both aerobic and anaerobic respiration and occurs in the cytoplasm of the cell. Glucose, a six-carbon
monosaccharide, is the primary reactant of glycolysis.
Let’s now take a look at the
process of glycolysis in more detail.
The first thing that happens is
that the glucose molecule is phosphorylated, which means phosphate groups are
added. These phosphate groups come from
two adenosine triphosphate, ATP, molecules. Tri- meaning three, so ATP has
three phosphate groups. Each molecule of ATP donates one
phosphate group and hence becomes an adenosine diphosphate molecule, di- meaning
two. This resulting phosphorylated
glucose is also a six-carbon sugar.
In the next step, the
phosphorylated glucose molecule, also known as fructose-1,6-diphosphate splits to
form two three-carbon molecules. These molecules have several
different names. So depending on your syllabus, they
could be any one of glyceraldehyde-3-phosphate, G3P; phosphoglyceraldehyde, PGAL; or
triose phosphate, TP. So try not to get confused.
In the final step, the
glyceraldehyde-3-phosphate molecules each lose a hydrogen but at the same time bind
to another phosphate group. The resulting molecules then lose
both their phosphate groups. These four phosphate groups, two
from each molecule, are picked up by ADP, forming a total of four ATP. The final products of glycolysis
are two lots of the three-carbon molecule pyruvate, also known as pyruvic acid.
Having reviewed the key facts about
glycolysis, let’s return to our question. We now know that the correct answer
is (C). The three-carbon intermediate
molecule that is the product of glycolysis is known as pyruvic acid or pyruvate.
