Video Transcript
The flowchart outlines the basic
process of how a blood clot forms at the site of a wound. What word would correctly replace
the gaps in statements 4 and 5? (A) Fibrin, (B) keratin, (C)
collagen, or (D) myoglobin.
Blood clotting is the process in
which our blood coagulates and forms a thick mass, which plugs up wounds in our
blood vessels and stops excess blood loss. The process of blood clotting
involves a cascade of biochemical reactions, which are described in statements 2 to
5 in the flowchart provided by the question. We are being asked to find a word
that replaces the gaps in statements 4 and 5 in the flowchart, so let’s take a
closer look at the process of blood clotting to find the answer.
When a blood vessel is damaged, as
described in stage 1 of the flowchart, platelets are attracted and adhere, or stick,
to this damaged site. This causes these platelets to
become activated, which attracts even more platelets, eventually forming a platelet
plug, which blocks up the damaged site and prevents excess blood loss from the
wound. These activated platelets, together
with the damaged blood vessel and the surrounding tissues, produce an enzyme called
thromboplastin, which is described in stage 2 of the flowchart.
In the presence of calcium ions,
thromboplastin acts on a protein produced by the liver called prothrombin,
converting it into an active enzyme called thrombin, as stated in stage 3 of the
flowchart. Thrombin then acts on a protein
called fibrinogen, which is soluble in blood plasma. This reaction is the one that
begins to be described in statement 4 in the flowchart whereby fibrinogen is
converted into an insoluble fiber called fibrin. Fibrin then forms a net to trap red
blood cells and more activated platelets, which aggregate together to form a fully
formed clot, as described in statement 5 in the flowchart.
We now know the correct answer to
the question. The word that would correctly
replace the gaps in statements 4 and 5 is fibrin.
