Video Transcript
The flow chart outlines the basic
process of how a blood clot forms at the site of a wound. What word would correctly replace
the gap in statement two? (A) Collagen, (B) fibrinogen, (C)
hemoglobin, or (D) thromboplastin.
When a blood vessel is damaged,
platelets are attracted to the injury site. When they adhere to this site of
damage, it causes them to activate. This attracts more platelets to the
site of the injury, which together form a temporary platelet plug. When this plug forms, a series of
biochemical reactions to form a clot is triggered. This is what the flowchart
depicts.
The first in this sequence of
reactions is that the damaged cells release thromboplastin, which is a tissue factor
that, with the help of calcium ions, converts the blood component protein
prothrombin into the enzyme thrombin. Thrombin is an enzyme that
catalyzes the conversion of the blood component fibrinogen into fibrin threads,
which form a fibrous net over the injured area.
So, in the sequence of the
flowchart, first a blood vessel is damaged. Then damaged blood vessels release
the tissue factor thromboplastin. After that, if calcium ions are
present, thromboplastin initiates the conversion of prothrombin to thrombin. And then thrombin, an active
enzyme, catalyzes the conversion of fibrinogen into fibrin so that finally fibrin
forms a net to trap red blood cells. And the blood cells and fibrin
aggregate to form a clot.
So the word that correctly replaces
the gap in statement two is (D). Damaged blood vessels release the
tissue factor thromboplastin.
