A&P 2- Red Blood Cells: Structure and Function
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35 Terms
What is another name for a red blood cell?
Erythrocyte.
What is the main function of red blood cells?
Transport most oxygen from the lungs to tissues.
What gas do RBCs also transport from tissues to lungs?
Some carbon dioxide.
Why are RBCs needed for oxygen transport?
Plasma cannot carry enough oxygen by itself, so RBCs carry most of it.
About what percentage of the formed elements are RBCs?
About 99.9%.
What is the approximate RBC count per microliter of blood?
About 4–6 million RBCs per microliter.
What is a hematocrit?
The percentage of blood volume made up mainly by red blood cells, measured after centrifugation.
How is a hematocrit obtained?
By centrifuging a blood sample to separate formed elements from plasma.
What is the buffy coat?
The thin layer of white blood cells and platelets after centrifugation.
What does a hematocrit of 42% mean in the example?
About 42% formed elements and 58% plasma.
What are mature RBCs like structurally?
Very small, highly specialized cells with no nucleus and few other organelles.
Why can mature RBCs not repair themselves well?
They lack a nucleus and most organelles.
What protein are RBCs densely packed with?
Hemoglobin.
What shape are RBCs?
Biconcave discs.
Why is the biconcave shape useful?
It provides a large surface-area-to-volume ratio for rapid gas exchange.
How does the biconcave shape help RBCs travel through capillaries?
It allows them to stack, bend, and flex.
What is hemoglobin?
A globular protein in RBCs that carries oxygen.
How many polypeptide subunits does hemoglobin have?
Four.
What are the four hemoglobin subunits?
Two alpha chains and two beta chains.
What does each hemoglobin subunit contain?
One heme molecule.
What is heme?
A pigment molecule containing ionized iron, Fe2+.
What does Fe2+ in heme do?
It reversibly binds an oxygen molecule.
About how many hemoglobin molecules are in one RBC?
About 280 million.
About how many oxygen molecules can one RBC carry?
More than one billion.
Why can a mature RBC no longer make new hemoglobin?
It loses its nucleus before maturity.
What happens to hemoglobin in the lungs?
It binds oxygen because oxygen concentration is high.
What is oxyhemoglobin?
Hemoglobin bound to oxygen; it is bright red.
What happens to oxygen at peripheral tissues?
It dissociates from heme iron where oxygen concentration is low.
What is deoxyhemoglobin?
Hemoglobin after oxygen has been released; it is darker red-blue.
Why is carbon monoxide dangerous?
It binds to heme iron and prevents oxygen from binding.
What is abnormal in sickle-cell anemia?
The beta chain of hemoglobin.
What happens to RBCs in sickle-cell anemia under low oxygen?
Hemoglobin molecules interact abnormally, causing the cells to become stiff and curved.
Why can sickled RBCs be dangerous?
They can back up or block blood vessels.
What do the notes say about a person carrying one sickle-cell trait?
They may show no signs and may have some protection against malaria.
What other hemoglobin disorder is mentioned in the handwritten notes?
Thalassemia.