Blood and Plasma Basics

Question-and-answer flashcards reviewing the composition of blood, plasma proteins, red blood cell structure and function, hemoglobin, and erythropoiesis.

What is hematocrit?

The percentage of red blood cells (RBCs) in whole blood, averaging about 45 % in most people.

Roughly what fraction of whole blood is made up of red blood cells (hematocrit)?

Approximately 45 % (variable by individual and sex).

Which blood component forms the buffy coat, and what proportion of blood does it represent?

The buffy coat is composed of leukocytes (white blood cells) and platelets and makes up < 1 % of total blood volume.

Approximately what percentage of blood is plasma?

About 55 %.

What percentage of blood plasma is water?

Roughly 92 %.

Plasma proteins constitute about what percentage of plasma?

Approximately 7 % of plasma.

Name the most abundant plasma protein and state its primary role.

Albumin; it functions mainly as a transport protein for hydrophobic molecules and helps maintain colloid osmotic pressure.

By what name are antibodies in the plasma known?

Immunoglobulins.

Which two plasma proteins are precursors involved in clot formation and clot breakdown?

Fibrinogen (clot formation) and plasminogen (clot breakdown).

What overall effect do plasma proteins have on the osmotic balance of blood?

They generate and maintain colloid osmotic pressure.

Describe the typical shape of a red blood cell.

A biconcave disk, often compared to a donut without a complete hole.

Why are red blood cells often called “bags of hemoglobin”?

Because they lack a nucleus and mitochondria and are packed almost entirely with hemoglobin molecules.

Approximately how many hemoglobin molecules are found in a single red blood cell?

About 250 million.

How many oxygen molecules can one hemoglobin molecule bind?

Four oxygen molecules.

What hormone stimulates erythropoiesis, and which organ secretes it?

Erythropoietin (EPO), secreted by the kidneys.

What physiological condition triggers the release of erythropoietin?

Tissue hypoxia—low oxygen levels in body tissues.

Which metabolic pathway do red blood cells rely on to produce ATP, and why?

Anaerobic glycolysis, because RBCs lack mitochondria and must avoid consuming the oxygen they transport.

In which direction is oxygen transported by red blood cells?

From the lungs to the heart and then to peripheral tissues.

In which direction is carbon dioxide transported in the bloodstream?

From peripheral tissues to the heart and then to the lungs for exhalation.

How many iron atoms are present in a single hemoglobin molecule?

Four iron atoms (one in each heme group).

What is another name for red blood cells?

Erythrocytes.

What is the alternative term for white blood cells?

Leukocytes.