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Example Questions
Example Question #341 : General Biology
Every heme group in hemoglobin encloses an atom of what element?
Chromium
Iron
Magnesium
Copper
Iron
Each heme group in hemoglobin encloses a single iron atom in the center of a protoporphyrin, a tetrapyrrol composed of four pyrrole rings linked together by four methyl groups, two vinyl groups, a methane bridge, and two propinoic acid side chains.
Example Question #342 : General Biology
What is the average lifespan of an erythrocyte?
6 weeks
4 months
3 months
6 months
4 months
The average lifespan of a red blood cell is 4 months, after which it is phagocytosed by macrophages the spleen, liver, or lymph nodes. White blood cells, on the other hand, live for only about 3-4 days.
Example Question #343 : General Biology
What hormone stimulates the casting of new red blood cells?
Thyroxine
Erythropoietin
Vasopressin
Luteinizing hormone
Erythropoietin
The casting of new red blood cells is stimulated by the hormone erythropoietin (EPO), released from the kidneys. Recall that all blood cells are made in the bone marrow. This hormone may increase as much as 1000 fold in times of oxidative stress.
Thyroxine is T4, the most biologically active form of thyroid hormone. Vasopressin, or anti-diuretic hormone, is part of the body's fluid-balance system. Luteinizng hormone is a hormone of the reproductive tract: in females it triggers ovulation, while in males it stimulates Leydig cells to produce testosterone.
Example Question #344 : General Biology
Where is erythropoietin produced?
Zona fasciculata cells of the adrenal glands
Lactotroph cells in the pituitary gland
Supraoptic and paraventricular cells of the hypothalamus
Peritubular interstitial cells of the kidney
Peritubular interstitial cells of the kidney
Erythropoietin is produced by the peritubular interstitial cells of the kidney. These cells are very sensitive to tissue oxygen pressure. When oxygen demand increases, erythropoietin is released, stimulating the casting (hematopoiesis) of new red blood cells in bone marrow.
Supraoptic and paraventricular cells of the hypothalamus are the site of vasopressin (antidiuretic hormone) production. Lactotroph cells in the pituitary gland are responsible for the production of prolactin. Zona fasciculata cells of the adrenal glands produce cortisol.
Example Question #1 : Blood And Plasma
Neutrophils make up what percent of white blood cells in the blood?
20-35%
55-70%
2-6%
70-90%
55-70%
Neutrophils are the most common type of white blood cell, making up 55-70% of the total white blood cell population in the average blood sample.
Example Question #345 : General Biology
Eosinophils make up what percent of the average white blood cell count?
1-3%
5-15%
20-40%
Less than 1%
1-3%
Eosinophils are the leukocytes that are largely responsible for response to parasitic infections and allergies. They make up 1-3% of the average white blood cell count. They form the second smallest population of white blood cells, after basophils, which normally make up less than 1% of white blood cells in whole blood.
Example Question #346 : General Biology
Monocytes make up what percent of the average white blood cell count?
26-33%
55-70%
2-10%
Less than 1%
2-10%
Monocytes, the largest of all the leukocytes, make up just 2-10% of the average white blood cell count. These white blood cells will mature into macrophages to phagocytose foreign matter.
Example Question #2 : Blood And Plasma
What is the role of macrophages in the immune response?
Antibody production
Phagocytosis of bacteria, cancer cells, and cellular debris
Release of histamine
Release of cytokines
Phagocytosis of bacteria, cancer cells, and cellular debris
Macrophages consume bacteria, cancer cells, and cellular debris via phagocytosis. Once these elements are within the cell, the macrophage is able to use lysosomes to break them down and prepare them for release into the blood as waste, which will eventually be excreted.
Example Question #347 : General Biology
What is the role of platelets in the blood?
Histamine release
Cytotoxicity
Clotting
Gas exchange
Clotting
Platelets are small cell fragments that play an important role in hemostasis, or clot formation. Once activated, platelets release clotting factors that recruit more platelets till a clot is formed and bleeding stops.
Example Question #344 : General Biology
The process by which white blood cells move into and out of blood vessels is __________.
Endocytosis
Diapedesis
Phagocytosis
Granulocytosis
Diapedesis
Diapedesis, also known as leukocyte extravasation, is the process by which white blood cells move into and out of blood vessels. This process includes four stages: chemoattraction, rolling adhesion, tight adhesion, and endothelial transmigration. This process is integral in the delivery of white blood cells to sites of infection and in their return into the blood stream to mobilize and facilitate the excretion of waste.