Question 1

What is the normal life span of a red cell in circulation?&#10;A)2 weeks&#10;B)90 days&#10;C)120 days&#10;D)6 months

Accepted Answer

The normal red cell survives 120 days in circulation after its release from the bone marrow.By that time,changes that have occurred both internally and on the RBC membrane result in its phagocytosis and thus removal by splenic macrophages.

Question 2

What important function does 2,3-BPG perform?&#10;A)maintains iron in the hemoglobin molecule in the ferrous state&#10;B)prevents oxidative injury to the red cell&#10;C)facilitates the delivery of oxygen to tissue&#10;D)aids in the exchange of membrane lipids with lipids in plasma

Accepted Answer

2,3-BPG plays a critical role in the effective transport of oxygen to tissue.It is produced via a shunt off the EMP.Elevations in 2,3-BPG are seen in a number of situations such as anemia;they result in more effective delivery of oxygen to tissue.It has no role in the other functions listed.

Question 3

What is the fate of erythrocytes when anaerobic metabolic enzymes are reduced in concentration or absent?&#10;A)destruction by the liver&#10;B)destruction by monocytes in the blood&#10;C)hemolysis&#10;D)destruction by complement

Accepted Answer

When metabolic enzymes in the anaerobic pathway of glycolysis are reduced or absent,energy production in the form ATP is diminished.This ultimately results in hemolysis of the RBC because the functions requiring energy in the form of ATP are not fully operational.This hemolysis occurs primarily in the spleen and so is called extravascular hemolysis (as opposed to occurring in the blood vessels,where it would be considered intravascular hemolysis).

Question 4

Why is the mature erythrocyte unable to synthesize proteins or lipids?&#10;A)It has no nucleus.&#10;B)It has no ribonucleic acid (RNA).&#10;C)It cannot generate adenosine triphosphate (ATP).&#10;D)Carrying oxygen interferes with synthesis.

Accepted Answer

The mature red cell no longer has a nucleus,mitochondria,and other organelles.It is therefore unable to synthesize proteins or lipids.It also cannot perform oxidative phosphorylation.

Question 5

Select the metabolic pathway that converts toxic hydrogen peroxide produced by oxidant drugs to water:&#10;A)Embden-Meyerhof pathway (EMP)&#10;B)2,3-biphosphoglycerate (2,3-BPG)&#10;C)methemoglobin reductase reaction&#10;D)hexose monophosphate pathway

Accepted Answer

Hydrogen peroxide is an oxidant and is detoxified via the hexose monophosphate pathway using reduced glutathione.The EMP generates energy in the form of ATP;the 2,3-BPG pathway is a shunt off of the EMP that is important for the reversible binding of oxygen.Methemoglobin reductase is an enzyme that reduces the oxidized form of hemoglobin,called methemoglobin,to its reduced functional form.

Question 6

Glucose-6-phosphate dehydrogenase (G6PD)is&#10;A)an extremely rare enzyme deficiency.&#10;B)necessary to maintain reduced glutathione in the mature red cell.&#10;C)important for the production of ATP in the mature red cell.&#10;D)important for the transport of carbon dioxide by the mature red cell.

Accepted Answer

G6PD is an enzyme in the hexose monophosphate pathway and is important for maintaining reduced glutathione in the red cell.This substance (reduced glutathione)is critical for preventing oxidative damage to red cell proteins.This pathway does not produce any energy and has no function in carbon dioxide transport.Its deficiency is very common worldwide,affecting millions of people;in fact,it is the most common human enzyme deficiency in the world.

Question 7

Which of the following is the metabolic pathway that generates a net gain of two molecules of ATP for erythrocyte energy needs?&#10;A)EMP&#10;B)2,3-BPG&#10;C)methemoglobin reductase reaction&#10;D)hexose monophosphate pathway

Accepted Answer

A net gain of two molecules of ATP occurs for every molecule of glucose metabolized via the EMP.When the 2,3-BPG shunt off of the EMP pathway is taken,no net gain of ATP occurs.No energy is generated via the hexose monophosphate pathway.The methemoglobin reductase reaction reduces methemoglobin,the oxidized form of hemoglobin,to its reduced functional form and does not generate energy.

Question 8

What is responsible for erythrocyte deformability and maintaining cell shape?&#10;A)membrane proteins&#10;B)Na+ and K+ pump&#10;C)membrane lipids&#10;D)Ca2+ pump

Accepted Answer

Proteins in the membrane are responsible for maintaining the shape and deformability of the red cell.Cation pumps maintain the Na⁺ and K⁺ gradient within the red cell.Membrane lipids form the fluid foundation into which the membrane proteins are inserted.The Ca²⁺ pump maintains intracellular levels of Ca²⁺.

Question 9

Which of the following is most responsible for the strength and pliancy of the red cell membrane?&#10;A)glycophorin A&#10;B)spectrin&#10;C)cholesterol&#10;D)ankyrin

Accepted Answer

Spectrin composes 50% to 70% of the membrane skeletal mass and is the primary peripheral protein involved in maintaining the skeletal structure of the red cell.By the way it lines up with other spectrin molecules,it also plays an important role in making the red cell membrane deformable (pliant).This flexibility is important for permitting the red cell to "squeeze" through pores that have a diameter smaller than that of the red cell.

Question 10

Which of the following erythrocyte activities requires energy?&#10;A)oxygen delivery&#10;B)carbon dioxide exchange&#10;C)glucose transport into the RBC&#10;D)protecting proteins from oxidative damage

Accepted Answer

Energy is required to protect proteins in the red cell from oxidative damage.This includes hemoglobin and membrane proteins.It is not required for oxygen transport,carbon dioxide exchange,or glucose transport into the cell.

Question 11

Which of the following is the metabolic pathway that regulates oxygen delivery to tissues?&#10;A)EMP&#10;B)2,3-BPG&#10;C)methemoglobin reductase reaction&#10;D)hexose monophosphate pathway

Accepted Answer

The answer of Which of the following is the metabolic...

Question 12

What components of the erythrocyte membrane are responsible for its negative charge and are also blood group antigens?&#10;A)peripheral proteins&#10;B)cholesterol&#10;C)cation pumps&#10;D)transmembrane proteins

Accepted Answer

The answer of What components of the erythrocyte membrane are...

Question 13

The principle energy source for mature red blood cells (RBCs)is&#10;A)the Krebs cycle.&#10;B)the hexose monophosphate pathway.&#10;C)ATP generated from anaerobic glycolysis.&#10;D)adenosine diphosphate (ADP) generated from aerobic glycolysis.

Accepted Answer

The answer of The principle energy source for mature red...

Deck 9: Erythrocyte Metabolism and Membrane Structure and Function