Red Blood Cell Physiology Quiz

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Questions and Answers

What percentage of red blood cells are typically destroyed by the extravascular hemolysis process?

50%

80%

70%

90% (correct)

What primarily causes the aging of red blood cells leading to their destruction?

Increase in mitochondrial activity

Increase in cell size

Increase in ATP production

Decrease in membrane flexibility (correct)

Which process describes the decline in enzyme activity, particularly glycolysis, in aging red blood cells?

Necrosis

Senescence (correct)

Lysis

Apoptosis

What primarily happens to red blood cells during the culling process in the spleen?

They are filtered and destroyed Signup and view all the answers

What is the primary source of ATP production in mature red blood cells?

Glycolysis Signup and view all the answers

What happens to the concentration of hemoglobin in red blood cells as they age?

Increases Signup and view all the answers

What characteristic of aged red blood cells prevents them from passing through the splenic sieve?

Spherical rigidity Signup and view all the answers

What is the role of macrophages in the destruction of aged red blood cells?

They perform phagocytosis Signup and view all the answers

What percentage of RBC destruction is attributed to intravascular hemolysis according to Turgeon?

10 to 20% Signup and view all the answers

What is the primary consequence of fragmentation during intravascular hemolysis?

Hemoglobin is released into the bloodstream. Signup and view all the answers

What happens to plasma haptoglobin levels during hemolysis?

They decrease. Signup and view all the answers

What does excess unbound hemoglobin in the kidneys get converted into?

Urobilin Signup and view all the answers

What is oxidized hemoglobin converted to when it is not bound by haptoglobin?

Methemoglobin Signup and view all the answers

What transport protein is responsible for taking up heme groups released from methemoglobin?

Hemopexin Signup and view all the answers

What occurs once the renal tubular capacity for hemoglobin uptake is exceeded?

Free hemoglobin and methemoglobin appear in urine. Signup and view all the answers

What complex is formed when heme groups exceed hemopexin-binding capacity?

Hemopexin-albumin Signup and view all the answers

What is the most common enzyme deficiency associated with glycolysis?

Pyruvate kinase deficiency Signup and view all the answers

Which pathway couples oxidative catabolism of glucose with reduction of NADP to NADPH?

Pentose phosphate pathway Signup and view all the answers

What is the effect of increased oxidation of glutathione on the pentose phosphate pathway?

Increases the pathway's activity Signup and view all the answers

What is the condition of hemoglobin when heme iron is oxidized to ferric state?

Methemoglobin Signup and view all the answers

What is the primary function of reduced glutathione (GSH) in red blood cells?

Prevents oxidative denaturation of hemoglobin Signup and view all the answers

Which pathway generates 2,3 Diphosphoglycerate (2,3-DPG)?

Rapaport Luebering pathway Signup and view all the answers

What does methemoglobin reductase enzyme do?

Reduces ferric iron back to ferrous state Signup and view all the answers

What implications does G6PD deficiency have on erythrocytes?

Increased oxidative damage susceptibility Signup and view all the answers

What is the first stage of hemoglobin synthesis?

Rubricyte Signup and view all the answers

Which of the following is the last stage capable of hemoglobin synthesis?

Reticulocyte Signup and view all the answers

Where does heme synthesis occur in normoblasts?

Mitochondria Signup and view all the answers

Which chromosomes control globin synthesis?

Chromosome 11 and 16 Signup and view all the answers

How is the oxygen dissociation curve described?

S-shaped Signup and view all the answers

What effect does a lower pH have on hemoglobin's affinity for oxygen?

Decreases affinity Signup and view all the answers

In the context of the P50 value, what does it indicate?

Amount of oxygen needed to saturate 50% hemoglobin Signup and view all the answers

What is the Bohr effect?

Change in Hb affinity due to pH Signup and view all the answers

What is the primary effect of carbon monoxide on hemoglobin?

Reduces oxygen carrying capacity Signup and view all the answers

What color does carbon monoxide impart to the blood?

Bright cherry red Signup and view all the answers

Which of the following is essential for iron to bind to hemoglobin?

Ferrous state (Fe2+) Signup and view all the answers

What is the role of DMT in iron metabolism?

Transport of dietary iron into enterocytes Signup and view all the answers

How much iron is typically absorbed from a normal daily diet?

1-2 mg Signup and view all the answers

What is the primary regulatory hormone of systemic iron metabolism?

Hepcidin Signup and view all the answers

Where is most of the body's iron found?

In hemoglobin Signup and view all the answers

Which form of iron is not able to bind to hemoglobin?

Ferric iron (Fe3+) Signup and view all the answers

Study Notes

Erythrocytes and Red Blood Cell Destruction

Erythrocytes (red blood cells) undergo senescence, characterized by decreased enzyme function, ATP depletion, reduced size, and increased density.
Mature erythrocytes lack nuclei and cannot regenerate proteins, leading to functional decline and eventual death; lifespan averages 120 days.
RBCs rely exclusively on glycolysis for ATP production due to the absence of mitochondria.
Aging RBCs undergo phagocytosis, with approximately 1% leaving circulation daily, predominantly handled by the mononuclear phagocytic system.
The spleen performs culling, filtering out aged RBCs through macrophage phagocytosis.

Types of RBC Destruction

Extravascular Hemolysis:
- Primary method of normal RBC death, responsible for a significant portion of destruction.
- Requires flexibility for RBCs to pass through splenic sieve; rigid cells become trapped and phagocytized by macrophages.
Intravascular Hemolysis:
- Accounts for a smaller percentage (10-20%) of RBC destruction, occurring in peripheral circulation due to mechanical factors.
- Results in hemoglobin release into the bloodstream, dissociated into dimers which bind plasma globulin.

Hemolysis Mechanisms

Haptoglobin binds hemoglobin for hepatic removal; depletion leads to filtered and reabsorbed hemoglobin in kidneys.
Excess hemoglobin not bound to haptoglobin is converted to methemoglobin and heme groups associate with transport proteins like hemopexin.

Glycolysis: Primary energy production pathway in RBCs.
Pentose Phosphate Pathway: Generates NADPH for glutathione reduction, protecting erythrocytes from oxidative damage; G6PD deficiency is common and associated with Heinz bodies.
Methemoglobin Reductase Pathway: Converts ferric hemoglobin back to its ferrous state, crucial for oxygen transport.
Rapaport Luebering Pathway: Produces 2,3-DPG which decreases hemoglobin's oxygen affinity, aiding gas exchange.

Heme Synthesis

Heme synthesis depends on biochemicals like glycine and vitamin B6, occurring in mitochondria.
Globin synthesis relies on genetic coding from chromosomes 16 and 11.

Oxygen Dissociation Curve (ODC)

Illustrates the relationship between oxygen saturation of hemoglobin and the partial pressure of oxygen; typically sigmoidal in shape.
P50 indicates oxygen tension required for 50% saturation of hemoglobin.
The Bohr effect describes how lower pH enhances oxygen release in tissues via rightward shift of the curve.
Carbon monoxide binding to hemoglobin reduces its oxygen-carrying capacity, causing leftward shift on the ODC and increased blood color.

Iron Metabolism

Iron is vital, mainly existing in hemoglobin and must be in ferrous (Fe2+) state for effective transport; ferric (Fe3+) cannot bind hemoglobin.
Daily intake of iron is about 15mg, with 1-2mg absorbed primarily in the duodenum; iron transport is mediated by DMT (Divalent Metal Transporter).
Iron can be stored as ferritin in enterocytes or exported via Fpn1 (Ferroportin).
Transferrin, produced in the liver, regulates systemic iron metabolism, facilitating delivery to cells through transferrin receptors.

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Description

Test your knowledge on the physiology of red blood cells! This quiz covers the causes of aging in red blood cells, processes involved in their hemolysis, and changes in enzyme activity. Understanding these concepts is crucial for comprehending how red blood cells function and ultimately perish within the body.