Red Blood Cell Biology
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Which characteristic of the red blood cell membrane is most critical for its role in oxygen delivery?

  • Its complete lack of proteins.
  • Its impermeability to all substances, ensuring no leakage.
  • Its rigid structure that prevents deformation.
  • Its semipermeable nature, allowing selective passage of molecules. (correct)

What structural feature provides support to the red blood cell membrane?

  • A rigid lipid monolayer.
  • A thick layer of cholesterol.
  • A wall of tightly packed integral proteins.
  • A meshlike protein cytoskeleton structure. (correct)

What is a key characteristic of integral membrane proteins in red blood cells?

  • They are loosely attached to the inner surface of the membrane.
  • They span the entire phospholipid bilayer, with both extracellular and intracellular domains. (correct)
  • They are composed of lipids rather than amino acids.
  • They are small and located only on the outer surface of the membrane.

Which of the following is NOT typically classified as a peripheral protein associated with the red blood cell membrane?

<p>Spectrin (D)</p> Signup and view all the answers

How do integral membrane proteins contribute to the function of red blood cells beyond structural support?

<p>By facilitating cell signaling and transport of specific molecules. (D)</p> Signup and view all the answers

What is the primary role of Calmodulin in maintaining red blood cell (RBC) health?

<p>To prevent excessive buildup of intracellular Ca2+, maintaining RBC shape and flexibility. (A)</p> Signup and view all the answers

How does ATP depletion in RBCs contribute to decreased RBC survival?

<p>ATP depletion causes an imbalance in ion concentrations, leading to dehydration and rigidity, making them susceptible to splenic sequestration. (B)</p> Signup and view all the answers

What is the primary benefit of the pentose phosphate pathway in red blood cells (RBCs)?

<p>It prevents oxidative damage by managing reactive oxygen species. (D)</p> Signup and view all the answers

In ATP-depleted red blood cells, which of the following ionic imbalances primarily contributes to cell rigidity?

<p>Increased intracellular calcium (Ca2+) and sodium (Na+), and decreased intracellular potassium (K+). (D)</p> Signup and view all the answers

How do red blood cells (RBCs) maintain a delicate balance to ensure their survival and function?

<p>Through a combination of balanced pumps, energy supply, electrolyte concentrations, and water content. (A)</p> Signup and view all the answers

What structural feature of the red blood cell (RBC) membrane directly contributes to its characteristic biconcave shape?

<p>The meshwork beneath the phospholipid bilayer in the cytoplasmic compartment. (C)</p> Signup and view all the answers

Which of the following is a primary function of the red blood cell (RBC) membrane's extracellular domains?

<p>Expressing specific blood group antigens through glycosylation. (A)</p> Signup and view all the answers

How do Glycophorin C and Band 3 proteins contribute to the structural integrity of the red blood cell (RBC) membrane?

<p>By attaching the cytoskeletal protein network to the cell membrane. (B)</p> Signup and view all the answers

How would disrupting the interaction between Glycophorin C and the cytoskeletal protein network likely affect a red blood cell (RBC)?

<p>Loss of biconcave shape. (D)</p> Signup and view all the answers

What is the primary role of phospholipids in the red blood cell (RBC) membrane?

<p>To form a bilayer that acts as a barrier. (D)</p> Signup and view all the answers

Where are peripheral proteins located in a red blood cell (RBC)?

<p>Loosely associated with the inner surface of the cell membrane. (D)</p> Signup and view all the answers

Which component of the red blood cell (RBC) membrane is responsible for interacting with both the intracellular and extracellular environments?

<p>Glycophorins (C)</p> Signup and view all the answers

If a drug were designed to prevent glycosylation of proteins on red blood cells (RBCs), which of the following functions would be most directly affected?

<p>Expression of blood group antigens (B)</p> Signup and view all the answers

In a patient experiencing metabolic acidosis due to severe sepsis, which of the following compensatory mechanisms would be expected to shift the oxygen dissociation curve?

<p>Hyperventilation to decrease $PCO_2$, leading to alkalosis. (C)</p> Signup and view all the answers

A pregnant woman at term is experiencing mild pre-eclampsia, leading to slightly reduced placental blood flow. How does fetal hemoglobin (HbF) compensate for potentially reduced oxygen delivery compared to adult hemoglobin (HbA)?

<p>HbF facilitates oxygen delivery from the mother to the baby. (D)</p> Signup and view all the answers

A mountain climber ascends rapidly to a high altitude, leading to a decrease in the partial pressure of oxygen in their blood. What immediate physiological change helps to maintain oxygen delivery to the tissues despite the lower oxygen availability?

<p>A shift of the oxygen dissociation curve to the right, promoting oxygen unloading at the tissues. (D)</p> Signup and view all the answers

A patient with chronic obstructive pulmonary disease (COPD) has chronically elevated levels of carbon dioxide in their blood ($PCO_2$). How does this condition affect the oxygen-hemoglobin dissociation curve and oxygen delivery to tissues?

<p>It induces the Bohr effect, resulting in a rightward shift, which enhances oxygen unloading in tissues. (B)</p> Signup and view all the answers

How does decreased tissue oxygen delivery related to reduced hemoglobin-oxygen affinity impact patients?

<p>Less oxygen is available/delivered to peripheral tissues. (C)</p> Signup and view all the answers

How does decreased RBC deformability affect red blood cell survival?

<p>It leads to blockage of sinusoids or destruction of RBCs, decreasing their survival. (B)</p> Signup and view all the answers

What is the primary role of cation transport systems in RBCs?

<p>To control the volume of the RBC. (B)</p> Signup and view all the answers

How does the semi-permeable nature of the RBC membrane contribute to the cell's function?

<p>It requires the RBC membrane to adapt to certain conditions to maintain its shape. (A)</p> Signup and view all the answers

Why are abnormalities in cationic transport detrimental to RBC survival?

<p>They lead to aberrations in RBC shape, causing faster destruction. (A)</p> Signup and view all the answers

What role do glycophorins play in the context of blood banking?

<p>Their glycosylated extracellular domains carry RBC antigens, such as ABO antigens. (C)</p> Signup and view all the answers

Predict what would happen if a drug increased the rate at which RBCs become permeable to sodium ions, without affecting other transport mechanisms.

<p>The RBCs would swell and potentially lyse due to water inflow. (A)</p> Signup and view all the answers

How does ATP contribute to RBC survival, considering the information provided?

<p>It regulates cation transport systems necessary for maintaining RBC volume. (C)</p> Signup and view all the answers

A patient's RBCs are found to have a reduced ability to synthesize ATP. Which of the following consequences is most likely?

<p>Disrupted cation transport leading to altered cell volume and premature destruction. (C)</p> Signup and view all the answers

What cellular event is most likely to occur if the sodium-potassium pumps in red blood cells fail?

<p>Cellular swelling and eventual lysis. (D)</p> Signup and view all the answers

How does 2,3-DPG affect hemoglobin's affinity for oxygen?

<p>Decreases oxygen affinity by stabilizing the T form. (D)</p> Signup and view all the answers

Which condition would cause a decrease in hemoglobin's affinity for oxygen, promoting oxygen release to tissues?

<p>Increased PCO2 (A)</p> Signup and view all the answers

A patient with a fever has an elevated body temperature. How would this condition be expected to affect the oxygen-hemoglobin dissociation curve and oxygen delivery to tissues?

<p>Shift the curve to the right, increasing oxygen delivery. (A)</p> Signup and view all the answers

What metabolic pathway provides the majority of ATP required by red blood cells?

<p>Glycolysis (B)</p> Signup and view all the answers

How does the Luebering-Rapaport shunt contribute to the function of red blood cells?

<p>By generating 2,3-DPG. (B)</p> Signup and view all the answers

If a patient is experiencing alkalosis -- a state of high blood pH --, how would this affect the oxygen-hemoglobin dissociation curve and oxygen delivery to tissues?

<p>Shift the curve to the left, decreasing oxygen delivery. (B)</p> Signup and view all the answers

When hemoglobin transitions from its deoxygenated to oxygenated state, what structural change occurs concerning 2,3-DPG?

<p>2,3-DPG is expelled, promoting the R form. (A)</p> Signup and view all the answers

Flashcards

RBC Membrane

The semipermeable covering of red blood cells, essential for their function.

Integral Membrane Proteins

Large proteins extending across the RBC membrane, crucial for various functions.

Semipermeable Membrane

Allows certain substances to pass in and out of the RBC.

RBC Cytoskeleton

A mesh-like protein structure supporting the RBC membrane.

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O2-Hgb Dissociation Curve

Illustrates how oxygen binds and releases from hemoglobin based on conditions.

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Calmodulin

A protein that regulates intracellular calcium levels in RBCs.

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Pentose Phosphate Pathway

A metabolic pathway that generates NADPH and ribose 5-phosphate while preventing oxidative damage.

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Reactive Oxygen Species (ROS)

Highly reactive molecules that can damage cells, including RBCs, produced in glycolysis.

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RBC Dehydration

Occurs when ATP depletion leads to loss of K+ and water, making RBCs rigid and prone to destruction.

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Glycolysis by-products

Products of glycolysis, some are harmful and can cause oxidative damage to RBCs.

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RBC Antigens

Molecules on RBCs that trigger immune responses, e.g., ABO blood groups.

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Deformability of RBCs

The ability of red blood cells to change shape when passing through narrow spaces.

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RBC Permeability

The capacity of the RBC membrane to selectively allow substances in and out.

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Cation Transport Systems

Mechanisms in RBCs that control the movement of ions, requiring ATP energy.

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RBC Volume Control

Regulated by cation transport systems to maintain red blood cell stability.

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ATP in RBCs

Adenosine triphosphate, the energy source for numerous RBC processes.

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Metabolic Pathways in RBCs

Processes through which red blood cells generate energy to function.

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RBC Shape Abnormalities

Alterations in red blood cell shape can reduce their survival in circulation.

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Phospholipid Bilayer

The fundamental structure of cell membranes, consisting of hydrophilic heads and hydrophobic tails.

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Extracellular Domain

The region of membrane proteins that extends outside the cell, often glycosylated.

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Glycosylation

The process of adding carbohydrates to proteins, common in extracellular domains.

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Glycophorins

A family of integral membrane proteins on RBCs, involved in antigen expression.

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Band 3 Protein

An integral protein in RBC membranes that helps transport bicarbonate and anchors other proteins.

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Cytoskeletal Framework

A network of proteins beneath the membrane that provides structure and support to RBCs.

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Peripheral Proteins

Proteins located on the inner surface of the membrane, associated with the cytoskeleton.

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Hemoglobin F

A type of hemoglobin that aids oxygen transfer from mother to baby.

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R Form of Hemoglobin

The relaxed form of hemoglobin with a higher affinity for oxygen.

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Shift to the Left

A curve shift indicating increased hemoglobin affinity for oxygen under certain conditions.

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Shift to the Right

A curve shift indicating decreased hemoglobin affinity for oxygen, typically in hypoxia.

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Respiratory Movement

Allosteric changes in hemoglobin as it binds and releases oxygen.

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2,3-DPG

An organic phosphate in RBCs that regulates hemoglobin's oxygen affinity.

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Oxygen loading

Process when hemoglobin binds oxygen in the lungs.

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Oxygen unloading

Release of oxygen from hemoglobin to the tissues.

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Tense (T) form of Hemoglobin

State of hemoglobin when it has low affinity for oxygen due to 2,3-DPG.

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Salt bridges

Ionic bonds between hemoglobin chains that affect oxygen binding.

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Factors decreasing O2 affinity

Conditions like high temperature and PCO2 that promote oxygen release.

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Factors increasing O2 affinity

Conditions such as low 2,3-DPG and low temperature that promote oxygen binding.

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Biconcave shape importance

Optimal shape for RBCs that enhances oxygen transport and flexibility.

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Study Notes

Red Blood Cell (RBC) Membrane

  • The RBC membrane is a complex structure, essential for functions like oxygen transport.
  • It's semipermeable, allowing substances to pass in and out of the cell.
  • Supported by a protein cytoskeleton.
  • The membrane is primarily composed of a phospholipid bilayer.
  • The bilayer has hydrophilic heads (water-loving) facing outwards and hydrophobic tails (water-fearing) facing inwards.

Integral Membrane Proteins

  • These proteins span the entire RBC membrane.
  • Have extracellular and intracellular domains.
  • Often glycosylated (carrying sugars), which can express blood group antigens.
  • Two major families: Glycophorins (A, B, C) and Band 3 proteins.
  • Glycophorins attach to the cytoskeleton, communicating with peripheral proteins, which are inside the cell.
  • Band 3 binds hemoglobin and anchors other peripheral proteins to the inner membrane surface.

Peripheral Membrane Proteins

  • Located on the inner surface of the RBC membrane.
  • Form part of the cytoskeleton, a mesh-like structure providing support and shape.
  • The cytoskeleton includes Spectrin, Actin, Band 4.1 protein, adducin, band 4.9 protein, and tropomyosin.
  • The cytoskeleton is dynamic, rearranging to maintain RBC shape during movement.
  • Peripheral proteins anchor to integral proteins, like Band 3 and Glycophorins.

RBC Deformability

  • RBCs must be deformable to pass through narrow blood vessels.
  • The cytoskeleton allows the cell to change shape without rupture.
  • Spectrin phosphorylation, ATP, and calcium levels play key roles in deformability.
  • Decreased deformability can lead to RBC destruction.

RBC Permeability

  • Semipermeable, meaning certain substances can pass through the membrane selectively.
  • The cell membrane controls the movement of ions (e.g., sodium, potassium) and water.
  • Ion pumps maintain ion concentration gradients.
  • Maintaining shape and volume of the cell requires energy.

RBC Metabolism

  • RBCs produce energy mainly anaerobically (without oxygen) via the glycolytic pathway.
  • The pentose phosphate pathway and methemoglobin reductase pathway also contribute to cellular function.
  • The Luebering-Rapaport shunt is important for creating and maintaining 2,3-DPG, a key regulatory molecule for hemoglobin.

Oxygen-Hemoglobin Dissociation Curve

  • Shows the relationship between oxygen partial pressure and hemoglobin saturation.
  • The sigmoidal shape facilitates oxygen uptake in the lungs and release in the tissues.
  • Factors like temperature, pH, CO2, and 2,3-DPG shift the curve, influencing hemoglobin's affinity for oxygen.
  • Shifts to the left mean greater oxygen affinity, while shifts to the right indicate lower affinity, delivering oxygen more easily to tissues.

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RBC Membrane Lecture Notes PDF

Description

This quiz focuses on the characteristics and functions of red blood cells including membrane structure, integral and peripheral proteins, ATP's role in cell survival, and the pentose phosphate pathway. It covers key aspects of RBC physiology and their crucial function in oxygen delivery.

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