Ch. 9 - RBC Membrane Flashcards by Zean Earl Carpeso

RBC deformability depends on _____, _____, and _____.

RBC geometry
Cytoplasmic (hemoglobin) viscosity
Membrane elasticity (pliancy)

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RBCs have an average of 90fL volume and 140 um^2 surface area, a 40% excess of surface area. This excess surface-to-volume ratio enables RBCs to stretch undamaged up to ___ times their resting diameter.

2.5

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What is the normal range value of mean cell hemoglobin concentration?

32% to 36%

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As concentration rises, viscosity (rises, decreases, does not change)

Rises

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Hemoglobin concentrations above ___% compromise deformability and shorten the RBC life span, because the more viscous cells cannot accommodate to narrow capillaries or splenic pores

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RBCs with high concentrations of hemoglobin and therefore cannot pass through the splenic pores, is destroyed by _____.

Splenic macrophages

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The RBC membrane consists of approximately:
___% carbohydrates
___% proteins
___% lipids

8
52
40

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This portion of the RBC membrane is composed of equal parts or cholesterol and phospholipids and forms a bilayer universal to all animal cells.

Lipid portion

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What are the two parts of the bilayer formed in the RBC membrane?

Hydrophilic polar head groups

Hydrophobic non-polar acyl tail

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This is esterified and largely hydrophobic and resides parallel to the acyl tails of the phospholipids. This confers tensile strength to the lipid bilayer.

Cholesterol

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The only hydrophilic portion of cholesterol molecule; this anchors within the polar head groups l, while the rest of the molecule intercalates among and parallel to the acyl tails

Cholesterol B (beta) hydroxyl group

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These enzymes maintain the cholesterol concentration by regularly exchanging membrane and plasma cholesterol.

Membrane enzymes

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As cholesterol rises, the membrane (gains/loses) strength but (gains/loses) elasticity

Gains

Loses

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What are the four main phospholipids found in the bilayer?

Sphingomyelin
Phosphatidylcholine
Phosphatidylserine (PS)
Phosphatidylethanolamine

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What phospholipids are found mostly in the outer layer of the bilayer?

Sphingomyelin

Phosphatidylcholine

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What phospholipids are found mostly in the inner layer of the bilayer?

Phosphatidylserine (PS)

Phosphatidylethanolamine

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Distribution of the phospholipids is energy dependent, relying on a number of membrane-associated enzymes called _____, _____, and _____..

Flippases
Floppases
Scramblases

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The only negatively charged phospholipid; redistributes (flips) to the outer layer when phospholipid distribution is disrupted.

Phosphatidylserine (PS)

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Enumerate instances wherein phospholipid distribution is disrupted.

Sickle cell anemia
Thalassemia
RBCs that have reached the end of their 120-day life span

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What type of macrophages possess receptors that bind phosphatidylserine (PS) and destroys senescent RBCs?

Splenic macrophages

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These are sugar bearing lipids that make up 5% of the external half of the RBC membrane.

Glycolipids

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They associate in clumps or rafts and support carbohydrate side chains that extend into the aqueous plasma to help form the glycocalyx.

Glycolipids

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This is a layer of carbohydrates whose net negative charge prevents microbial attack and protects the RBC from mechanical damage caused by adhesion to neighboring RBCs or to the endothelium.

Glycocalyx

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These two types of RBC membrane proteins make up 52% of the membrane structure by mass.

Transmembranous (integral)

Skeletal (cytoskeletal, peripheral)

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A type of membrane protein that, through glycosylation, supports surface carbohydrates, which join with glycolipids to make up the protective glycocalyx.

Transmembranous proteins

A type of membrane protein that serve as transport and adhesion sites and signaling receptors.

Transmembranous proteins

Any disruption in transport protein function changes the osmotic tension of the cytoplasm, which leads to a (rise/decrease) in viscosity and (increase/loss) of deformability.

Rise | Loss

This is the process wherein signaling receptors bind plasma ligands and trigger energy activation of submembranous G proteins that then initiate various energy-dependent cellular activities.

Signaling transduction

The transmembranous proteins assemble into two macromolecular complexes named by their respective skeletal anchorages. These are the _____ and _____. These complexes and their anchorages provide RBC membrane structural integrity.

Ankyrin | Protein 4.1

The transmembranous protein that functions for anion transport and supports the majority of ABH system carbohydrate determinants

Band 3

The transmembranous protein that functions for glucose transport and supports the majority of ABH system carbohydrate determinants

Glut-1

Enumerate two transmembranous proteins that supports the majority of ABH system carbohydrate determinants

Band 3 | Glut-1

Enumerate some trnasmembranous proteins that provide peptide epitopes.

Glycophorin A | Glycophorin B

The transmembranous protein that carries the peptide-defined M and N determinants

Glycophorin A

The transmembranous protein that carries the Ss determinants

Glycophorin B

Comprise the MNSs system

M and N determinants | Ss determinants

Loss of this glycoprotein prevents expression of both the D and CcEd antigen (Rh null) and is assocoiated with morphologic RBC abnormalities.

RhAG

These serve as anchors for two surface proteins, decay accelerating factor (DAF or CD55) and membrane inhibitor of reactive lysis (MIRL or CD59).

Phosphatidylinositol (PI)

What are the two surface proteins anchored by the Phosphatidylinositol (PI)?

Decay Accelerating factor (DAF or CD55) | Membrane inhibitor of reactive lysis (MIRL or CD59)

What links the accelerating factor (DAF or CD55) and membrane inhibitor of reactive lysis (MIRL or CD59) to Phosphatidylinositol (PI)? It is a glycan core consisting of multiple sugars.

Phosphatidylinositol glycan class-A (PIG-A)

It is a condition wherein the PIG-A requires a mutation, CD55 and CD59 become deficient, and the cell is susceptible to complement mediated hemolysis

Paroxysmal nocturnal hemoglobinuria

Numerical naming derives from historical protein identification techniques that distinguishes 15 membrane proteins using _____.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)

Give the two principal skeletal proteins that assemble to form an antiparallel heterodimer held together with a series of lateral bonds

a(alpha)-spectrin | B(beta)-spectrin

This term means that the carboxyl (COOH) end of one strand associates with the amino (NH3) end of the other.

Antiparallel

Skeletal proteins are also called _____ because they do not penetrate the bilayer.

Peripheral proteins

The secondary structure of both a(alpha)-spectrin an B(beta)-spectrin features _____ of 106 amino acids; 20 such repeats make up a(alpha)-spectrin and 16 make up B(beta)-spectrin.

Triple-helical repeats

Enumerate skeletal proteins essential to the cytoskeleton.

``` Ankyrin Protein 4.1 Adducin Dematin Actin Tropomyosin Tropomodulin ```

Autosomal dominant mutations that affect the integrity of band 3, RhAG, ankyrin, protein 4.1, or spectrin are associated with what condition? In these cases, there are too few vertical anchorages to maintain membrane stability.

Hereditary spherocytosis

Enumerate some skeletal proteins affected byhHereditary spherocytosis

``` Band 3 RhAG Ankyrin Protein 4.1 Spectrin ```

In Hereditary spherocytosis, the lipid membrane peels off in small blebs [a rounded outgrowth on the surface of a cell] called _____, whereas the cytoplasmic volume remains intact.

Vesicles

This condition arises from one of several autosomal dominant mutations affecting spectrin dimer-to-dimer lateral bonds or the spectrin-ankyrin-protein 4.1 junction.

Hereditary elliptocytosis

In this condition, the membrane fails to rebound from deformation, and RBCs progressively elongate to form visible elliptocytes, which causes a mild to severe hemolytic anemia

Hereditary elliptocytosis

The RBC membrane is impermeable to what elements?

Na+ K+ Ca2+

Aside from water, the RBC membrane is permeable to what elements?

Anions bicarbonate (HCO3-) and Chloride-

This is a transmembranous protein that forms pores or channels whose surface charges create inward flow of water in response to internal osmotic changes.

Aquaporin 1

What transmembranous protein transports glucose without energy expenditure?

Glut-1

These regulates the concentrations of Na+ and K+, maintaining intracellular-to-extracellular ratios of 1:12 and 25:1 respectively.

Adenosine triphosphatase (ATPase)-dependent (energy dependent) cation pumps

What is the intracellular-to-extracellular ratio of Na+?

1:12

What is the intracellular-to-extracellular ratio of K+?

25:1

These enzyme-based pump mechanisms, in addition to aquaporin, maintain osmotic balance.

Adenosine triphosphatase (ATPase)-dependent (energy dependent) cation pumps

It is known as the phenomenon wherein the cell swells, becomes spheroid, and eventuallyruptures, spilling hemoglobin.

Colloid osmotic hemolysis

Ca2+ ATPase extrudes [thrust or force out] calcium, maintaining exceptionally low intracellular levels of ___ to ___ umol/L.

5 to 10

This is a cytoplasmic Ca2+-binding protein that controls the function of Ca2+ ATPase

Calmodulin

This disease provides an example of increased cation permeability.

Sickle cell disease

When crystallized sickle hemoglobin deforms the cells, internal levels of Na+, K+, and especially Ca2+ rise. This results in _____.

Hemolysis

The glycoporins, with abundant carbohydrate side chains, are stained using what type of dye?

Periodic acid-Schiff (PAS) Dye

ATP is generated by the (EMP/HMP/LRP/Aerobic glycolytic pathway)

Embden-Meyerhof pathway

The activity of the Hexose Monophosphate pathway increases the RBC source of _____.

NADPH and reduced glutathione

The layer of the cell that is largely responsible for the dpshape, structure, and deformability of the cell is the _____.

Peripheral protein layer

The numbering system for membrane proteins give the lowest number to proteins that are (smallest/most negative/largest/most positive).

Largest