Lecture 8 Flashcards by Antonio Flamenco

What are the 3 main components to RBC survival?

RBC membrane
Hemoglobin structure and function
Cellular metabolism

How well did you know this?

Not at all

Perfectly

Red Cell Membrane

semipermeable lipid bilayer supported by a protein mesh-like cytoskeleton structure
Phospholipids, the main lipid components
Proteins that extend from the outer surface and span the entire membrane

How well did you know this?

Not at all

Perfectly

Glycophorin

the principal RBC glycoprotein (20% of the total membrane protein)
Four glycophorin (4) types : A, B, C, D

How well did you know this?

Not at all

Perfectly

What does glycophorin do?

carry the RBC antigens
serve as receptors, or transport proteins
anchor the plasma membrane envelop to the cytoskeleton network

How well did you know this?

Not at all

Perfectly

Are lipids distributed equally throughout the 2 layers of the membrane?

No they are not

How well did you know this?

Not at all

Perfectly

RBC Lipid Bilayer: Outer layer

rich in glycolipids and choline phospholipids
sphingomyelin and phosphatidlycholine

How well did you know this?

Not at all

Perfectly

RBC Lipid bilayer: Inner layer

rich in phosphatidlyserine, phosphatidylethanolamine (known as amino phospholipids), and phosphotidylinositol

How well did you know this?

Not at all

Perfectly

Biochemical composition of RBC membrane

52 percent protein
40 percent lipid
8 percent carbohydrate

How well did you know this?

Not at all

Perfectly

Normal lifespan of RBC

120 days

How well did you know this?

Not at all

Perfectly

What is a critical role in cell membrane

deformability and permeability

How well did you know this?

Not at all

Perfectly

What is freely permeable in a cell membrane?

Water
Anions (HCO3- and Cl-)
occurs through a large number of exchange channels

How well did you know this?

Not at all

Perfectly

What isn’t freely permeable in an RBC membrane?

Cations (Na and K)

How well did you know this?

Not at all

Perfectly

erythrocyte intracellular-to-extracellular ratios for sodium and potassium

1:12 (Na), respectively
25:1 (K), respectively

How well did you know this?

Not at all

Perfectly

How many pumps control the passive influx of Na and K?

300 cationic pumps

How well did you know this?

Not at all

Perfectly

What is needed for the cationic pumps for Na and K?

Needs energy like ATP
Also needs ATPase, a membrane enzyme

How well did you know this?

Not at all

Perfectly

What element is also actively transported from the interior of the RBC?

Calcium (C++)
through the energy-dependent calcium-ATPase cationic pump

How well did you know this?

Not at all

Perfectly

Calmodulin

cytoplasmic calcium-binding protein
speculated to control calcium-ATPase pumps
preventing excessive intracellular calcium buildup

How well did you know this?

Not at all

Perfectly

What happens with build of calcium?

shape changes and loss of deformability

How well did you know this?

Not at all

Perfectly

permeability properties of the RBC membrane

crucial to preventing colloid osmotic hemolysis
controlling the volume of the red cell

How well did you know this?

Not at all

Perfectly

What is the proper Osmotic pressure for RBCs?

300 mOs- considered Isotonic

How well did you know this?

Not at all

Perfectly

What are the other Osmotic pressures?

100 mOs- Hypotonic (Bloated)
500 mOs- Hypertonic (Shriveled)

How well did you know this?

Not at all

Perfectly

The energy required for active transport and maintenance of membrane electrochemical gradients is provided by what?

ATP

What is the metabolic Pathway of ATP for RBCs?

Anaerobic, because the function of the red cell is to deliver oxygen, not to consume it

How must energy be made in RBC? Why?

generated almost exclusively through the breakdown of glucose
Because mature erythrocytes have no nucleus and no mitochondria apparatus

What is done in RBC metabolism to maintain hemoglobin function?

divided among the anaerobic glycolytic pathway and three ancillary pathways For the sake of RBC structure and O2 transport

What is the main metabolic pathway of RBCs?

Glycolysis- Ninety percent of the ATP needed by RBCs is generated

What is the remaining ATP made from?

The remaining 10% ATP is provided by the pentose phosphate pathway

methemoglobin reductase

another important pathway are important in maintaining hemoglobin in a reduced functional state necessary to maintain the heme iron of hemoglobin in the ferrous (Fe++) functional state

Methemoglobin

form of the oxygen-carrying hemoglobin, in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) Can't carry O2

NADH

enzyme responsible for converting methemoglobin back to hemoglobin

What happens when NADH is low?

Methemoglobin accumulates loss of oxygen transport capabilities

Luebering-Rapaport shunt

permits the accumulation of another important red cell organic phosphate, 2,3-diphosphoglycerate (2,3-DPG)

2,3-diphosphoglycerate (2,3-DPG)

Found in one-to-one molar relationship with hemoglobin, representing approximately 5 mM profound effect on the affinity of hemoglobin for oxygen

What is essential for Hemoglobin Synthesis?

Adequate iron delivery and supply Adequate synthesis of protoporphyrins (the precursor of heme) Adequate globin synthesis

What is the most common Hemoglobin?

HbA, 92 to 95 percent of the hemoglobin

HbA composition

two alpha and two beta chains

HbA1c

3 to 5 percent of the hemoglobin Made of 2 alpha chains and 2 glucose chains

HbA2

2 alpha and delta chains 2-3% of the hemoglobin

HbF

Fetal Hemoglobin 1 to 2 percent of the hemoglobin two alpha and two gamma

What is hemoglobin's main function?

gas transport: oxygen delivery to the tissues and carbon dioxide (CO2) excretion

What is essential about 2,3-DPG?

most important controls of hemoglobin affinity for oxygen

Tense v Relaxed forms of hemoglobin

Tense has a low affinity Relaxed has a high affinity

How is the dissociation and binding of oxygen by hemoglobin represented

a sigmoid-curve relationship

The normal position of the oxygen dissociation curve depends on three different ligands normally found within the red cell

H+ ions CO2 organic phosphates (2,3-DPG)

Of the three ligands for O2 dissociation curve, which is most important?

2,3-DPG

shift to the right of curve

In situations such as hypoxia an decrease in hemoglobin-oxygen affinity and an increase in oxygen delivery to the tissues mediated by increased levels of 2,3-DPG

Aside from Hypoxia how can a right shift help?

a patient who is suffering from an anemia making the RBCs, although few in number, more efficient patients may be able to tolerate anemia

shift to the left of curve

an increase in hemoglobin-oxygen affinity and a decrease in oxygen delivery to the tissues

Reasons for left shift

Alkalosis increased quantities of abnormal hemoglobin's, such as methemoglobin and carboxyhemoglobin increased quantities of hemoglobin F; or multiple transfusions of 2,3-DPG

RED CELL PRESERVATION

provide viable and functional blood components for patients needing blood transfusion

How is RBC preservation done?

focused on maintaining red cell viability during storage and lengthening red cell posttransfusion survival

RBC Deformability

Loss of ATP increase in deposition of membrane calcium causing an increase in membrane rigidity and loss of pliability

RBC Deformability: signs

“spherocytes” (cells with a reduced surface-to-volume ratio) “bite cells” removal of a portion of membrane