RBC Structure Flashcards
What does a cytoskeleton do for a RBC?
Provides RBCs with strength & flexibility needed to survive in circulation
What are three things that are crucial to normal RBC survival & function?
- RBC membrane
- hemoglobin structure & function
- RBC metabolic pathways
What is deformability in a RBC?
Highly elastic
Can distort to traverse small capillaries
What does the RBC membrane let in?
Selectively sequesters vital components
What does the RBC membrane let out?
Allows escape of metabolic waste products
How does the RBC membrane regulate metabolism?
Reversibly binding & inactivating many glycolytic enzymes
How does the RBC membrane exchange bicarbonate & chloride ions?
Aids in transfer of carbon dioxide from tissues to lungs
Balances cation & water concentrations to maintain RBC ionic composition
What are the components and their percentages of the phospholipid bilayer-protein complex?
40% lipids
52% proteins
8% carbohydrates
What functions does the membrane control?
Transport
Durability/strength
Flexibility
The membrane composition determines the membrane’s what?
Antigenic properties
Defects in the membrane can alter function and lead to what?
Cell death
What are two major proteins of RBCs?
Glycophorin
Spectrin
What type of protein is glycophorin?
Integral protein
What type of protein is spectrin?
Peripheral protein
What does glycophorin account for?
Most of the negative net charge of RBC causing them to repel each other
What do glycophorins function as?
Anion exchange channels & glycophorins anchor the bilayer to the cytoskeleton
What is the major component of red cell skeleton?
Spectrin
What does spectrin do?
Attaches to other components such as ankyrin to form a network of microfilaments on the inner surface of the RBC
What does the network of microfilaments on the inner surface of the RBC do?
Strengthens the membrane & control biconcave shape & deformability of the cell
Spectrin is phosphorylated by a protein kinase in what kind of fashion?
ATP dependent
What are other types of peripheral proteins that are components of the cytoskeleton?
Ankyrin
Adducin & Band 4.1
Band 3
What does ankyrin do?
Couples lipid bilayer to the cytoskeleton
What does Adducin & Band 4.1 do?
Promotes the association of spectrin with F-actin
What is Band 3 and what does it do?
Integral protein
Catalyzes chloride-bicarbonate exchange & contains binding sites for ankyrin, band 4.1, etc.
RBC’s deformability is due to what?
Biconcave shape
Viscosity of it’s internal contents
Viscoelastic properties of the erythrocyte membrane
Deformability is necessary for what?
Small vessel transit
How does the loss of ATP affect spectrin?
Loss of deformability
Increased calcium deposists make RBC what?
Rigid
When RBCs are rigid what kind of cells do they become?
Bite cells & spherocytes
Where are bite cells & spherocytes removed prematurely?
In the spleen
Skeletal proteins are not what?
Static
Proteins are in equilibrium with each other and attachment sites through what two aspects?
Association & disassociation
Skeletal proteins are not static in response to what?
Various physical & chemical stimuli as RBCs travel through the body
What dimeric cell membrane protein is important in deformability & requires ATP?
Spectrin
RBCs are permeable to what compounds or elements?
Water
Cl-
HCO3-
Glucose
RBC are relatively impermeable to what?
Na & K
What are the exchange numbers for the ATPase Na/K pump?
2 K into cell & 3 Na out
When ATP depleted cells build up excess Na & lose water & K what happens?
Increased intracellular monovalent cations & water
Cell swelling & osmotic hemolysis
What is pumped out by the Ca-ATPase cationic pump?
Ca2+
Why is Ca2+ is pumped out?
To maintain low levels of intracellular Ca2+
Elevated Ca2+ induces membrane protein cross-linking how?
Acting as a fixative
Causing less shape changes & a loss of deformability
What are some RBC membrane lipids?
Phospholipds
Glycolipids
Cholesterol
An altered arrangement of phospholipids can result in activation of clotting & can lead to what?
Extravascular hemolysis
Where are glycolipids located in the RBC membrane?
Outer half of lipid membrane
What do glycolipids do in the RBC membrane?
Interact with glycoproteins to form many RBC antigens
When there is excess cholesterol in the RBC membrane what happens?
There is less fluidity in the cell membrane
What two deficiencies may produce acanthocytes & cell hemolysis?
Abetalipopprteinemia & LCAT deficiency
Excess cholesterol does what to RBCs?
Changes morphology - target cells & acanthocytes
RBC membrane damage
Excess cholesterol can cause red blood cells to become what?
Target cells & acanthocytes
Cholesterol accumulation in the RBC membrane causes what RBC morphology?
Target cells
Abetalipoproteinemia with cholesterol accumulation causes what type of RBC morphology?
Acanthocytes
LCAT deficiency causes what RBC morphology?
Hemolysis with red cell fragmentation
Decreased phosphorylated spectrin or altered spectrin causes what type of RBC morphology?
Bite cells & spherocytes
What protein is a heterodimer that is important in RBC cytoskeleton?
Spectrin
What shape is an acanthocyte cell?
Helmet shape
