Erythrocyte Structure and Function: Topic 1 Flashcards
what are the three main types of cells in the blood?
- erythrocytes (RBC)
- leukocytes (WBC)
- thrombocytes (platelets)
why are RBCs red?
Hb in RBC contains iron that creates a red pigment when it binds to oxygen
what is the function of RBCs?
they reversibly bind oxygen and carbon dioxide to deliver oxygen to the tissues and to remove carbon dioxide in the lungs
this reversible binding creates a difference in oxygen content between venous and arterial blood; therefore, blood can be classified as oxygenated or deoxygenated
do RBCs have organelles or nuclei?
NO
the lack of these structures maximizes the available volume for hemoglobin
what allows RBCs to bind with oxygen?
high concentrations of Hb within RBCs
what’s the diameter of a RBC?
7.8 μm
RBCs are in all tissues and tumors so you can use them like a ruler to see how big stuff is
why is the RBC a biconcave structure?
biconcave shape gives the RBC a relative excess of membrane, which affords the cell extraordinary flexibility and allows it to pass through openings much smaller in diameter than itself
in what diseases is the biconcave structure of RBCs effected?
sickle cell disease
hereditary spherocytosis
how does sickle cell decrease the flexibility of the structure of RBCs?
hemoglobin S forms a stiff rod inside the RBC and gives the cell a crescent or “sickle” shape
Sickle-shaped RBCs are not flexible and can accumulate in small blood vessels, blocking the flow of blood
Downstream tissues are deprived of oxygen, leading to a pain crisis
how does hereditary spherocytosis decrease the flexibility of the structure of RBCs?
results from molecular defects in genes that code for RBC membrane proteins or anchoring proteins
mutations in these proteins cause RBCs to have a spherical shape, leading to cytoskeletal instabilities and frequent hemolysis
a shortage of RBCs due to hemolysis leads to hemolytic anemia
what play an important role in maintaining the biconcave shape of RBCs?
plasma membrane proteins!
both integral membrane proteins and peripheral membrane proteins in the lipid bilayer of the plasma membrane of RBCs come together to form a lattice-like network that is anchored to the inner surface of the RBC plasma membrane
which plasma membrane proteins play an important role in maintaining the biconcave shape of RBCs?
- spectrin (most abundant)
- actin
- ankyrin
4, band 3 - band 4.1
- band 4.2
what does the cytoskeletal lattice of a RBC do?
the cytoskeletal lattice gives stability and flexibility to the RBCs
as RBCs make their way through vessels of different areas of the body, the chemical and physical environment changes
these changes prompt the membrane proteins to rearrange, and in turn the cell gains much flexibility
which plasma membrane proteins anchor the cytoskeletal lattice of the RBC to the cell membrane?
ankryin, band 3, band 4.1, and band 4.2
what is the structure of hemoglobin?
complex molecule containing four heme groups and four globin chains
what is a heme group made of?
each Hb molecule has 4 heme groups
each heme group consists of a protoporphyrin ring with an iron molecule at its center, attached by four nitrogen bonds
the iron molecule reversibly binds oxygen and carbon dioxide, allowing hemoglobin to carry oxygen to tissues and return carbon dioxide to the lungs
each heme group is surrounded by a globular polypeptide molecule called a globin chain
what are the types of globin chains in Hb?
Each heme group is surrounded by a globular polypeptide molecule called a globin chain
There are four types of globin chains – α, β, δ, and γ – and they always appear in pairs: two of one type of chain, and two of another
which globin chain is always in Hb?
hemoglobin always has one pair of α chains, but the other pair varies with age
what is adult hemoglobin?
hemoglobin A1
two alpha chains and two beta chains - each with their own heme molecule
what is fetal hemoglobin?
hemoglobin F
two α chains and two γ chains
is HbF or HbA better at binding oxygen?
hemoglobin F is much better at binding oxygen than hemoglobin A1, so that the fetus can extract oxygen from the mother’s bloodstream
when does the switch from HbF to HbA happen?
around 6 months
at 4 months the infant begins to make β chains, and the production of γ chains begins to diminish
swap is basically complete around 8 months of age
does γ chain production stop after 6 months old?
production of γ chains never entirely stops
a small amount (less than 1%) of total hemoglobin in the adult is composed of hemoglobin F
what is hemoglobin A2?
two α chains and two δ chains
it always comprises a small (1-2%) amount of total hemoglobin but its function is unknown.