Red Blood Corpuscles

Question 1

Describe the structure of erythrocytes

Answer 1

No organelles (including nucleus) –> increased volume for hemoglobin
Shaped as biconcave discs
7.5 µm in diameter

Question 2

What is Mean Corpuscular Volume (MCV)?

Answer 2

MCV measures the average size of your red blood cells
MCV ≈ 90 μm3

Question 3

What is Mean Corpuscular Hemoglobin (MCH)?

Answer 3

Average amount of hemoglobin in each RBC
MCH ≈ 30 picograms

Question 4

What is Mean Corpuscular Hemoglobin Concentration (MCHC)?

Answer 4

Measure of the average concentration of hemoglobin inside a single RBC.
MCHC ≈ 33%

Question 5

Why are RBCs biconcave?

Answer 5

Increases its flexibility (allows it to fit into capillaries and gaps between endothelial cells in splenic sinusoids)
Increase SA for diffusion of gases

Question 6

What are RBC cytoskeletal membrane proteins?

Answer 6

Proteins forming a lattice network that is anchored to the inner surface of the RBC plasma membrane.

Question 7

What is the function of the RBC cytoskeletal proteins?

Answer 7

Allows RBCs to bend while passing through the circulation

Question 8

What proteins form the RBC cytoskeleton?

Answer 8

Spectrin (most abundant) and actin form the cytoskeleton
Ankyrin, band 3, band 4.1 and band 4.2 bind the cytoskeletal lattice to the plasma membrane

Question 9

What are some disorders caused by defects in cytoskeletal membrane proteins?

Answer 9

Hereditary Spherocytosis (HS)
Hereditary Elliptocytosis (HE)

HS is caused by mutations in RBC cytoskeletal proteins; it affects their spherical shape, leading to cytoskeletal instabilities and frequent hemolysis (which causes hemolytic anemia)

Question 10

What is Sickle Cell Disease (SCD)?

Answer 10

Hemoglobin S forms a rod inside the RBCs, making them form a sickle shape.
Because they are not flexible, they accumulate in small blood vessels, blocking the flow of blood causing oxygen deprivation and pain crises.

Question 11

What is the average RBC count per mm3?

Answer 11

Men: 4.7 – 6.1 million cells /mm3 or (µl)
Women: 4.2 – 5.4 million cells/mm3

Average number: 5 million/mm3

Question 12

What are the functions of RBCs?

Answer 12

1. Contain hemoglobin for transporting respiratory gases and acid-base buffering.
2. Contain carbonic anhydrase which catalyses the revesible reaction between CO2 and H2O to form H2CO3 which facilitates the transport of CO2.

Question 13

What are the types of chains which can form hemoglobin?

Answer 13

Alpha chains, Beta chains, Gamma chains, and Delta chains

Question 14

What is the composition of adult hemoglobin?

Answer 14

Adult hemoglobin (hemoglobin A1) is formed from two alpha and two beta chains

Question 15

What is the composition of fetal hemoglobin?

Answer 15

Fetal hemoglobin (hemoglobin F) is formed from two alpha and two gamma chains

Binds to oxygen better than A1 enabling oxygen extracting from the mother’s bloodstream

Question 16

When does hemoglobin switch from F to A1?

Answer 16

At around 4 months, gamma chain production begins diminishing.
Hemoglobin F switches to Hemoglobin A1 at around 6 months.
At 8 months, the switch is virtually complete

Production of gamma chains never ceases entirely, so ~1% of hemoglobin is hemoglobin F

Question 17

What is hemoglobin A2?

Answer 17

Hemoglobin A2 is formed from two alpha and two delta chains and forms ~1-2% of total hemoglobin

Question 18

Describe how the hemoglobin chains vary throughout life.

Answer 18

Question 19

How many oxygen molecules can one hemoglobin molecule bind to?

Answer 19

Each hemoglobin molecule can bind reversibly to four oxygen molecules

Question 20

What are the normal hemoglobin values?

Answer 20

Male: 13–18 gram/100 ml
Females: 12–16 gram/100 ml

Average: 15 gram/100 ml

Question 21

What are some RBC disorders?

Answer 21

Anemia: Decrease oxygen delivery to tissues causing anemia hypoxia
Polycythemia: Increase blood viscosity causing cause heart failure