RBCs And Haemoglobin (haematology, Physiology)

Question 1

What is the main function of RBCs

Answer 1

They carry oxygen from the lungs to systemic tissue and carbon dioxide to the lungs.

Question 2

Explain how RBCs transport carbon dioxide to lungs (8)

Answer 2

•Co2 diffuses from the peripheral tissues into the systemic capillaries.
•Only 7% of CO2 remains in plasma.
•About 25% of the CO2 binds to haemoglobin to form carbaminohaemoglobin.
•70% of the CO2 react with water to form CA which dissociate to form bicarbonate and hydrogen ions, the hydrogen ions are buffered by haemoglobin.
•The bicarbonate moves out of the RBCs in exchange for Chloride ions.
•In the lungs, dissolved CO2 diffuses out of the plasma into the alveoli.
•By the law of mass action, CO2 unbinds from haemoglobin and moves out of the RBCs.
•The CA reaction reverses, pulls bicarbonate into the RBCs and convert it back to CO2.

Question 3

Which enzyme catalyses the reaction btwn water and CO2?

Answer 3

Carbonic anhydrase enzyme

Question 4

Why do RBCs lack mitochondria?

Answer 4

Because RBCs carry oxygen, and cellular respiration in the mitochondria utilises oxygen. So if there is mitochondria in the RBCs the process will utilise the oxygen and decrease the oxygen supplied to tissues.

Question 5

By which process do RBCs generate ATP?

Answer 5

Glycolysis

Question 6

What are the normal haematocrit values?

Answer 6

Males- 46%
Females- 42%

Question 7

What happens when an erythrocyte is placed in:
1. A hypertonic medium
2. A hypotonic medium

Answer 7

1. It shrinks, but the rigid cytoskeleton remains and form a spiky surface, we now refer to it as a crenatus.
2. It swells and lose its biconcave disc shape.

Question 8

In which case does the RBC change its shape?

Answer 8

In a sickle cell disease

Question 9

During the metabolism of RBCs which molecule is produced by the reactions associated with glycolysis?

Answer 9

2,3-bisphosphoglycerate

Question 10

What do we call the protein found in RBCs?

Answer 10

Haemoglobin

Question 11

Normal values for haemoglobin levels

Answer 11

Males: 14-18 g/dL
Females: 12-16 g/dL

Question 12

What forms when haemoglobin binds to:
1. Carbon dioxide
2. Oxygen
3. Carbon monoxide

Answer 12

1. Carbaminohaemoglobin
2. Oxyhaemoglobin
3. Carboxyhaemoglobin

Question 13

What do we call the molecule that forms when haemoglobin has Fe3+?

Answer 13

Methemoglobin

Question 14

Explain the process of formation and metabolism of hemaglobin (6)

Answer 14

-Fe is ingested in diet.
-Fe is absorbed in the small intestines by active transport.
-Fe is transported by transferrin to the bone marrow where is binds to globin and forms haemoglobin.
-Haemoglobin in RBCs in metabolised in the spleen and it forms bilirubin.
-Bilirubin and other metabolites can be excreted in kidney through urine or in large intestines through faeces.
-Liver metabolises bilirubin and excretes it in the bile.
-Excess iron is stored in the liver as ferritin.

Question 15

Three stages of erythropoiesis in foetal life

Answer 15

Mesoblastic stage
Hepatic stage
Myeloid stage

Question 16

Factors necessary for erythropoiesis

Answer 16

•General factors such as erythropoietin, thyroxine, vitamins and haematopoietic growth factors.
•Factors necessary for the production of haemoglobin such as iron.
•Maturation factors such as vit b12, folic acid and intrinsic factor of castle.

Question 17

Lack of vit b12 during erythropoiesis causes what?

Answer 17

Pernicious anaemia

Question 18

How is haemoglobin recycled?

Answer 18

-Macrophages in the liver, spleen and bone marrow engulf RBCs.
-The Hb molecules are removed from hemolyzed (ruptured) RBCs.
-The Hb is broken into components.
- Only the iron of each heme unit is recycled.

Question 19

What is hemogluburia and what can cause it?

Answer 19

Excess haemoglobin in urine, can be caused by abnormally high hemolysis in bloodstream.

Question 20

What is hematuria and what causes it?

Answer 20

Whole RBCs in urine and it is caused by kidney or blood vessel damage.

Question 21

How is iron metabolized and excreted? (3)

Answer 21

Iron is removed from each heme unit forming green biliverdin.
Biliverdin get converted to orange-yellow bilirubin.
Bilirubin is excreted by the liver in bile.

Question 22

What does excess bilirubin cause?

Answer 22

It causes jaundice.

Question 23

What are the physiological causes of elevated RBC levels? (6)

Answer 23

-Age and gender
-After meals
-Higher altitude
-Emotional conditions
-Increased environmental temperature.
-Muscular exercise

Question 24

What are the physiology causes of low levels of RBCs? (3)

Answer 24

-Increased barometric pressure
-During sleep
-Pregnancy

Question 25

Pathological causes of variations in RBC number(4)

Answer 25

Primary polycythaemia: Polycythaemia vera

Secondary pathologies
-Chemical poisoning
-Congenital heart disease
-Emphysema

Question 26

What do we call RBCs that have:
1. Small size
2.Large size
3. No uniform size

Answer 26

1. Microcytes
2. Macrocytes
3. Anisocytes

Question 27

What causes the formation of:
1. Microcytes
2. Macrocytes
3. Anisocytes

Answer 27

1. Iron deficiency anaemia
2. Megaloblastic anaemia
3. Pernicious anemia

Question 28

What are the variations in the shape of RBCs? (5)

Answer 28

Spherocytosis
Poikilocytosis
Ellipticytosis
Crenation
Sickle cell

Question 29

What are the variations in RBC structure, explain.

Answer 29

Punctuate basophilism- Dots of basophilic materials.
Ring- Rings of basophilic material in the periphery of cell.
Howell-Jolly bodies- Nuclear fragments in the ectoplasm.

Question 30

Disorder caused by reduced hematocrit or haemoglobin?

Answer 30

Anaemia

Question 31

Three classifications of anaemia according to what causes it.

Answer 31

Hemorrhagic anaemia- caused by acute or chronic loss of blood.
Haemolytic anaemia- premature rupture of RBCs.
Aplastic anaemia- Destruction or inhibition of red bone marrow.

Question 32

What causes:
1. Iron-deficiency anaemia
2. Pernicious anaemia

Answer 32

1. Usually blood loss which causes reduced levels of iron in the body.
2. Vit B12 deficiency secondary to intrinsic factor deficiency.

Question 33

What causes abnormal haemoglobin?

Answer 33

Thalassaemia and sickle cell anaemia