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Haematology > Week 1- Normal erythrocytes (biochemistry) > Flashcards

Week 1- Normal erythrocytes (biochemistry) Flashcards

1
Q

What is the life span of RBCs?

A

120 days

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2
Q

Where are red blood cells destroyed?

A

The spleen removes fragile old RBCs from the circulation.

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3
Q

Describe the structure of RBC’s?

A

They are packed with haemoglobin
They have no nucleus or mitochondria
They have no DNA/RNA so no cell replication.

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4
Q

What is the process of producing RBC’s called?

A

Erythropoiesis

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5
Q

Where are red blood cells produced?

A

Bone marrow.

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6
Q

What do red blood cells arise from?

A

Pluripotent stem cells.

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7
Q

What happens to old red blood cells?

A

The spleen and liver engulf old red blood cells.

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8
Q

What occurs to the globular proteins from RBC’s when they are broken down?

A

They are broken down into amino acids which enter the blood stream.

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9
Q

What occurs to the haem group in RBC’s when they are broken down?

A

The haem group (minus iron) is converted to bilirubin. Bilirubin is transported to the liver and secreted into bile. The bilirubin breakdown products colour urine and faeces.

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10
Q

What happens to the iron in RBCs when they are broken down?

A

Iron binds to transferrin in the blood and is recycled.

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11
Q

What hormone regulates erythrocyte production?

A

Erythropoetin (EPO)

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12
Q

What organ releases EPO?

A

The kidney

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13
Q

Describe how hypoxia affects EPO release and red cell production?

A

Hypoxia is detected by the kidney causing it to release EPO hormone into the circulation. EPO acts on bone marrow to increase red cell production (erythropoiesis). This increases the oxygen carrying capacity in the blood and counteracts hypoxia.

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14
Q

Describe how normal oxygen levels/too much oxygen will affect EPO release?

A

Kidneys will sense that oxygen saturations are normal and EPO levels will drop.

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15
Q

Describe the progression of erythropoiesis?

A

Myeloid stem cells
Proerythroblast
Polychromatic erythroblast (Hb appears in cytoplasm)
Orthochromatic erythroblast (nucleus shrinks, full Hb present)
Erythroblast gets rid of its nucleus
Reticulocyte into circulation
Mature erythrocyte

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16
Q

What is the difference between a reticulocyte and an erythrocyte?

A

A reticulocyte is an immature red blood cell, it still has some RNA. An erythrocyte is a mature red blood cell (no DNA or RNA).

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17
Q

Why are red blood cells shaped the way they are? Also what is this shape called?

A

Biconcave shape- allows maximum gas diffusion by increasing the surface area to volume ratio. It also has a flexible membrane to allow it to squeeze through capillaries.

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18
Q

What is haematocrit?

A

The volume of red blood cells as a percentage of total blood volume. (40-50% in males and 36-46% in females).

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19
Q

What percentage do red blood cells, plasma, platelets and white blood cells make up of blood?

A

Plasma- 55%
Red blood cells- (40-50% in males, 36-46% in females)
White blood cells and platelets <1%.

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20
Q

What makes up the Buffy coat when blood is separated into its constituents?

A

White blood cells and platelets.

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21
Q

What regulates the RBC’s ion balance and cell volume?

A

Na+/K+ ATP ases (sodium pottasium pump)

THIS IS ENERGY DEPENDENT.

22
Q

If RBC’s don’t have mitochondria, how do they generate energy for the Na+/K+ ATPase’s?

A

They have to do anaerobic glycolysis

23
Q

To perform anaerobic glycolysis, what is the starting point?

A

Glucose is needed to start the reaction.

24
Q

In what state does oxygen bind iron?

A

Fe2+ state (Fe3+ cannot bind oxygen).

25
Q

How can you keep iron in its reduced state to help bind oxygen to the haemoglobin?

A

Need a reducing agent, something that will give up its electron to change Fe3+ to Fe2+. This is NAPH.

26
Q

What other pathway is some glucose metabolised by? What does this produce and what is its role?

A

Hexose monophosphate shunt.

It produces NADPH which is required to keep adequate levels of reduced glutathione

27
Q

What is produced when there are low partial pressures of oxygen and what is its role?

A

2,3 bisphosphoglycerate (BPG) is produced. It allows oxygen to be released from haemoglobin.

28
Q

Describe briefly the process of glycolysis. Include starting point, end point, byproducts and yield.

A

Process of converting glucose to pyruvate. It uses two ATP but gains 4 ATP so a net yield of 2 ATP.
Important biproducts are 2,3 BPG. This can be increased in times of high oxygen demand e.g. altitude, anaemia.
Another important byproduct is NADPH.

29
Q

What is glutathione?

A

Its an antioxidant that prevents oxygen free radicals from damaging the cells.

30
Q

In what state does glutathione help prevent against oxidative stress?

A

In its reduced state.

31
Q

What is a free radical?

A

Highly reactive molecule with one or more unpaired electron.

32
Q

What can excessive free radicals or no antioxidant protection cause for the cell?

A

Leads to damage of cellular structures and enzymes.

33
Q

Give examples of free radicals that threaten RBC’s?

A

Hydrogen peroxide

Superoxide (O2-)

34
Q

Describe how reduced glutathione can impact on hydrogen peroxide?

A

It detoxifies hydrogen peroxide to water.

35
Q

Which molecule is responsible for reducing glutathione?

A

NADPH

36
Q

What are the consequences of having a glucose-6- dehydrogenase deficiency?

A

This is the enzyme in the hexose monophosphate pathway (the pathway responsible for making NADPH). This means that glutathione can not be reduced meaning it is ineffective in protecting against oxygen free radicals.

37
Q

Which enzyme needs to be present for hydrogen peroxide to be converted to water by reduced glutathione?

A

Glutathione peroxidase

38
Q

Which enzyme needs to be present in converting oxidised glutathione to reduced glutathione by NADPH?

A

Glutathione reductase.

39
Q

How is CO2 produced by the tissues carried to the lungs?

A

10%- dissolved in solution
30%- bound to haemoglobin (carbamino-haemoglobin)
60%- as bicarbonate ions

40
Q

Which enzyme facilitates carbon dioxide being changed to bicarbonate ions?

A

Carbonic anhydrase.

41
Q

What is the equation when Co2 enters the RBC producing bicarbonate?

A

CO2 + H2O - H2CO3- H+ + HCO3-

42
Q

What occurs to the bicarbonate once it is produced in the red blood cell?

A

A chloride to bicarbonate exchange occurs. Chloride enters the cell and it swells, bicarbonate is removed from the cell.

43
Q

What occurs to the H+ produced along with bicarbonate ions in the RBC?

A

It is buffered with deoxygenated Hb.

44
Q

At the lungs, how does it differ in relation to bicarbonate ions?

A

Exchange is reversed, Cl- moves out of the cell and HCO3- is brought in. The reaction is driven backwards producing water and carbon dioxide, and the carbon dioxide is blown off in the lungs.

45
Q

What makes up adult haemoglobin?

A

4 subunits- 2 alpha, 2 beta.

4 haem groups containing iron surrounded by a porphyrin ring

46
Q

How many oxygen can one haem group bind?

A

1 oxygen.

47
Q

What does haemoglobin synthesis require?

A

Synthesis of globin molecules (alpha and beta chains)
Synthesis of a porphyrin ring
Iron

48
Q

How does the structure of fetal haemoglobin differ from adult haemoglobin?

A

It has two alpha chains and two gamma chains. In late gestation, gamma expression falls and beta expression rises.

49
Q

What is meant by allosteric interaction of oxygen and haemoglobin?

A

When one oxygen binds, it changes the shape of the haemoglobin affecting the ability of more oxygen to bind.

50
Q

At high concentrations of oxygen, describe the saturations of haemoglobin?

A

Haemoglobin is well saturated. If the oxygen concentration drops a little, it will still be fully saturated.

51
Q

At low concentrations of oxygen, describe the saturations of haemoglobin?

A

Oxygen dissociated from haemoglobin to tissues, steep drop in the sigmoidal curve.

52
Q

How does the affinity for oxygen of fetal haemoglobin differ from adults?

A

It has a higher affinity for oxygen meaning at lower partial pressures of oxygen, it will still be fully saturated. It can also take oxygen from the mothers haemoglobin.

Haematology (26 decks)

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