Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecular Biology > Erythrocytes: Creation, Function and Destruction > Flashcards

Erythrocytes: Creation, Function and Destruction Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Describe the breakdown of the blood volume.

A
  • 70kg adult = ~5L blood volume.
    • 40% cells
    • 60% plasma
  • This is expressed as ‘packed cell volume’ or ‘haematocrit’ - typically 0.4 or 40%.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the ratio of red blood cells to white blood cells.

A
  • Red blood cells are 500x more numerous that white blood cells - approximately 2.4x1013.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the replacement rate of red blood cells? Why?

A

Red blood cells need to replace 1% per day to make up for the expected lifespan of 100-120 days.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the structure of red blood cells and relate this to function.

A
  • Red blood cells are subjected to high pressures and squeezed thorugh narrow capillaries every minute.
  • Biconcave disc
  • No nucleus
  • Pliable, high surface area / volume
  • Bag of Hb and enzymes for glycolysis
    • Unable to divide or make new proteins
  • Able to maintain membrane integrity and prevent oxidation
  • Main functions:
    • O2 and CO2 transport, acid/base balance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the formation of blood.

A
  • Embryological stem cells form blood islands in the yolk sac.
  • Cells migrate to the liver, then the spleen, then the bone marrow in the fetus.
  • At birth, marrow is widely distributed retreating to axial skeleton by adulthood.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the constituents of bone marrow stroma?

A
  • Fibroblasts
  • Macrophages
  • Endothelium
  • Fat cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the growth factors of bone marrow?

A
  • Interleukin 3
  • Erythropoietin (EPO- RBCs)
  • Androgens
  • Thyroxine
  • Growth hormone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is reticulin?

A

Remnants of mRNA left once the nucleus of a maturing RBC has been extruded. It is removed by the spleen in 1-2 days.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When and why would it be useful to measure reticulocytes?

A
  • It is a useful measure of marrow response to anaemia or treatment (eg. 5-10 fold rise).
  • Stained by new methylene blue on slide or on automated count.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How much iron should an adult have?

Where is this iron in the body?

A
  • Adults have 3000-5000mg of iron
  • 2/3 is in Hb
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is iron content in the body maintained?

A
  • Daily diet contains 10-20mg of which 1-2mg are absorbed in ferrous form - higher need in pregnancy / blood loss.
  • Fe2+ transported into duodenal enterocytes (small intestine absorptive cells).
  • Hepcidin regulates iron absorption and release from macrophages:
    • Increase in inflammatory disease = less available iron.
  • Body has no mechanism to excrete iron.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is iron lost?

A
  • Menstrual loss
  • Minor trauma
  • Gi - ~1ml blood per day
  • Blood sampling
  • Very small amounts in urine / skin shedding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is iron transported?

A
  • Transferrin is responsible for the transport and recycling of iron.
  • Transferrin receptors are increased in iron defficiency.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is ferritin?

A

Insoluble form of iron storage. This is a good measure of the body’s iron stores.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the body’s folic acid / folate need.

A
  • Daily requirement 0.1mg
    • ~0.25mg in diet - green veg and fruit
  • Absorbed in upper small intestine
  • Liver stores 10-20mg ie. only 100-200 days
  • Deficiency can be due to:
    • Poor intake
    • Absorption
    • Increased need
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the body’s B12 / cobalamin need.

A
  • Daily requirement = 1µg.
  • Diet may contain 5µg but all in animal derived products.
  • Gastric parietal cells produce ‘intrinsic factor’ - binds B12.
    • Atrophic gastritis - cannot produce intrinsic factor so B12 cannot be absorbed even if dietary intake is sufficient.
  • B12 absorbed in terminal ileum.
  • Transported on transcobalamin II via portal circulation to the liver.
  • Dietary defecit in vegans or pernicious anaemia - antibodies to intrinsic factor associated with gastric atrophy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are B12 and folate (folic acid) required for?

A
  • Both are required in RBC production.
  • B12 is required in change from 5-methyl tetrahydrofolate (THF) to THF.
18
Q

Describe the properties of erythropoietin.

A
  • Glycosylated 165 amino acid protein.
  • Production:
    • 90% renal
    • 10% liver
  • No body stores, so switched on by:
    • Tissue hypoxia or anaemia
    • High altitude
    • EPO producing tumours eg, renal
  • Drives erythropoiesis in the bone marrow.
  • Useful recombinant drug for renal anaemia (underproduction) and myelodysplasia (increased drive to erythropoiesis).
19
Q

What is the role of hypoxia inducible factor?

A

Senses O2 levels in peritubular cells.

20
Q

Describe the effect of low O2 on EPO production and vice versa.

A
  • At low O2 levels, mRNA for EPO is increased and EPO is produced.
  • So, the lower the tissue pO2, the higher the EPO production.
  • The higher the pO2, the lower the EPO production.
21
Q

What causes changes in the RBC membrane?

A

Inherited mutations can cause shape changes.

Eg. spherocytosis.

22
Q

What factor is responsible for the flexibility and resilience of RBCs?

A
  • Spectrin gives RBCs flexibility and resilience.
  • Abnormal production of spectrin causes odd shapes and forms rouge RBCs.
23
Q

How is O2 carried in the blood?

A

It binds to haem which is anchored to the globin chains of haemoglobin or myoglobin.

24
Q

Describe the structure of adult haemoglobin.

A
  • Haemoglobin needs:
    • 2 α chains (chromosome 16) zeta (early fetal) then alpha.
    • 2 β chains (chromosome 22) epsilon, then gamma, then delta, then beta.
  • It is a tetramer with 4 globin chains, each of which has a haem group attached.
25
Q

What causes thalassaemia?

A

An inherited defect in globin chain production

26
Q

What causes sickle cell disease?

A

One amino acid change in a Hb beta chain

27
Q

Show diagramatic representation of a sickle cell compared with a normal RBC.

What can this cause?

A
  • Sickle cells (abnormal haemoglobin) can cause blockage of vessels.
28
Q

Why can’t erythrocytes produce proteins for energy?

A

Becauase they have no nucleus

29
Q

What is the role of RBC enzymes?

A
  • RBCs cannot make proteins because they have no nucleus, but they do need enough enzymes to make energy.
  • RBC enzymes control the whole glycolytic pathway from glucose to lactate and pyruvate.
  • These provide energy for:
    • Maintaining membrane integrity
    • Preventing oxidation of enxymes and Fe2+
    • Maintaining gradients of K+ and Ca2+
30
Q

What is caused by RBC enzyme deficiencies (eg. pyruvate or G6DP deficiency)?

A

These deficiencies can cause anaemia by haemolysis - increased rate of RBC breakdown.

31
Q

What is the key function of RBCs?

A
  • Key function is to bind Hb to O2 at high O2 tension and release it at low O2 tension.
  • Basically delivery of oxygen and removal or carbon dioxide.
32
Q

What happens to the oxygen dissociation curve during acidosis or an increase in temperature?

A
  • Acidosis and increased temperature will cause right shift.
  • Hence, DELIVER MORE O2 TO THE TISSUES.
33
Q

What is the effect of 2,3DPG on the oxygen dissociation curve?

A
  • It produces a right shift of the O2 curve, hence more oxygen is released to the tissues.
  • 2,3 DPG enters the globin chains, releasing oxygen.
  • 2,3 DPG increased in exercise / anaemia / high altitude.
34
Q

What is myoglobin?

A
  • Store of oxygen in skeletal muscle for immediate use.
  • 1 haem group and 1 globin chain.
35
Q

What is the secondary function of erythrocytes?

A
  • Acid-base balance
    • Regulation of free H+ ions in body fluids
    • pH normally 7.35-7.45
    • pH is measured on log scale, so pH 7 is 10x greater H+ concentration as pH of 8.
36
Q

Why is acid-base balance important?

A
  • Enzymes work optimally at physiological pH.
  • Cell membranes become leaky in acidosis.
  • Neurones become less able to transmit in acidosis - they become hyperactive in alkalosis.
37
Q

Describe the buffer system: red cell bicarbonate.

A
  • Within the red cells, CO2 is produced from tissue all the time.
  • This passes out of the tissue and enters the red cells.
  • The reaction that happens within the red cells (diagram) is in constant equilibrium; increase in hydrogen ions will push the reaction to the left, this is catalysed by carbonic anhydrase.
  • The majority of CO2 carried in the blood is not carried as CO2, but rather as bicarbonate.
  • Bicarbonate ions leave the RBC and enter the plasma.
  • The hydrogen ions are either bound within RBCs, or leave the RBCs and are replaced by chloride ions.
38
Q

What happens to RBCs in the lungs?

A
  • Deoxygenated RBCs enter the lungs by passive diffusion and become oxygenated.
  • This process must happen very quickly to get the bicarbonate to turn back into CO2 which we then breathe out.
  • Red cells then passively absorb the O2.
39
Q

Describe the buffer system: haemoglobin.

A
  • H+ combines with Hb after loss of O2.
  • Low pH decreases hB affinity for O2.
  • CO2 + Hb ↔︎ HbCOO- + H+
40
Q

Describe the loss / destruction of RBCs.

A
  • As RBCs age:
    • Membrane becomes more rigid
    • Loss of glycolytic enzymes
    • Neoantigens exposed on the cell surface
  • Some RBCs are lost from:
    • GI tract
    • Into soft tissues
    • Menstrual loss
  • Some RBC destroyed within the body
41
Q

Describe RBC destruction in circulation and spleen/liver recycling.

A
  • Free Hb ‘mopped up’ by haptoglobin - cleared by the liver. Any excess can appear in the urine.
  • Globin chains broken up into amino acids.
  • Iron bound to transferrin and returned to macrophages.
  • Porphyrin ring becomes bilirubin-bound to albumin and ‘conjugated’ to glucuronide - excreted in bile.
42
Q
A

Molecular Biology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions