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Haematology > RBC- structure + function > Flashcards

RBC- structure + function Flashcards

1
Q

shape of RBC?

A

biconcave disc

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2
Q

explain the unique structure of RBC

A

-Biconcave shape
-Full of Hb
-No nucleus
-No mitochondria
-High surface area/volume
-Flexible

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3
Q

Risk of RBC being full of haemoglobin?

A

-high oncotic pressure, oxygen rich environment
-This is an oxidation risk

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4
Q

Pros and Cons of RBC having no nucleus

A

Pros:
-makes it more deformable to squeeze through capillaries
-allows more room for Hb

Cons:
-Cant divide
-cant replace damaged proteins
-this means it has a limited life span (120 days)

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5
Q

Consequences of RBC not having a mitochondria?

A

-Kreb’s cycle occurs in mitochondria
-due to not having a mitochondria it is limited to glycolysis which doesn’t produce a lot of energy for energy generation

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6
Q

pros and cons of RBC having a high surface area/volume?

A

Pros:
-allows for gas exchange

Cons:
-need to keep water out that could get in

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7
Q

Pros and cons of RBC being flexible?

A

Pros:
-Flexible to squeeze through capillaries

Cons:
-Specialised membrane made out of proteins required that can go wrong (proteins should mutate and shorten life span of RBC)

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8
Q

what makes the RBC membrane flexible?

A

it is not just a lipid bilayer

-it is flexible due to protein ‘spars’ and protein anchors

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9
Q

RBC have a high surface area/ volume to allow gas exchange, a problem with this is they need to keep water out
-what do RBC do to keep water out?

A

-Red cells use sodium potassium pump to maintain ion balance in the cell and keep water out
(But this needs ATP)

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10
Q

where are RBC produced?

A

bone marrow

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11
Q

RBC are produced in the _____ as a result of proliferation and differentation of ______

A

RBC are produced in the bone marrow as a result of proliferation and differentation of Haematopoietic Stem Cells (HSCs)

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12
Q

what regulates red cell production?

A

Erythropoiten

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13
Q

explain how erythropoiten and the kidneys work to regulate red cell production

A

Hypoxia sensed by kidneys > erythropoietin produced > erythropoietin stimulates red cell proliferation

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14
Q

average life span RBC?

A

120 days

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15
Q

where are RBCs destoyed?

A

normally in the spleen
-(and liver)

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16
Q

explain red cell destruction

A

Average life span 120 days
Normally occurs in spleen (and liver)

-Aged red cells are taken up by macrophages i.e. taken into circulation
-Red cell contents are recycled
-Globin chains recycled to amino acids
-Heme group broken down to iron and bilirubin
-Bilirubin taken to liver and conjugated
and then excreted in bile (colour faeces and urine)

17
Q

when a red blood cell is destroyed- what are globin chains recycled into?

A

Amino acids

18
Q

when RBC gets destroyed, what does the haem group get broken into?

A

Iron and bilirubin
-bilirubin is then taken to liver and conjugated and then excreted in bile (colour faeces and urine)

19
Q

what type of Fe ion can transport O2?

A

Fe2+ transports O2

(when Fe2+ gets oxidised into Fe3+ it can no longer transport O2)

20
Q

what does glycolysis give the RBC?

A

Glycolysis allows the RBC to get ATP

it also stops the Fe2+ from oxidising into Fe3+ as
- NADH acts as an electron donor stopping oxidation of Fe 2+ to Fe 3+ and generating NADH+ in the process

21
Q

explain how NADH prevents oxidation of Fe2+ into Fe3+

A

NADH acts as an electron donor stopping oxidation of Fe 2+ to Fe 3+ and generating NADH+ in the process

22
Q

what is metHb?

A

Hb with Fe3+ (this doesnt carry O2)

23
Q

what are reactive oxygen species?

A

-Are free radicals and have unpaired electrons
-Capable of interacting with other molecules (proteins, DNA) damaging their structures
E.g. superoxide + hydrogen peroxide

24
Q

role of Glutathione (GSH)?

A

Protects us from hydrogen peroxide by reacting with it to form water and an oxidised glutathione product (GSSG)

25
Q

how is GSH (glutathione) replenished?

A

GSH can be replenished by NADPH which in turn is generated by hexose monophosphate shunt

26
Q

what is the rate limiting enzyme in the reaction between hydrogen peroxide + GSH to form GSSG + water?

A

Glucose- 6- phosphate dehydrogenase (G6PD)

27
Q

CO2 transport:
-what % CO2 is dissolved, bound to Hb and in bicarbonate?

A

10% dissolved in solution
30% bound directly to Hb as carbamino-Hb
60% gets there as bicarbonate and the red cell has an important role in generating that bicarbonate

28
Q

shape of the Oxygen dissociation Curve and why?

A

Dissociation cure for Hb is sigmoidal (does not follow the michaelic menten kinetics)

Due to Allosteric affect- first oxygen binds to a haem in one subunit the Hb changes shape and makes it easier for the rest to bind (Cooperative binding)

29
Q

Explain how Foetal Hb (alpha2gamma2) has a different dissociation curve to adult Hb (alpha2beta2)

A

Foetal HB (alpha2gamma2)
-are saturated more at same pO2 as HbA so takes O2 from maternal circulation

30
Q

Explain hoe Myoglobin (in muscles) has a different dissociation curve to adult Hb

A

Myoglobin (in muscles)
- takes O2 from red cells and has different kinetics

31
Q

what would shift the O2 dissociation curve to the right (meaning it would release more O2 into tissue)?

A

-decrease in pH
-increase in 2,3 DPG (AKA 2,3, BPG)
-increase in temp

32
Q

what condition may increase 2,3 DPG?

A

chronic anaemia

33
Q

explain the shape of Hb

A

a tetrameric globular protein

34
Q

most common Hb in adults and structure?

A

HbA (97% adults)
2x alpha and 2x beta chains

35
Q

explain structure of HbA2 and how common

A

HbA2 (2.5%)
2x alpha and 2x delta chains

36
Q

explain structure of Hbf and who it is seen in

A

Hbf (fetal)
-usually seen in fetus
-seen in <1% adults)
2x alpha and 2x gamma

37
Q

structure of the heme group in haemoglobing?

A

heme group is Fe2+ in a flat porphyrin ring
-one heme per subgroup
-One oxygen molecule binds to one Fe2+ so there are 4 x O2 molecules per Hb as it is tetrameric

38
Q

function of Hb?

A

-deliver oxygen to the tissue
-act as a buffer for H+
-CO2 transport

Haematology (23 decks)

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