Fundamentals of Blood and Red Blood Cells Flashcards
Blood has a cellular and extracellular component.
True or False?d
True
What colour is blood plasma?
Yellow
What % of blood is water?
92%
What do inorganic salts do in blood plasma?
Buffer the pH and contribute in osmotic balance and the regulation of the cell membrane potential
diagram of blood components
Haematocrit
% of red blood cells relative to the total blood volume
Platelet purpose?
essential for blood clotting
Platelets are not really cells but
rather cytoplasmic cell fragments of cellular precursors
Red blood cells have a characteristic shape ——, which allows them to
- “flexible disc”, biconcave shape
- Allows them to travel in vessels and narrow capillaries
- Large surface for gas exchange
Normal haematocrit in men and women
- Men: 46%
- Women: 42%
RBC characteristics
- no nucleus
- reduced number of organelles and cellular membrane structures
- short life span: 120 days in circulation
Older RBCS rupture easily and the debris left is degraded by
macrophages
What % of RBC volume is taken up by haemoglobin?
25%
RBC plasma membrane composition
is asymetrical with mainly negatively charged phospholipids (those with a terminal primary amino group) being located on the inner part of the lipid bilayer
Why is RBC membrane composition important?
for cell signaling communication
Biconcave shape of RBC achieved by?
Via a mesh-like network of the protein spectrum
What is the primary component of RBC cytoskeleton that interacts with cell membrane proteins?
Spectrin
Shape of spectrin?
Filamentous shape
Spectrin gene abnormalities cause
spherical and fragile RBCs
What are platelets released by?
Megakaryocytes
What do platelets contain?
Enzymes that initiate blood clotting
Blood clotting
- when vessels are damaged circulating blood platelets come in contact with collagen fibers, causing the platelets to swell and form a “sticky patch”, which begins the blood clotting cascade
- Clotting relies on inactivated precursor proteins (prothrombin, fibrinogen) that are produced by the liver and circulate in the blood. These are cleaved to thrombin and fibrin respectively, leading to the formation of a blood clot prior to the formation of scar tissue in wound healing.
Automate blood counts
Erythropoiesis
- from birth, the bone marrow is the site of haematopoiesis in humans
- erythropoiesis takes place in the haematopoeitic/red marrows, which is located within trabecular (spongy) bone at the end of long bones
RBC production equation and include numbers
RBC volume/ RBC life span
2250ml/120 days = 18.75 ml/day average production in a healthy adult
Erythropoetin
Reticulocytes
- when haemoglobin synthesis has been completed the erythroblast nucleus, that has been progressively condensing, gets expelled yielding the reticulocyte
- reticulocytes enter vascular circulation and mature in 1-3 days to erythrocytes
Normal levels of reticulocytes in blood circulation?
25-125 x10^9/L
What does an elevated number of reticulocytes indicate?
Active bone marrow response to blood loss or anaemia (compensation)
What cell is this??
Blood films stained with Romanowsky (Giemsa) stain that have an increased number of reticulocytes appear to have a blue tinge. This called polychromasia.
The blue tinge is due to high levels of RNA. As the cells mature towards erythrocytes the RNA is replaced by increased amounts of haemoglobin and the cell colour changes to a pink/red one that’s is characteristic of red blood cells.
HbA/adult haemoglobin structure
- consist of four subunits; two identical alpha chains and two identical beta chains
- four haeme groups bound to each of the subunits
HbF/ fetal haemoglobin structure
- consists of four subunits; two identical alpha chains and two identical gamma chains
- four haeme groups bound to each of the subunits
Which has a stronger binding affinity to oxygen; HbA or HbF?
HbF
An example of secondary protein structure in haemoglobin?
Alpha helix chains
What is responsible for haemoglobins red colour>
Haeme groups
Haeme groups structure
- four pyrrole rings
- that make a tetrapyrrole ring called protoporphyrin
- each of the pyrrole rings contain nitrogen atoms that participate in the binding of Fe2+ to oxygen
Electron transfer when oxygen binds to haeme group
- partial transfer of an electron from Fe to P2 yielding Fe3+ and a superoxide (O2-; reactive oxygen species ROS)
What ensures ROS O2- is not released into tissues
haemogobin protein subunits
What is each pyrrole ring linked to next by?
methine bridge
double bond CH single bond (= CH – ).
Hb affinity for oxygen
- the sigmoid shape shows that O2 binding to one haeme group increases the possibility of O2 binding in the three other haeme groups
- the unloading of O2 from one haeme group assists the unloading of O2 from the other three haeme groups CO-operative
- this ensures that oxygen binds strongly to Hb in the lung, where paO2 is high and is easily released in tissues where paO2 is lower
HAve to watch to see whether she explains sequential and concerted?
O2 release from Hb tetramer
- 2,3-BPG/DPG is present in RBCs at similar concentration to haemoglobin
- lowers affinity of oxygen for haemoglobin, ensuring the release of oxygen in tissues
- 2,3-BPG is an allosteric regulator of haemoglobin, it binds to the center of the tetramer at a site different from oxygen binding ones
- causes haemoglobin conformation with lower oxygen binding affintiy, where more oxygen binding sites are occupied
- lower oxygen binding affinity ensures easier O2 release ,
An allosteric interaction between an enzyme and its substrate refers to the event
when the substrate binds to a site different from the enzyme’s active site, causing a conformational change for the enzyme and a change in substrate affinity and consequently a change in function
2,3 - BPG
2,3-Biphosphoglycerate is an anion
Hb affinity for O2 diagram
What is the % of nucleotide sequence similarity between beta chain of HbA and gamma chain for HbF?
72%
Why does 2,3-BPG not bind to HbF as efficiently as it binds to HbA?
Only 72% of nucleotide sequence similar between HbA beta chain and HbF gamma chain
Why doe fetal RBCs have higher affinity for O2 than maternal RBCs?
oxygen can be efficiently transferred from maternal RBCs to fetal RBCs
diagram from HbA vs HbF
The alpha, beta and gamma chains in haemoglobin are the result of
duplication events
second diagram from HbA vs HbF
Cellular respiration equation and how much ATP
C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP
Fermentation equation and how much ATP
C6H12O6 → 2C3H6O3 + 2 ATP
When and where does fermentation take place?Byproducts?
- takes place in muscle cells at times of intense exercise, when ATP is needed faster than oxygen can be transported and yields lactate (lactic acid)
- Lactate build up causes a lowering pH and muscle fatigue
oxygen transfer diagram
Myoglobin function
An additional route for oxygen in the muscle and works to create a reserve of O2 to be used when muscles are active
Myoglobin structure
- same structure as one haemoglobin subunit and contains on haeme group
Myoglobin is found where and ensures?
present in skeletal muscle
ensures oxygen diffusion in these cells
Is myglobin more effective in delivering oxygen to tissues than haemoglobin?
No
Haemoglobin can deliver 10x more oxygen to tissues compared to myglobin
myglobin slide diagram
CO2 equation in blood and include enzyme
Bohr affect
CO2 and H+ act as allosteric regulators of haemoglobn by altering its affinity for oxygen binding
CO2 transport slide
watch
CO2 reacts with the terminal amino groups of deoxyhaemoglobin and forms carbamate groups, HCO3- transport across the RBC plasma membrane is coupled with transport of CL- in the opposite direction.
Carbon Monoxide
- binds to haemoglobin at the oxygen binding site yielding carboxyhaemoglobin
- binds very tightly to haemoglobin, aprrox 200 times stronger than oxygen, which displaces bound oxygen
- CO binding to one out of the four haeme groups will increase haemoglobin affinity for oxygen as there is a no release in tissues
CO poisoning symptoms
- disorientation
- nausea
- lethargy
- weakness
How to treat CO?
hyperbaric oxygen therapy
Hypovolaemia
- loss of extra-cellular ffluid
- can be attributed to loss of blood volume
Causes of hypovalaemia (4):
- excess bleeding due to trauma
- diarrhea or vomiting
- renal failure
- use of diuretics
- last two are linked to renal system function
Symptoms of hypovolaemia
- fatigue
- headaches
- cyanosis
- tachycardia
- symptoms are consistent with more than 10% loss of blood volume
If hypovolaemia is left untreated can cause
hypovolaemic shock
organ failure
death
Anaemia
- reduced haemoglobin concentration, which leads to reduced oxygen transport
Anaemia Clinical Symptoms (4):
- tachycardia
- breathlessness
- pallor
- lethargy
Causes of Anaemia (7):
- iron deficiency
- bone marrow suppression; myledoysplastic syndrome, aplastic anaemia
- blood loss
- folate deficiency; B12 deficiency (pernicious anaemia)
- haemolysis
- inherited problems in haemoglobin synthesis beta thalasseaemia
- autoimmunity
Sickle Cell Anaemia
- caused by a single mutation, beta globin position 5 glutamate replace with valine
- production of HbS, oxyhaemoglobin is not affected but ddeoxyhaemoglobin becomes fibrous and forms aggregates
- RBCs in sickle cell anaemia have a characteristic sickle like shape, which clog capillaries and prohibit smooth blood flow
- RBCs stick frequently to vessels walls and remain in blood circulation for a reduced amount of time.
Alpha Thalassaemia is cased by
- Deletion/inactivation of three or four of the alpha globin genes
- Deletion/Inactivation of four genes: Hb Bart syndrome leads to embryonic lethality
- Deletion/Inactivation of three genes: HbH disease leads to enlarged spleen/liver, anaemia (may require blood transfusion)
Beta Thalassaemia
- caused by mutations or deletions of the beta globin gene:
Types of anaemia: Bone marrow malfunction:
- aplastic anaemia
- fanconi anaemia
- the anaemia forms part of the diagnosis of a wider and more complex problem
Polycythaemia
- characterised by elevated haematocrit
- example of a myeloproliferative neoplasm
Polycythaemia is often caused by:
- gene mutations that affect JAK-STAT signaling pathway
- malfunction of EPO and EPO receptor
Plycythaemia symptoms:
- fatigue
- dizziness
- headaches
- gum bleeding
- nose bleeding
- can affect heart function, spleen function, blood clotting
