The Role of Red Blood Cells

sickle cell disease

Genetic disorder in which red blood cells have abnormal globin chain synthesis and take on an abnormal shape (crescent shape).

Biconcave disc

Increase the surface area to increase gas exchange Allows it to be flexible and deformable to allow movement through small blood vessels

Haem

Made in erythrocytes Iron bound to poryphyrin ring (give cells red colour) O2 binds to Iron in haem ring Haem rings bind to globin chains to form haemoglobin

Why do RBC need energy?

Maintain glycolysis (Provides ongoing energy for cell functions) Maintain iron in Hb in reduced (Fe2+) state (State which it can bind O2) Protect metabolic enzymes, Hb and membrane proteins from damage (To avoid premature cell damage/aging and clearance from the circulation) Preserve membrane structure (To maintain optimum cell function)

Decrease RBC production

anaemia (decrease Hb carriage and decrease in oxygen transport)

decreased erythropoietin

anaemia (low Hb) occurs during kidney failure

RBC metabolism

anaerobically 1. glycolysis 2. pentose phospahte pathway

RBC structure

bioconcave discs, no nucleus or other organelles, no cell division, bag of 270million haemoglobin molecules

RBC production - development

can take up to 3 weeks

increased erythropoietin

erythroycytosis (high Hb) occurs at high altitudes

Function of white blood cells

fight infections (<1% blood)

Lipid bilayer

gives cell membranes a flexible structure that forms a strong barrier between the cell and its surroundings Hydrophobic tails and hydrophilic heads

Decrease in RBC function

increase RBC destruction/clearance decrease in oxygen transport if the speed of RBC production cannot match rate of destruction

megaloblastic histology

increased RBC cell size, oval shape suggesting vitamin B12 or folate deficiency

Thalassemia

inherited defect in ability to produce globin chains, leading to anaemia

Function of platelets

key in coagulation (blood clotting) (<1% blood)

haemolysis

leads to anaemia and jaundice

iron deficiency histology

smaller, paler RBC

Anaemia symptoms

tiredness, weakness, pale skin, irregular heartbeat, shortness of breath, chest pain, dizziness, cold hands and feet, headaches

RBC function

transport O2 to tissues and CO2 to lungs (using haemoglobin)

cooperative binding

upon binding of first oxygen molecule, haemoglobin changes shape to allow easier binding of other O2 molecules

What can decrease RBC oxygen delivery to tissues?

- Increase carbon monoxide (CO) (Has higher affinity for Hb (binds more tightly to Hb ) than O2 so less Hb available for O2 carriage - Increase HbF (fetal haemoglobin) (Has higher affinity for O2 than Hb A (adult haemoglobin) so requires higher partial pressures of O2 for HbF to release O2 to tissues) - increase pH (alkalosis) - decrease temperature - decrease 2,3 DPG

What components make up blood?

- RBC - WBC - Platelets - Plasma

What can increase RBC oxygen delivery to tissues?

- decrease pH (acidosis) (Deoxyhaemoglobin binds to H+ ions more easily than oxyhaemoglobin) - increase carbon dioxide (CO2) (Contributes to acidosis) - increase temperature - increase 2,3 DPG (Preferentially binds to beta chains and displaces O2)

What influences RBC production? (4)

- erythropoietin - iron availibity and metabolism - vitamin B12 and folate - globin chains

Red blood cell production location

- when first born all bones in the body can make RBCs

Erthropoietin

- Glycoprotein hormone - Increases red cell production in bone marrow and release into blood stream in response to anaemia or hypoxaemia - Protects red cell precursors from apoptosis - > 90% produced in kidney; < 10% produced in liver

Red blood cells

(≈ 45% of blood) 20- 30 trillion RBC >80% of body's cells are RBC

Functions of plasma

(≈ 55% of blood) Maintains blood volume Role in coagulation (blood clotting) Transports hormones, nutrients and proteins

RBC lifespan

120 days

Globin chains in adults

2 alpha globin chains (chromosome 16) and 2 beta globin chains (chromosome 11)

How many oxygen molecules can haemoglobin bine?

4 O2 molecules per Hb molecules

Why does the body need O2?

Aerobic respiration Respiration = intracellular generation of usable energy to fuel processes in cells Adenosine triphosphate (ATP) is energy "currency" of cell More efficient than anaerobic respiration