Ch4

Question 1

Why is it important for complex organisms to have a circulatory system? What does it help?

Answer 1

• due to large body size, simple diffusion cannot effectively transport nutrients and oxygen to various tissues and remove metabolic wastes from them –> efficient transport system is required
• blood circulatory system helps to maintain a constant internal environment

Question 2

What is blood and what does it includes? What does blood cells include? What are platelets? What is Buffy coat? What is the name of the percentage representing the % of RBC in terms of whole blood?

Answer 2

• fluid tissue
• blood = plasma (55%) + blood cells and platelets (45%)
• red blood cells (erythrocytes) and white blood cells (leukocytes)
• blood cell fragments
• WBC and platelets
• haematocrit

Question 3

What is plasma and what is its characteristics? What is the composition of plasma?

Answer 3

• plasma = blood - blood cells
• slightly alkaline and yellowish fluid
• 90% water and 10% solutes

Question 4

What does plasma include? (roughly)

Answer 4

• protein
• nutrients
• metabolic wastes
• gases
• ions or electrolytes
• regulatory substances

Question 5

What kind of protein does plasma include?

Answer 5

• albumins (60%)
  => most abundant
  => synthesised by the liver
  => maintain the osmotic pressure and pH of blood
• globulins (36%)
  => include antibodies, clotting proteins, protein that bind lipid, fat-soluble hormones and metal ions
• fibrinogen (4%)
  => synthesised by the liver
  => important in blood clotting

Question 6

What kind of nutrients does plasma include? What is their result?

Answer 6

• glucose, amino acids, fatty acids, glycerol and vitamins
• transported to the cells and assimilated

Question 7

What kind of metabolic wastes does plasma include? What are the results of these wastes?

Answer 7

• CO2, urea, uric acid and creatinine
• transported to kidneys and removed

Question 8

What gases are present in plasma?

Answer 8

• O2 and CO2
• most O2 and little CO2 are bound to haemoglobin in RBC
• most CO2 is found in plasma as HCO3-

Question 9

What ions and electrolytes are present in plasma?

Answer 9

• cations: Na+, K+ and Ca2+ (for neuromuscular signalling)
• anions: Cl-, HCO3- and PO43- (for maintenance of plasma pH)

Question 10

Why do plasma contains regulatory substances?

Answer 10

• chemical messages or regulators are transported to the target organs where they perform their regulatory functions

Question 11

What are the characteristics and function of red blood cells (erythrocytes)? Write out the chemical equation of the reaction of CO2 and its respective enzyme.

Answer 11

• most abundant blood cells which are produced by haematopoietic stem cells in red bone marrow
• transport O2 and CO2 in the blood
• presence of haemoglobin for O2 transport and carbonic anhydrase for CO2 transport
• biconcave disc shape provides large surface area to volume ratio for gaseous exchange
• lack nuclei, mitochondria and other organelles in mature RBC to pack more haemoglobin
• CO2 + H2O ⇄ H2CO3 ⇄ H+ + HCO3-

Question 12

What is haemoglobin? What does it contain? What does Hb do to O2 and what is the chemical equation?

Answer 12

• most abundant protein in RBC
• has 2𝛼 and 2𝛽 chains, each covalently bound to an iron-containing heme group
• O2 combines with Hb in the lungs and is readily released in tissues
• Hb + 4O2 ⇄ HbO8

Question 13

What is the lifecycle of RBC? Why is it so short?

Answer 13

• have a lifespan of about 120 days
• cannot undergo cell division due to absence of nucleus
• old RBC are destroyed by spleen and liver as there are many macrophages
• new RBC are synthesised very quickly by erythropoiesis from hematopoietic stem cells in red bone marrow

Question 14

How is RBC produced? What does the development process need?

Answer 14

• low oxygen levels in blood stimulates the kidneys to release erythropoietin which activates the differentiation of hematopoietic stem cells into RBC in red bone marrow
• vitamin B12, folic acid and iron

Question 15

Who is responsible for the destruction of RBC? What will it be broken down to? What is the function of each product respectively?

Answer 15

• spleen is responsible for storing blood cells and destroying old RBC
• most RBC are engulfed by macrophages in the spleen and partly in the liver
• heme, iron and globin
• heme –> will become bilirubin and released into bloodstream –> act as the material of bile formation in the liver and is excreted in the faeces
• iron –> recycled for new RBC synthesis
• globin –> break down into amino acids by deamination

Question 16

What are the characteristics of WBC (leukocytes)? What the five major types?

Answer 16

• compared to RBC is far less numerous
• nucleated and possess all cellular machinery for protein synthesis
• can be found in tissues due to their ability to penetrate through pored in the capillaries
• (granulocytes) neutrophils, eosinophils, basophils
• (agranulocytes) monocytes and lymphocytes

Question 17

What are platelets? What is its characteristic? What is its function?

Answer 17

• cell fragments arising from breakdown of megakaryocytes in the bone marrow
• contain various organelles but have no nucleus
• plays an important role in hemostasis

Question 18

What are the process of hemostasis?

Answer 18

• vascular spasm
  => when a blood vessel is injured, platelets stimulate a vasoconstriction called vascular spasm –> increase resistance to blood flow –> lower blood loss
• formation of platelet plug
  => injury to lining of vessels exposes collagen fibres –> platelets adhere to the site of injury –> secretion of ADP –> platelets become sticky –> aggregation of platelets form a platelet plug –> limit blood loss
• formation of blood clot
  => requires fibrin –> forms a meshwork that traps blood cells and platelets which is the blood clot that seals the wound
  => requires a sequence of reactions known as coagulation cascade
  => plasma proteins called coagulation factors undergo a series of proteolytic activation
  => activated coagulation factors act as proteolytic enzymes for the next step

Question 19

What are the last 3 steps in blood coagulation?

Answer 19

• factor Xa –> conversion of prothrombin to thrombin in the presence of Ca2+
• thrombin –> conversion of soluble fibrinogen to insoluble fibrin
• factor XIIIa –> act as fibrin stabilising factor to form insoluble blood clot

Question 20

How are the coagulation factors synthesised? What is its characteristics? What is serum?

Answer 20

• most coagulation factors are synthesised by liver and are released into the plasma in their inactive form
• several coagulation factors (VIII and IX) are crucial for the formation of a blood clot
• plasma - coagulation factors

Question 21

What is haemophilia? What is its therapy?

Answer 21

• a genetic disease caused by the mutation of blood clotting factor genes –> excessive bleeding
• factor VIII and factor IX genes are located on X chromosome –> sex-linked
• hemophilia A (80%) –> factor VIII
• haemophilia B (20%) –> factor IX
• replacement therapy –> intravenous injection of factor VIII or IX

Question 22

What is the reason of vitamin K deficiency? What is the result of vitamin K deficiency?

Answer 22

• vitamin K is a fat-soluble vitamin which is important for blood clotting as it is for the maturation of several clotting factors including factor X and prothrombin
• absence of vitamin K will lead to defective blood clotting mechanism –> excessive bleeding