PSC1002/L02 Blood

Question 1

What percentage of total body weight is blood?

Answer 1

8%

Question 2

Give 3 functions of blood.

Answer 2

Gas transport and exchange
Distributing solutes
Immune functions
Maintaining body temperature
Regulates blood clotting
Preserving acid-base homeostasis
Stabilising blood pressure

Question 3

What is blood composed of? (3)

Answer 3

Erythrocytes
Leukocytes
Thrombocytes

Question 4

How does blood separate when centrifuged? (3)

Answer 4

55% soluble materials (top)
1% buffy coat - white blood cells and platelets
44% haematocrit (bottom)

Question 5

What are the 2 main functions of plasma?

Answer 5

Thermoregulation
Transport

Question 6

How does a high percentage of water in plasma affect properties? (3)

Answer 6

High specific heat capacity
Heat not needed lost to environment
Precentage of water determines blood viscosity/ bp

Question 7

Describe serum albumins (3)

Answer 7

55% of plasma volume
Large protein synthesised in liver
Maintains osmotic pressure of plasma
Transport of lipids & steroid hormones

Question 8

Describe globulins (3).

Answer 8

38% of plasma volume
Transport ions, hormones, lipids
Immune proteins made by leukocytes

Question 9

Describe clotting proteins. (3)

Answer 9

7% plasma volume
Essential for blood clotting
Synthesised in liver

Question 10

What makes up the final 1% of blood plasma?

Answer 10

Regulatory proteins
Enzymes, proenzymes, hormones

Question 11

What does a normal electrophoretic pattern of plasma proteins show? (5)

Answer 11

Albumin, a1, a2, B and Y globulins

Question 12

Give 3 causes of cirrhosis.

Answer 12

Cancer
Alcoholism
Viral hepatitis

Question 13

What can cirrhosis lead to? (2)

Answer 13

Decrease in production of plasma proteins
Decreased colloidal osmotic pressure
Fluid loss to ECS
Severe edema in abdomen
Decline in clotting factor/easy bruising

Question 14

What is the volume of erythrocytes?

Answer 14

80-96 femtolitres

Question 15

Where are small/large RBCs found?

Answer 15

Small - macrocytic in iron deficiency anaemia
Large - microcytic in folate (vitamin B9)

Question 16

Where does erythropoiesis occur?

Answer 16

Bone marrow

Question 17

Describe the 7 steps in erythropoiesis.

Answer 17

Hematopoietic cell
Erythrocyte-CFU
Proerythroblast
Early erythroblast
Late erythroblast
Reticulocyte
Erythrocyte

Question 18

In which step of erythropoiesis does the hormone erythropoietin stop being produced?

Answer 18

3 - proerythroblast

Question 19

In which step of erythropoiesis is haemoglobin synthesised?

Answer 19

4 - early erythroblast

Question 20

In which step of erythropoiesis is the nucleus ejected?

Answer 20

5 - late erythroblast

Question 21

In which step of erythropoiesis are organelles ejected?

Answer 21

6 - reticulocyte

Question 22

How long after a bleed is homeostasis achieved in the blood?

Answer 22

26 days

Question 23

How are erythrocytes disposed of at the end of their life?

Answer 23

Phagocytosed in liver and spleen

Question 24

What are heme components recycled into? (2)

Answer 24

Heme into biliverdin then bilirubin, secreted in bile from liver
Iron stored by protein ferritin in liver

Question 25

Describe Glucose-6-phosphate dehydrogenase (G6PD).

Answer 25

Predisposes to red blood cell breakdown (haemolytic crisis) when exposed to certain environmental triggers

Question 26

Describe the 2 parts of a haemoglobin molecule.

Answer 26

Globin - 4 protein chains
4 iron containing haem groups

Question 27

Describe the structure of the Haem group.

Answer 27

Porphyrin ring containing 1 iron atom

Question 28

Describe the structure of iron with and without oxygen.

Answer 28

Without: Fe2+ (ferrous)
With: Fe3+ (ferric)

Question 29

Give the 4 forms of globin protein.

Answer 29

Alpha, beta, gamma, delta

Question 30

What are the 3 combinations of globin chains in adults?

Answer 30

HbA - 2A, 2B
HbA2 - 2A, 2D
HbF - 2A, 2Y

Question 31

What are the 2 forms of haemoglobin and where are they found?

Answer 31

r form - high O2 affinity e.g., in lungs
t form - low O2 affinity e.g., in peripheral tissues

Question 32

Give 3 other molecules that haemoglobin can bind.

Answer 32

Carbon dioxide
Acidic hydrogen portion of carbonic acid
Carbon monoxide
Nitric oxide

Question 33

What are haemoglobinopathies?

Answer 33

Abnormal haemoglobin chains

Question 34

What are thalassaemias?

Answer 34

Decreased amount of globin chains or absent globin chains due to gene expression defects

Question 35

Describe sickle cell anaemia. (3)

Answer 35

Mutation is B-globin gene
Glutamic acid replaced by valine
Creates sticky patches and HbS polymerisation

Question 36

How can thalassaemias occur? (2)

Answer 36

Gross deletion of one or more globin genes
Gene mutation

Question 37

Describe the 2 classes of thalassaemia.

Answer 37

a - production of a globin is deficient
b - production of b globin is deficient

Question 38

What form of haemoglobin is produced in a thalassaemia?

Answer 38

Excess B chains
Unstable tetramers of 4 B chains
HbH

Question 39

What happens to the oxygen dissociation curve in a thalassaemia?

Answer 39

High O2 affinity, reduced oxygen carrying capacity

Question 40

Why is B thalassaemia more clinically important than a thalassaemia?

Answer 40

Results in iron overload -> organ damage

Question 41

What does an excess of a chains lead to in B thalassaemia? (3)

Answer 41

Do not form tetramers
Bind to and damage RBC membranes
At high conc. form toxic aggregates
RBC are fragile and short-lived