ICSE 2018: Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow

ICSE 2018

Q. Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow: [5 marks]

(i) Name the compound numbered ‘1’ to ‘4’. 

(ii) Mention two structural differences between the parts ‘1’ and ‘2’. 

(iii) Name the soluble protein found in part ‘4’ which forms insoluble threads during clotting of blood. 

(iv) What is the average lifespan of the component numbered ‘1’? 

(v) Component numbered ‘1’ do not have certain organelles but are very efficient in their function. Explain

Solution:

This 5 marks question based on the diagram of Human Blood Smear and was asked by ICSE board in the year 2018 in SECTION-II. 

The question tested the knowledge of students on the: 

• What is different components of blood?
• How is structure of RBC differs from that of WBC?
• During the course of evolution, how has RBC made itself more efficient in transport of oxygen?
• Functions of components of blood

Let's begin with solving the above mentioned questions:

(i) The compound numbered 1 to 4 are:

1. Red Blood Cells (RBC) or Erythrocytes

2. White Blood Cells (WBC) or Leukocytes

3. Blood Platelets or Thrombocytes

4. Plasma

(ii) The two structural differences between RBC and WBC are:

    a) RBC are biconcave in shape where as WBC are irregular in shape.

    b) RBC lack nucleus whereas WBC have nucleus.

(iii) The soluble protein found in part ‘4’ (Blood Plasma) which forms insoluble threads during clotting of blood is Fibrinogen.

(iv) The average life span of component numbered ‘1’ (RBC) is 120 days.

(v)  Component numbered ‘1’ (RBC) do not have certain organelles but are very efficient in their function. 

RBC have no nucleus, mitochondria and endoplasmic reticulum yet they are very efficient in their function of transporting oxygen in body as :

    a) Lack of nucleus makes them biconcave shaped, thus increasing the surface to volume ratio for more absorption of oxygen and transporting it.

    b) Lack of mitochondria means RBC will themselves not be consuming any oxygen and will transport and deliver all the oxygen absorbed by their surface.

    c) Lack of endoplasmic reticulum makes them more flexible to travel through narrow capillaries.