Question

The liquid portion of the blood is called as :
a) Plasma
b) Leucocyte
c) Serum
d) None of the above

Answer 1

Blood is a special connective tissue that consists of a fluid matrix, plasma and formed elements. The liquid portion of the blood constitutes nearly half of the blood.

Complete answer:
Plasma is a straw-coloured, viscous fluid that constitutes nearly 55 per cent of the blood. 90-92 percent of plasma is water, and the remaining 6-8 per cent are proteins.
The major proteins found in blood are fibrinogen, globulin and albumin.
Fibrinogens are needed for clotting or coagulation of blood.
Globulins are involved in the defence mechanisms of the body.
Albumins maintain the osmotic balance.
Plasma also has a small amount of minerals like $Na^+$, $Ca^{++}$, $Mg^{++}$, $HCO^{3−}$, $Cl^−$ etc.
Plasma also contains factors that are responsible for clotting blood in an inactive form.

Additional information:
Leukocytes are also known as white blood cells (WBC). They are colourless as they lack haemoglobin. They are nucleated and lesser in number than red blood cells. These cells are short-lived. There are two main categories of WBCs, namely, granulocytes and agranulocytes.
Granulocytes include Neutrophils, Eosinophils and Basophils.
Agranulocytes include Lymphocytes and Monocytes.
The serum is a fluid and solute component of blood that does not take part in blood clotting. The serum contains proteins and electrolytes, but it lacks white blood cells, red blood cells or platelets.

So, the correct answer is a) Plasma.

Note:
Plasma is the liquid portion of the blood, while serum is the plasma without clotting factors. On centrifugation, plasma is seen at the top of the test tube.