Question

Which of the following causes red colour of the blood?
A. Filerin
B. Antigen
C. Haemoglobin
D. Platelets

Answer 1

Blood is a red coloured liquid which circulates in our body. It is connective tissue that contains plasma, red blood corpuscles, white blood corpuscles and platelets. It helps to deliver oxygen and nutrients to various cells and tissues in our body.
Plasma is a liquid which is also known as fluid matrix and all the three types of cells i.e. RBCs, WBCs and platelets keep floating in it.

Complete answer: To answer this question first we need to know about all the options we are provided with.
Filerin is used in beauty products as a lips plumper that makes our lips soft and acts as a moisturizer for lips.
Antigen refers to any substance that stimulates our immune system to produce antibodies against it. It is not a medium of providing colour. An antigen can be any substance from our surroundings such as bacteria, viruses, toxins and other foreign substances, etc.
Red blood cells are red in colour due to the presence of a red pigment called haemoglobin. Haemoglobin is the iron-containing protein molecule present in RBCs. It performs an important function of carrying oxygen from lungs to the body tissues. It also performs a major role in maintaining the shape of RBCs.
Platelets (also known as Thrombocytes) are the tiny fragments of special cells which form in the bone marrow. It helps in the coagulation of blood in a cut or wound. They do not have nuclei and are colourless.

So, the correct answer is option (C) Haemoglobin.

Note: Vertebrate blood has bright red colour when its haemoglobin is oxygenated and dark red in colour when its haemoglobin is deoxygenated. Each molecule has four heme groups and its colour changes when interacted with different other molecules.
The only vertebrae present without haemoglobin is the crocodile icefish. It takes up the oxygen directly from the oxygen-rich water where it lives.