Question

Which part of the body is not made up of cells?
a. hair
b. Nail
c. Finger
d. Eye
e. None of these

Answer 1

Hint: Body is protected by external parts totally composed by fibrous proteins. The fibrous proteins are tough and give structural strength to cells and the body. These are not consisting of cells.

Complete answer:
Hair and nail are composed of fibrous protein as keratin. It is a type of fibrous protein. The keratins have evolved for strength. These proteins constitute almost the entire dry weight of hair, wool, nails, claws, quills and much of the outer layer of skin. The keratins are fibrous proteins and classified as intermediate filament (IF) proteins. All intermediate Filament proteins have a structural function. This keratin protein coiled together to form coiled coil structure. It further forms proto filament and protofibrils. A hair is an array of many keratin filaments.

Finger is a limb of the human body and a type of digit, Finger is composed of bones, muscles and skin layer. Skin is made up of three layers. The outermost layer is the epidermis. This consists mainly of cells called keratinocytes, made from the tough protein keratin. Keratinocytes form several layers that constantly grow outwards as the exterior cells die and flake of. Thus fingers consist of cells.

Eye cells are called rods and cones and primarily responsible for detecting light. They are acting as photoreceptor cells. They send signals to the brain through retinal ganglion cells (RGCs) so the brain can form our perception of images. Thus eyes also consist of cells.

Hence, the correct answer is, both a and b.

Note: Hair and nails are external appendages and consist of keratin protein. The keratin consists of alpha type. It has a complex structure as coiled coil, protofilament. They are held by disulphide bonds, which make it stronger. Thus, it helps in protection of the body. These are entirely made up of protein.