Question

Which of the following structures is absent in a mature mammalian RBC?
a. Nucleus
b. Endoplasmic reticulum
c. Ribosomes.
d Mitochondria
A. a and c
B. b and c
C. a, c, and d
D. a,b,c and d

Answer 1

Hint: In mature mammalian RBC the nuclei, mitochondria, rough endoplasmic reticulum, and the ribosomes as they do not contain DNA.

Complete answer: The mature mammalian RBC lacks the membrane-bound cell organelles. Their RBC is the biconcave, circular, non nucleated cell.
They cannot synthesize RNA nor they synthesize the new proteins and have a short lifespan. The mature red blood cells in the mammalian circulate about 100-120 days in the body and then it is removed by the spleen. It loses mitochondria at phase three of erythropoiesis.
The endoplasmic reticulum is absent because it reduces the surface to volume ratio which allows more RBC to accumulate.
The RBC initially contains a nucleus but loses it as they mature which increases the efficiency of the cell to carry oxygen.

Additional information: A normal human red blood cell has a disk diameter of approximately 6.2–8.2 µm and a thickness at the thickest of 2–2.5 µm and a minimum thickness in the centre of 0.8–1 µm, and are much smaller than most other human cells.
These cells have an average volume of about 90 fL with a surface area of about 136 μm2 and can swell up to a sphere shape containing 150 fL, without membrane expansion.

Hence, the correct option is ‘D’

Note: In mammals, the Red blood cells lack a cell nucleus i.e. it is anucleate, they are red as they lack mitochondria, they are the site of anaerobic respiration.