Question

Which is the correct option amongst the following sentences?
a. Nuclear membrane, chloroplast, mitochondria, microtubules, and pili are absent in prokaryotic cells.
b. Nuclear membrane, chloroplast, mitochondria, microtubules, and pili are present in Eukaryotic cells.
c. Ribosomes are 70S in prokaryotic cells and mitochondria. They are 80S in animal cell.
A. a and b are wrong, c is correct
B. a is correct, b and c are wrong
C. a and b are correct, c is wrong
D. a and c are correct, b is wrong
E. a, b and c are wrong

Answer 1

Hint: Cytology, cell biology, or cellular biology is defined as the branch of science that deals with the study of cells. Cells are the smallest unit of life. Cells are considered the functional, structural, and biological unit of all living organisms.

Complete answer:Organisms are classified based on the number of cells they are made up of. There are unicellular and multicellular. Unicellular organisms such as bacteria are made up of a single cell, whereas multicellular organisms consist of numerous cells and include plants and animals. Cells are of two types. There are eukaryotic cells and prokaryotic cells. Eukaryotic cells are mostly multicellular and have a nucleus and a definite nuclear membrane, mitochondria, chloroplast, cell wall, and nucleic acid present in them. Fungi, protozoa, plants, and animals are some organisms that are included in prokaryotic cells. Mitochondria are referred to as the powerhouse of the cell as it produces adenosine triphosphate (ATP), the energy molecule.

Prokaryotic cells on the other hand are unicellular such as bacteria and archaea and lack a nuclear membrane and mitochondria. Prokaryotic cells also lack membrane-bound organelles therefore all of their cellular components are encapsulated in the cytoplasm. They consist of a cell membrane.

Option A: The nuclear membrane, chloroplast, mitochondria, microtubules, and pili are absent in prokaryotic cells. It is correct that prokaryotes lack a nuclear membrane, chloroplast, mitochondria, and microtubules. But pili are present in prokaryotes. Pili are hair-like appendages that allow prokaryotes such as bacteria to adhere to other cell surfaces.
Option B: The nuclear membrane, chloroplast, mitochondria, microtubules, and pili are absent in eukaryotic cells. Eukaryotes consist of a definite nucleus and nuclear membrane including chloroplast, mitochondria, and microtubules. But pili are absent in eukaryotic cells.
Option C: The ribosomes are 70S in prokaryotic cells and mitochondria and 80S in animal cells. Ribosomes are a small unit involved in protein synthesis. It has been determined that all prokaryotes have 70S ribosomes and since mitochondria and chloroplast have a symbiotic relationship with prokaryotic cells, they have 70S ribosomes as well. Here S denotes Svedberg units. Eukaryotes have been found to have larger 80S ribosomes in their cytosol.
Hence option A is correct.

Note: Robert Hooke first discovered cells in 1665. In 1839, Mathias Jakob Schleiden and Theodor Schwann developed the “cell theory” stating that all organisms are composed of one or more cells. It has been estimated that cells first appeared on earth at least 3.5 billion years ago.