Cell Theory Practice Questions
20 free Cell Theory practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Who first observed and described a live cell?
- A Robert Hooke (1665)
- B Anton von Leeuwenhoek
- C Matthias Schleiden (1838)
- D Theodore Schwann (1839)
Correct answer: Anton von Leeuwenhoek
While Robert Hooke first discovered cells in a cork slice, they were dead cells. Anton von Leeuwenhoek was the first to see and describe live cells like bacteria and protozoa using his improved microscope.
In 1838, Matthias Schleiden, a German botanist, examined a large number of plants and concluded that:
- A All animals are composed of cells.
- B Cells arise only from pre-existing cells.
- C All plant tissues are composed of cells.
- D Plant cell walls are absent in animal cells.
Correct answer: All plant tissues are composed of cells.
Schleiden's contribution to the cell theory was specifically focused on botany. He observed that all plant tissues are composed of cells, which was later integrated with Schwann's animal cell observations.
Theodore Schwann, after studying different types of animal cells, reported that cells had a thin outer layer which is today known as the:
- A Cell wall
- B Plasma membrane
- C Nuclear envelope
- D Glycocalyx
Correct answer: Plasma membrane
Schwann identified the thin outer boundary of animal cells. He also concluded, based on his studies on plant tissues, that the presence of a cell wall is a unique character of plant cells.
Which scientist modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape?
- A Robert Brown (1831)
- B Rudolf Virchow
- C Camillo Golgi
- D George Palade
Correct answer: Rudolf Virchow
Schleiden and Schwann did not explain how new cells were formed. Rudolf Virchow (1855) first explained that cells divide and new cells are formed from pre-existing cells (Omnis cellula-e cellula).
The statement 'Omnis cellula-e cellula' means:
- A All cells have a nucleus.
- B All cells are totipotent.
- C All cells come from pre-existing cells.
- D Cells are the fundamental unit of life.
Correct answer: All cells come from pre-existing cells.
This Latin phrase was coined by Rudolf Virchow. It provided the missing link in the original cell theory by explaining the origin of new cells through division.
Which of the following is an exception to the cell theory?
- A Bacteria
- B Fungi
- C Viruses
- D Lichens
Correct answer: Viruses
Viruses are considered an exception to the cell theory because they are sub-cellular or non-cellular entities. They do not possess a cellular machinery of their own and only show life signs inside a host.
The smallest cell, measuring only 0.3 micrometers in length, is:
- A Bacteria
- B Mycoplasma cells
- C Ostrich egg cell
- D Human red blood cell
Correct answer: Mycoplasma cells
Mycoplasmas are the smallest known living cells. They lack a cell wall and can survive without oxygen, reaching sizes as small as 0.3 micrometers.
What is the typical size range of a human Red Blood Cell (RBC)?
- A 2-3 micrometers in diameter
- B 7.0 micrometers in diameter
- C 15-20 micrometers in diameter
- D 100 micrometers in diameter
Correct answer: 7.0 micrometers in diameter
Human red blood cells are consistently about 7.0 micrometers in diameter. Their small size and biconcave shape help them navigate through narrow capillaries.
Among the following, which is the largest isolated single cell?
- A Nerve cell (neuron)
- B Human egg cell
- C Egg of an ostrich
- D Acetabularia alga
Correct answer: Egg of an ostrich
The egg of an ostrich is the largest known isolated single cell. Nerve cells are among the longest cells, but they are not the largest in terms of total volume or mass.
The shape of the cell may vary with the _______ they perform.
- A Organism
- B Function
- C Temperature
- D Age
Correct answer: Function
Cell shape is directly related to its specific function. For example, nerve cells are long to conduct impulses over distances, while RBCs are biconcave to increase surface area for gas exchange.
Both prokaryotic and eukaryotic cells contain a semi-fluid matrix where main cellular activities occur. This is called:
- A Stroma
- B Cytoplasm
- C Protoplasm
- D Hyaloplasm
Correct answer: Cytoplasm
The cytoplasm is the main arena of cellular activities in both plant and animal cells. Various chemical reactions occur here to keep the cell in the living state.
Non-membrane bound organelles found in both eukaryotic and prokaryotic cells are:
- A Mitochondria
- B Ribosomes
- C Cilia
- D Chloroplasts
Correct answer: Ribosomes
Ribosomes are non-membrane bound organelles found in all living cells. They are found not only in the cytoplasm but also within organelles like chloroplasts and mitochondria.
Which organelle is found only in animal cells and helps in cell division?
- A Centriole
- B Ribosome
- C Peroxisome
- D Nucleolus
Correct answer: Centriole
Centrioles are non-membrane bound organelles characteristic of animal cells. They play a crucial role in forming the spindle apparatus during cell division.
What is the genomic material of a prokaryotic cell called when it is not enveloped by a nuclear membrane?
- A Nucleus
- B Nucleolus
- C Nucleoid
- D Nucleosome
Correct answer: Nucleoid
In prokaryotes, the genetic material is basically naked and not enveloped by a nuclear membrane. This irregularly shaped region is called the nucleoid.
Which of the following statements about cell theory is FALSE?
- A All living organisms are made up of cells.
- B All cells arise from pre-existing cells.
- C The cell is the basic structural and functional unit of life.
- D All cells have a membrane-bound nucleus.
Correct answer: All cells have a membrane-bound nucleus.
The statement that all cells have a membrane-bound nucleus is false because prokaryotic cells (bacteria, blue-green algae) lack a nuclear membrane.
The intensive study of the cell under the electron microscope became possible only after:
- A 1838
- B 1855
- C 1950
- D 1900
Correct answer: 1950
The invention of the electron microscope and its improvement in the 1950s allowed scientists to observe the detailed internal structure and organelles of the cell.
An example of a cell that is long and branched is the:
- A Red blood cell
- B Tracheid
- C Nerve cell
- D Mesophyll cell
Correct answer: Nerve cell
Nerve cells (neurons) are some of the longest cells in the body and are often branched to receive and transmit signals to multiple other cells.
Cells which lack a well-defined nucleus and membrane-bound organelles are called:
- A Eukaryotic cells
- B Prokaryotic cells
- C Somatic cells
- D Germ cells
Correct answer: Prokaryotic cells
Prokaryotic cells (Pro = primitive, Karyon = nucleus) lack a nuclear envelope and membrane-bound organelles like mitochondria or Golgi bodies.
Which of the following scientists concluded that the presence of a cell wall is a unique feature of plant cells?
- A Schleiden
- B Schwann
- C Virchow
- D Robert Brown
Correct answer: Schwann
Theodore Schwann, an animal physiologist, observed that animal cells had a plasma membrane and also noted that plant cells were distinct because of their cell walls.
The volume of a cell is generally proportional to:
- A The size of the organism
- B The amount of DNA
- C The metabolic activity and requirements of the cell
- D The thickness of the cell wall
Correct answer: The metabolic activity and requirements of the cell
Cell size is determined by the surface area to volume ratio and the ability of the nucleus to control the cytoplasm. Higher metabolic activity often dictates specific size constraints.