Biology Chapter on Unicellular Organisms

What is considered the fundamental structural and functional unit of all living organisms?

Who first observed and described a live cell?

Which scientist discovered the nucleus within the cell?

What unique characteristic did Schwann attribute to plant cells?

Which of the following is a part of the cell theory as understood today?

What does the term 'Omnis cellula-e cellula' imply?

Which of the following best describes the observations made by Schleiden regarding plant cells?

In what year did Matthias Schleiden propose his observations about plant cells?

What structure serves as the outer boundary for a typical plant cell?

Which type of cells contain membrane-bound organelles?

What is the main function of cytoplasm in eukaryotic and prokaryotic cells?

Which of the following organelles is found in both plant and animal cells?

Which structure in animal cells assists in cell division?

What distinguishes prokaryotic cells from eukaryotic cells?

What is the size of Mycoplasmas, the smallest cells?

Which organelle is involved in the energy generation in eukaryotic cells?

Unicellular Organisms

Unicellular organisms can exist independently and perform essential life functions.
A complete cell structure is necessary for independent living; thus, the cell is the fundamental unit of life.

Historical Discoveries

Anton Von Leeuwenhoek first observed and described live cells.
Robert Brown discovered the nucleus within the cell.
The invention and enhancement of microscopes, especially the electron microscope, revealed intricate cell structures.

Cell Theory

Matthias Schleiden (1838) concluded that all plants are made of cells forming tissues.
Theodore Schwann (1839) studied animal cells, identifying the plasma membrane and noted the unique presence of cell walls in plant cells.
Schleiden and Schwann formulated the initial cell theory, positing that plants and animals are composed of cells.
Rudolf Virchow (1855) added that new cells arise from pre-existing cells, refining the cell theory to its modern understanding:
- All living organisms consist of cells and their products.
- All cells originate from pre-existing cells.

Overview of Cells

Onion cells represent typical plant cells with a distinct cell wall and membrane, while human cheek cells have a flexible outer membrane.
Each cell contains a nucleus that houses chromosomes and genetic material (DNA).
Eukaryotic cells have membrane-bound nuclei; prokaryotic cells do not.
Both cell types have cytoplasm, a semi-fluid matrix where cellular activities occur, crucial for maintaining life.
Eukaryotic cells possess membrane-bound organelles:
- Endoplasmic reticulum (ER)
- Golgi complex
- Lysosomes
- Mitochondria
- Microbodies
- Vacuoles
Prokaryotic cells lack these organelles but contain ribosomes, non-membrane-bound structures present in all cells, including in chloroplasts, mitochondria, and on rough ER.
Animal cells contain centrioles, which play a vital role in cell division.
Cell size, shape, and activities vary significantly:
- Mycoplasmas: smallest cells, only 0.3 µm.
- Bacterial cells also exhibit diverse structures and functions.

Explore the fascinating world of unicellular organisms, which can independently sustain life and perform essential functions. This quiz covers foundational concepts such as the cell's structure and role, and historical discoveries by scientists like Anton Von Leeuwenhoek and Robert Brown. Test your understanding of these vital biological concepts!