Cell Theory
Cell Structure - Cell Organelles
1. What is cell theory?
Cell theory asserts that the cell is the constituent unit of living beings. Before the discovery of the cell, it was not recognized that living beings were made of building blocks like cells. The cell theory is one of the basic theories of Biology.
2. Are there living beings without cells?
Viruses are considered the only living beings that do not have cells. Viruses are constituted by genetic material (DNA or RNA) enwrapped by a protein capsule. They do not have membranes and cell organelles nor do they have self-metabolism.
3. In 1665 Robert Hooke, an English scientist, published his book Micrographia, in which he described that pieces of cork viewed under the microscope presented small cavities similar to pores which were filled with air. Based on later knowledge, of what were the walls of those cavities constituted? What is the historical importance of that observation?
The walls of the cavities observed by Hooke were the walls of the plant cells that form the tissue. The observation led to the discovery of the cells, a fact only possible after the invention of the microscope. In that work, Hooke established the term “cell”, now widely used in Biology, to designate those cavities seen under the microscope.
4. What are the two big groups into which cells are classified?
Cells can be classified as eukaryotic or prokaryotic.Prokaryotic cell is that without a delimited nucleus. Eukaryotic cells are those with nucleus delimited by membrane.
5. Do bacteria cells have a nucleus?
In bacteria the genetic material is dispersed in the cytosol and there is no internal membrane that delimits a nucleus.
6. Are there any bacteria made of more than one cell?
There are no pluricellular bacteria. All bacteria are unicellular prokaryotic.
7. What is the plasma membrane of the cell? What are its main functions?
The plasma membrane is the outer membrane of the cell, it delimits the cell itself and
1. What is cell theory?
Cell theory asserts that the cell is the constituent unit of living beings. Before the discovery of the cell, it was not recognized that living beings were made of building blocks like cells. The cell theory is one of the basic theories of Biology.
2. Are there living beings without cells?
Viruses are considered the only living beings that do not have cells. Viruses are constituted by genetic material (DNA or RNA) enwrapped by a protein capsule. They do not have membranes and cell organelles nor do they have self-metabolism.
3. In 1665 Robert Hooke, an English scientist, published his book Micrographia, in which he described that pieces of cork viewed under the microscope presented small cavities similar to pores which were filled with air. Based on later knowledge, of what were the walls of those cavities constituted? What is the historical importance of that observation?
The walls of the cavities observed by Hooke were the walls of the plant cells that form the tissue. The observation led to the discovery of the cells, a fact only possible after the invention of the microscope. In that work, Hooke established the term “cell”, now widely used in Biology, to designate those cavities seen under the microscope.
4. What are the two big groups into which cells are classified?
Cells can be classified as eukaryotic or prokaryotic.Prokaryotic cell is that without a delimited nucleus. Eukaryotic cells are those with nucleus delimited by membrane.
5. Do bacteria cells have a nucleus?
In bacteria the genetic material is dispersed in the cytosol and there is no internal membrane that delimits a nucleus.
6. Are there any bacteria made of more than one cell?
There are no pluricellular bacteria. All bacteria are unicellular prokaryotic.
7. What is the plasma membrane of the cell? What are its main functions?
The plasma membrane is the outer membrane of the cell, it delimits the cell itself and