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The Cell

The Cell:
Talk About Multi-tasking!


The human body is made up of trillions and trillions of cells. A cell is the smallest living unit known, and is often called the “building block” of the body. This is because cells make up everything in the body. There are bone cells, blood cells, heart cells, skin cells, hair cells, brain cells, and so many, many more. Each of these cells function a bit differently, but their overall purpose is to keep the body functioning, growing, and developing properly.

Understanding what makes up a cell and how that cell works is fundamental to all of the biological sciences so we spend a little time proving very general background information.


The Cell Theory

The English scientist Robert Hooke first described cells in 1665. It took nearly two centuries following this remarkable discovery to recognize that all living things consist of cells. This formed the basis of the “cell theory”. The theory was expanded when the cell was determined to be the smallest structure capable of all of the activities that define life.

Primary among such activities is the transfer of an exact copy of genetic material to the next generation. For these reasons, the cell theory now states that all living things are cellular and that all cells come from cells. In other words, all living things are generated through the replication and division of a single parent cell.

Image courtesy of National Institute of General Medical Sciences

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Each cell has its own particular structure, but there are some general characteristics
that are found in most cells:

  1. A cell is completely contained within a plasma membrane. This membrane keeps all of the cell's contents neatly inside, while keeping out harmful substances. Inside the cell are the cytoplasm, the nucleus, and the organelles-structures that perform various functions.

  2. The cytoplasm is a gel-like substance in which the nucleus and organelles are found.

  3. The nucleus is the “brain” of the cell. It contains the genetic information in the form of chromosomes (structures that contain our genes), as well as the nucleolus, a structure that helps the nucleus function. The nucleus is completely separated from the rest of the cell by a membrane similar to the plasma membrane that encircles the cell.

  4. Each of the organelles (various cell structures) has a different function, but they all work to keep the cell healthy and help it perform its job.

  5. Outside of the cell is the extracellular membrane – more about this later.


Cell Biology

Cell biology is an academic discipline that studies cells - their physiological properties, their structure, their interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level. Cell biology research encompasses both the great diversity of single-celled organisms like bacteria and protozoa, as well as the many specialized cells in multicellular organisms like humans.

Knowing the components of cells and how cells work is fundamental to all biological sciences. Appreciating the similarities and differences between cell types is particularly important to the fields of cell and molecular biology as well as to biomedical fields such as cancer research and developmental biology.

"A cell's genetic material, its DNA, is found in its nucleus and includes a complete set of chromosomes (46 chromosomes). This genetic material controls everything the cell does including how it proceeds through the cell cycle." Quote from WikiGenetics created by Genetic Alliance"


Normal Cell Communication:

Normal cells act on each other to control their growth and other properties in balance with the entire organism. They are closely regulated by a variety of genetic and biochemical signaling processes.

Image courtesy of Dr. Roadnottaken of the Scripps Institute:
This is for reference purposes only to illustrate the complexity of the normal cell communication networks.

For example, biological feedbacks act in much the same way that a thermostat controls heat production by a furnace. Cancer is a disease of “outlaw” cells, cells that have lost their normal relationship to the whole organism so that this feedback loop is damaged.

Crucial to all normal cell growth is a communication network that functions properly. This network is an intricate collection of pathways built with interactive proteins. Along these pathways, precise protein-to-protein signaling enables a very carefully guarded regulation of growth and function. Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions.

The ability of cells to perceive and correctly respond to their internal signals as well as to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue health. Errors in cellular information processing are responsible for diseases such as cancer, autoimmunity, and diabetes. By understanding cell signaling, diseases may be treated effectively and, theoretically, artificial tissues may be yielded.

In biology, the term crosstalk refers to the phenomenon that signal components in one signal pathway can be shared between different signal pathways and responses to a signal inducing condition (e.g., stress) can activate multiple responses in the cell/organism.

Traditional work in biology has focused on studying individual parts of cell signaling pathways. Systems biology research helps us to understand the underlying structure of cell signaling networks and how changes in these networks may affect the transmission and flow of information. Such networks are complex systems in their organization and function.

Analysis of cell signaling networks requires a combination of experimental and theoretical approaches including the development and analysis of simulations and modeling.


Cancer is a Communication Failure in the cell

The genetic changes involved in cancer result in altered proteins that disrupt the cell’s communication network. In cancer, altered proteins along many different pathways cause> signals to be garbled, intercepted, amplified, or misdirected

These changes hijack what was once normal communication and use it to achieve uncontrolled tumor growth. The image below illustrates some examples of how cancer disrupts normal cellular pathways.

Image courtesy of the National Cancer Institute for reference purposes only

CISN Summary

  1. Each individual cell has an internal signaling network along extensive pathways.

  2. Cells communicate with one another by means of chemical signals.

  3. When either internal or cell-to-cell communication is damaged disease may occur including cancer.


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