The Three Concepts Of Cell Theory

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1.1 Introduction:
Both living and non-living things are composed of molecules made from chemical elements such as Carbon, Hydrogen, Oxygen, and Nitrogen. The organization of these molecules into cells is one feature that distinguishes living things from all other matter. The cell is the smallest unit of matter that can carry on all the processes of life.
The three principles define cell theory:
1. All living things are composed of one or more cells.
2. Cells are the basic units of structure and function in an organism.
3. Cells come only from the replication of existing cells.
Most cells are small
Prokaryotic: 1-10 µm
Eukaryotic: 10 - 100 µm (1 µm = .001 mm)
Shape of cell: Cells come in a variety of shapes – depending on their function:-
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1.2 Theory of Cell:
1. Cells are the fundamental unit of life - nothing less than a cell is alive.
2. All organisms are constructed of and by cells.
3. All cells arise from preexisting cells. Cells contain the information necessary for their own reproduction. No new cells are originating spontaneously on earth today.
4. Cells are the functional units of life. All biochemical processes are carried out by cells.
5. Groups of cells can be organized and function as multicellular organisms
6. Cells of multicellular organisms can become specialized in form and function to carry out subprocesses of the multicellular organism.
1.2.1 The Cell Membrane:
1. A cell cannot survive if it is totally isolated from its environment. The cell membrane is a complex barrier separating every cell from its external environment.
2. This "Selectively Permeable" membrane regulates what passes into and out of the cell.
3. The cell membrane is a fluid mosaic of proteins floating in a phospholipid
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The control center or integration center receives and processes information from the receptor. And lastly, the effectors respond to the commands of the control center by either opposing or enhancing the stimulus. This is an ongoing process that continually works to restore and maintain homeostasis. For example, in regulating body temperature there are temperature receptors in the skin, which communicate information to the brain, which is the control center, and the effectors is our blood vessels and sweat glands in our brain. Because the internal and external environment of the body is constantly changing and adjustments must be made continuously to stay at or near the set point, homeostasis can be thought of as a synthetic

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