Exam II Key Concepts

Exam II Key Concepts - Exam II Key Concepts Topic 6 Cells...

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Exam II Key Concepts Topic 6: Cells: the basic units of life All cells come from pre-existing cells (=Cell Theory), and therefore have in common many processes, molecules, and structures. Cell theory: cells are the fundamental units of life, all organisms are composed of cells, and all cells come from pre-existing cells. What is a cell, and what it thought to be the adaptive advantage of this? Cells are the building blocks of life. Cells contain water and the other small and large molecules. Each cells contains at least 10,000 different types of molecules, most of them present in many copies. Cells use these molecules to transform matter and energy, to respond to their environment, and to reproduce themselves. Why are cells limited in size by their surface area-to-volume ratio? Most cells are tiny. The volumes of cells range from 1-1000 cubic micrometers. Small cell size is a practical necessity arising from the change in the surface area-to-volume ratio of any object as it increases in size. As an object increases in volume, its surface area also increases, but not to the same extent. The volume of a cell determines the amount of chemical activity it carries out per unit of time. The surface area of a cell determines the amount of substances the cell can take in from the outside environment and the amount of waste products it can release to the environment. As a living cell grows larger, its chemical activity, and thus its rate of waste production and its need for resources, increase faster than its surface area. Cells must often distribute substances from one place to another within the cell; the smaller the cell, the more easily this is accomplished. Large organisms must consist of many small cells: cells must be small in volume in order to maintain a large enough surface area-to-volume ratio and an ideal internal volume. The large surface area represented by the myriad small cells of a multicellular organism enables it to carry out the many functions required for survival. What is the function of the plasma membrane, and what is it about phospholipids
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This note was uploaded on 04/03/2008 for the course BIO 181 taught by Professor Jorstad during the Fall '07 term at Arizona.

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Exam II Key Concepts - Exam II Key Concepts Topic 6 Cells...

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