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C1. The cell is the unit of structure and function of most organisms.


Student Outcome: C1.1

Understand that the cell is the smallest independent unit of life.


All independent life on this planet is cellular. The living cell is the smallest unit capable of showing all the "signs and symptoms" that define the phenomenon we call "life".


Source: http://www.brooklyn.cuny.edu/bc/ahp/LAD/C9/C9_reproduction.html


Very interesting site with a lot of detail about cells. Go here or die (just joking of course).


This site from the University of Utah shows the size of cells compared to other common items. Take a look,, why don't you?


A conventional definition of Life


Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life exhibits the following phenomena:



  1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, sweating to cool off.
  2. Organization: Being composed of one or more cells, which are the basic units of life.
  3. Metabolism: Production of energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
  4. Growth: Maintenance of a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular species begins to multiply and expand as the evolution continues to flourish.
  5. Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
  6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun or an animal chasing its prey.
  7. Reproduction: The ability to produce new organisms. Reproduction can be the division of one cell to form two new cells. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from at least two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.


Source: http://en.wikipedia.org/wiki/Life


Here is basically the same information but in pictures!



Student Outcome: C1.2

Explain the significance of surface area to volume ratio.


Why are single-celled organisms so small? Tiny organisms have to take in food, water, gases, and chemicals, and they have to excrete waste products. They are full of organic molecules that have to be moved around and processed. In small cells, all parts of the cell are near the cell membrane, and chemical exchanges with the environment are simplified. As single cells grow larger, the contents increase in volume, and making everything work together becomes more complex. The cell membrane, the interface between the living cell and the world, does not increase in area as quickly as the volume of the cell contents. At some point, the structures and processes in the cell will become inefficient if the cell becomes too large.


A sphere is a strong, efficient shape. Cells that are shaped like tiny bubbles contain the greatest volume for their surface area. However, cells come in a great variety of shapes. We have seen many cells that are shaped like tiny rods. Rod-shaped cells will have more surface area compared to their contents than spherical ones. However, as cells evolve to increase their surface area, they risk becoming increasingly fragile.


Source: curriculum.calstatela.edu


Go to this site for a more detailed explanation of this important idea.


Go here to see an animation calculating surface area and volume.


This interactivity will change the three dimensions of a rectangle and show you the surface area and volume calculations. Try starting with 1 x 1 x 1 cm cube and then adding one to each dimension - what happens to the SA/V ratio?


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