Cell Metabolism is a Defining Feature of Life
Even Living Cells Need Nurishment in Order to Function
Sep 27, 2009
Cells are the smallest living things and all organisms are composed of cells. Bacteria are single cell entities, they are prokaryotes, which means they have no nucleus.
Three Attributes of Life
Metabolism is one of the three attributes which define life. A living entity at some point in its life cycle will:
- Metabolize
- Grow, offspring are initially smaller than parents
- Reproduce, only mature organisms reproduce.
Many living things (such as people) do not grow and reproduce all the time, but metabolism is constantly taking place in almost all living things (a rare exception is the Brine Shrimp).
Animals, plants, bacteria and all cells have a life cycle which includes these three attributes.
What Does Metabolism Mean?
Metabolism is the overall term for all the chemical transformations which take place within a living organism, it includes:
- obtaining energy by feeding either through eating or photosynthesis,
- releasing energy through respiration (not breathing, but the opposite of photosynthesis).
Metabolism enables an organism to achieve the following:
- body maintenance
- body repair
- growth.
Body maintenance is the process of getting rid of old waste products and replacing with new, for example, millions of human body cells are dying and being replaced every second. An example of body repair would be new human skin replacing the old cuts and grazes.
What is Cell Metabolism?
Metabolism takes place within cells. As stated, each cell is a living unit. The external surface of a cell is its membrane which is very thin but restricts molecules moving in and out of the cell. It is selectively permeable so that it can control which molecules pass through it. Most metabolism takes place in the cytoplasm, i.e., everything within the membrane except the cell nucleus.
Note, a molecule is the smallest possible particle of a chemical and it is comprised of just a few atoms (e.g. oxygen molecules have 2 oxygen atoms; water molecules have 3 atoms).
Only some cells in an organism will may be directly involved in feeding (e.g. photosynthesis), so there will be a mechanism for the nutrients to be shared among all the living cells within the body.
Cell Metabolism
The general public are familiar with the word metabolism used in relation to weight gain, loss and diet. It refers to a whole range of chemical transformations that take place within the body. All living things including cells metabolize, which means they obtain material ad energy through chemical transformations.
Source:
Murphy P, et al (2002), “Unity Within Diversity,” S103 Discovering Science Block 4, The Open University, Milton Keynes, UK
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