CELL GROWTH, DEVELOPMENT, AND REPRODUCTION



(Background Picture...prostate cancer cell metastasizing...the long, narrow tube like structure connecting the two bright white regions is how these cancer cells create highways which allow them to travel and invade other body organs)



At the cell level, these are important functions: 1) the way cells get and use energy; 2) growth--the process by which food and other raw materials become part of the cells; 3) reproduction--the ability of cells to give rise to more cells.








When cells take in simple food molecules from the bloodstream, some are used as energy source by the cell and other materials become part of the cell itself. Once the cell reaches a certain size, age and is surrounded by the right materials, cell division takes place. In mulitcellular organisms, overall body growth is the result of these cell divisions. The growth of multicellular organisms is primarily the result of an increase in the numbers of cells, not a change in individual cell size.





Water, proteins, fats / lipids, carbohydrates, and nucleic acids (DNA / RNA) enter cells through the cell membrane and are used as: 1) building blocks to make complex structures (proteins/fats); 2) sources of energy to keep the cell alive (carbohydrates / fats); 3) template for building complex proteins (DNA / RNA); 4) medium for reactions to take place in the cell (water).



Green plants and a few other kinds of organisms are able to make their own food using sunlight, water, carbon dioxide and chlorophyll in a process called photosynthesis. These cells are adapted to complete the photosynthetic process because they contain specialized organelles called chloroplasts. Inside each chloroplast is the chemical called chorophyll (green) that literally uses the sun's light to power photosynthesis. The sole purpose of the process of photosynthesis is to make food for the organism. All other forms of life--including the cells in your body--depend on plant cells for the food they make in the process of photosynthesis. This food is used for cell growth, development, and reproduction.