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A. Photosynthesis is the process by which plants make ALL their food. Also the process is a source of almost ALL FOOD and OXYGEN for all other life forms. Plants literally turn sunlight energy to sugar by this process.B. The diagram of plant (Figure 10-A) shows where photosynthesis takes place and the chemicals involved.
Be able to name and designate what important chemicals enter the plant, at what location, and the chemicals formed by the process and their location at the end.
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A. Respiration is the chemical breakdown of sugar (all of which is made by photosynthesis) which releases energy used in ALL processes of the cell.1. The respiration process is described below.2. Respiration releases energy from sugar (a chemical "burning") to do the work of the cell.
It can be compared to gas burned in the automobile engine to do the work of forward motion. (See figure 10-B.)
3. It is a process that must go on ALL the time, and in ALL cells. It is continuous process of life. If a cell ceases to respire, it will soon die.
4. In higher plants, oxygen gas is required. Oxygen mainly moves into the plant through the stomates (pores or openings) in the leaf.
B. Respiration, in some ways, is like the reverse of photosynthesis.
1. Respiration: SUGAR + OXYGEN ---- yields WATER + CARBON DIOXIDE plus ENERGY for cellular needs.2. Photosynthesis: WATER + CARBON DIOXIDE + light energy ---- yields SUGAR + OXYGEN. See figure 10-C.
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The use of energy in the cell is like the use of money in an economic system.A. Photosynthesis is like earning money and storing it as starch (like having a bank account).
B. Respiration is like spending money:
1. It is necessary for processes of life; the reproduction (flowers and fruits), the repair, growth, and fighting off insects and diseases.2. The plant is on an energy "budget." It cannot make an endless supply, so energy resources are allotted to different processes.
3. (Here is an example of how energy formed by photosynthesis may be reallocated to meet plants' needs.When plants adapt to different environments, like Hawai'i, certain characteristics, like protection from grazing animals may not be needed any more. The plants may gradually (through many generations) lose the ability to make the chemicals that once protected them from grazing. The energy "saved" could go to another process, like reproduction.)Click here to leave your comments and suggestions. Learning Objectives
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