66 PHARMACEUTICAL BOTANY 
stomata and passes into the intercellular-air-spaces of all of the 
organs which communicate one with another throughout 
the entire plant. It diffuses through the cell walls lining these 
spaces into the cells. Here it unites with the food materials 
present, oxidizing a portion of them. Oxidation of glucose, etc. 
is a breaking down process, similar to the combustion of fuel in a 
furnace, but less intensive and not accompanied by light. The 
chief products of oxidation are carbon dioxide and water. 
The oxidation of food materials within the cells of organisms 
is called ResprrATION. ‘The carbon dioxide resulting from this 
process diffuses through the walls of the cells into the intercellular- 
air-spaces and finally passes out through the stomata. When 
food materials such as grape sugar undergo oxidation, their 
stored-up energy (potential energy) is set free as energy in motion 
(kinetic energy). This energy is utilized by the protoplasm of 
the cell in carrying on its various kinds of works. 
Respiration may be expressed by the following equation: 
CsHiO, + 602 = 6CO;, + 6H.O 
Glucose Oxygen Carbon Water 
Dioxide 
Respiration differs from photosynthesis in the following 
particulars: 
RESPIRATION PHOTOSYNTHESIS 
1. It occurs in all living cells. 1, It occurs only in cells containing 
chlorophyll. 
2. It takes place during the day and the 2. It takes place only during the day 
night. under natural conditions. 
3. Oxygen is absorbed and carbon 3. Carbon dioxide is absorbed acd 
dioxide is set free. oxygen is set free. 
4. Carbohydrates are combined with 4. Carbohydrates are formed. 
oxygen and oxidized. : 
5. Potential energy is released from the 5. Kinetic energy is stored in the f, om 
food molecules as kinetic energy. molecules as potential Sahay. 
6. It is a destructive process. 6. It is a constructive Process, 
There is another process which goes on in the various cells of 
these organs. It will be recalled that the surplus glucose is 
stored up in the form of starch by the leucoplasts and that surplus 
proteins are also stored. These stored foods are not in the — 
whereby ey can be used by the protoplasm when need a c.. 
