Metabolic Energy Cycle
Home Table of Contents Preliminary Information General Characteristics Metabolic Energy Cycle Structural Features Carbohydrate Cycle Wrap-Up

 

Photosynthesis
Respiration
Anaerobic Reactions
Carbohydrates vs Fats

Metabolic Energy Cycle

In this section we will take a look at how carbohydrates, glucose in particular, fit in to the overall energy scheme of things. (This diagram is also shown in Example 4 in your workbook.)

Energy cycle diagram (ex. 4). [67004.jpg]

 

Glucose and Energy

Glucose, through a sequence of steps, can be worked into the citric acid cycle to generate carbon dioxide, water and energy. This process depends on oxygen being available and this overall process is referred to as respiration. The respiration process is used by both plants and animals alike.

The water and carbon dioxide formed by respiration can be converted into oxygen and glucose by plants in a process that is called photosynthesis. This is a significant part of the interdependence of plants and animals.

Energy cycle diagram denoting respiration and photosynthesis portions. [67006.jpg]

You can see that the energy scheme of things is a cyclic process.

Glucose and Related Chemicals

Plants can work with water and carbon dioxide and use the energy from sunlight to convert them into oxygen and glucose. Plants can use that glucose for a number of things. One, of course, is that they can use it to derive energy.

They can also make other chemicals from the glucose. They can also use the glucose to make cellulose as a structural material. Any excess glucose can be converted into starch to be saved and used later when more glucose is needed, either for additional growth, additional chemicals, or additional energy.

Energy cycle diagram showing related chemicals. [67007.jpg]

Animals also can use glucose to make other chemicals. We can store excess glucose in the form of glycogen for short-term future energy use, or convert it into fat as long-term storage for future energy use. These compounds can be broken back down into glucose to run it through the respiration process to free up some energy to carry on the functions that are needed.

I think you can see that glucose has a fairly central role in the life process, in particular, the energy aspect of living things. In the other pages of this section we will look at the photosynthesis and respiration portions of this process in more detail.

 

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