Lesson 2.1 - Storing Energy from the Sun

You have learned about photosynthesis.  Photosynthesis produces glucose from carbon dioxide, water, and sunlight.  Plants can convert glucose into other compounds such as fructose and carbohydrates such as starch. 

If you eat a plant part, such as fruit, that tastes sweet as soon as you put it in your mouth, you know it contains some form of sugar such as glucose or fructose.  If you eat a plant part, such as potato that does not taste sweet, you know it contains starch or some other carbohydrate.  Plants convert excess glucose into starch and store it in this form.

You should be asking, why is that?  Why not just store the glucose?  After all, that is the form of energy the plant cells need anyhow.  If a cell needs food energy, the starch must first be converted to glucose before the cell can use it.

  1. The first reason is that the energy must be stored in a form that does not disrupt the normal working of cells.  To understand this better, look at yourself.  Your body digests food and turns it into glucose that your body cells can use as a source of energy.  But what happens if you have too much glucose in the blood?  The cells would be swimming in a sea of sugar that would disrupt how they work.  Therefore, your body takes excess sugar from the blood and converts it to fat that is stored in special fat cells.  This stored energy does not affect how the cells in your body operate, and your body stays in balance.  Plants do a similar thing.  When too much glucose is in the plant, the plant converts the glucose to a starch that stores the energy yet does not affect the balance in the plant.

  2. The second reason is that starch stores more energy than glucose for the size of the molecule.  Because starch is actually many glucose molecules packed together, starch is a more efficient way of storing energy for later use.  Imagine a large box of puzzle pieces.  The pieces take up a large space.  When you put the puzzle pieces together, the completed puzzle takes up much less space.  Similarly, the potato stored a great deal of energy in a small space. The young potato plants will have a tremendous store of energy to help them grow into plants big enough to produce their own energy.

Read Storing Energy from the Sun on page 240. 

You should review the Photosynthesis applet on your Science.Connect1 CD at this time as well.   If you don't have the CD check the provided answers and study from them.

 

Question 1. Why do plants produce glucose?

Question 2. When plants produce more glucose than they need, what happens to the excess glucose?

Question 3. Where is starch stored in a plant?

Question 4. When you eat starch or any carbohydrate, what does your body do with this type of food?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Why do plants produce glucose?

Plants produce glucose to provide the energy needed for their own life processes.

Question 2. When plants produce more glucose than they need, what happens to the excess glucose?

When plants produce more glucose than they need, the excess glucose is converted to starch (carbohydrates) and then stored in the plant.

Question 3. Where is starch stored in a plant?

Plants can store starch almost anywhere in the plant: leaves, stems, roots, and seeds.

Question 4. When you eat starch or any carbohydrate, what does your body do with this type of food?

Your body digests the carbohydrates and converts them to glucose which your body cells can use.  Excess glucose is converted to fat and stored in fat cells.  

 


Go to the next page to continue Lesson 2.