Lesson 21 — Activity 1: Another Look at Energy
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Lesson 21 — Activity 1:
Another Look at Energy
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Earlier in this course, you learned how plants get energy and produce food. You also learned that unlike plants, your body cannot manufacture its own food to give you energy. You must get energy from the food you eat.
In this activity, you will look once more at what energy is and how it is transformed and transferred.
Remember that energy is something that gives things the ability to move, work, or cause changes. Energy can be transformed from one form to another, and energy can be transferred from one object to another.
Plants get energy from the sun.
You learned about this in L10 — A2. Below is a review of this process.
During photosynthesis, the chloroplasts in green plants capture energy from the sun and store it in food molecules. Plants use the energy from the sun, along with water and carbon dioxide, to make a simple sugar called glucose. A by-product of this process is oxygen. This is released from the leaves into the air. Food that the plant does not use immediately is stored for later use.
If plants make more glucose than is needed, the excess glucose is stored as starch. This is stored in the plant's leaves, seeds, stems, and roots.
Glucose is one of the main sources of chemical energy for both plants and animals. Most living things convert the chemical energy in glucose to a form they can use for their life processes. This is called cellular respiration. Below is a review of this process.
Both animals and plants use a process called cellular respiration in which the food that is produced undergoes chemical change and releases energy.
Cellular respiration takes place in the cell's mitochondrion. Remember that the mitochondrion is like a cell's power plant. The mitochondrion converts energy from the food into a form of energy that the cell
uses to grow and do its work.
It works like this:
The mitochondrion takes in nutrients (glucose and oxygen), breaks them down, and creates energy for the cell. The glucose is broken down into carbon dioxide and water. When
it does that, there is a release of energy and the organism (plant or animal) uses that energy to function.
1. Photosynthesis stores energy.
2. Cellular respiration releases energy. This released energy is the only form of energy the cell can use for all its activities.
The image below shows the connection between photosynthesis and cellular respiration. Look at the arrows,
these processes form a cycle.
People consume starch when they eat carbohydrates, such as potatoes and bread. During digestion, your body then breaks down the starch into glucose. The energy produced is used for your life processes. The mitochondria in people's cells release this energy.
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