1. How the Body Obtains and Uses Energy
Picture from:
How the Body Obtains and Uses Energy
Copyright PEER.tamu.edu

2. Discuss: Are you an energetic person?
When do you have the most energy?
What do you do when you need to get more energy?

3. Energy Energy is all around you! You can hear energy as sound.
You can see energy as light.
And you can feel it as wind.
Tornado picture from:

4. When do you use energy? You use energy when you hit a softball.
lift your book bag.
grow.
study.
do any activity.

5. Why is energy important to our bodies?
Living organisms need energy for their bodies’ daily activities and processes.
Tiger Photo:
Gazelle Photo:

6. Try to Recall the Six Forms of Energy
The six main forms of energy are:
Heat or Thermal
Chemical
Electromagnetic
Nuclear
Mechanical
Electrical
Have students remember the six forms of energy before you show the answers. Ask them for some examples of each type. Then ask them which type of energy our bodies use. (The slide is animated to make this easy to do.)
Our bodies use Chemical Energy

7. States of Energy Potential Energy Kinetic Energy Stored energy
There are two states in which energy can exist:
Potential Energy
Stored energy
Energy that could be used
Kinetic Energy
Energy of Action or Motion
Energy that is being used
Energy bar picture:
Kids picture:

8. Energy Conversions or Transformations
Energy can be changed from one form, or state, into another. Changes in the forms or states of energy are called energy conversions or transformations.
Ask students to look at the picture and tell how energy is being converted.
The potential (chemical) energy on the tip of the match is being converted into chemical energy of burning and heat or thermal energy and electromagnetic energy (light).
The process is started by mechanical energy (friction) of the match being converted into heat or thermal energy to start the fire.

9. Chemical Energy  Mechanical and Heat Energy
An Essential Energy Conversion
Our body converts starches, sugars, fats and even proteins (chemical energy) that we eat into energy for our bodies’ daily functions (mechanical and heat—or thermal—energy).
Ask the students to tell their favorite way of getting chemical energy… in other words, what is their favorite food?
Then ask them to think about how much exercise it would take them to use all of the energy gained from that food.
Chemical Energy  Mechanical and Heat Energy

10. How the Body Obtains Energy
First, you consume energy in the form of foods. Foods are made of organic molecules.
The organic compounds in foods that can be used for energy are:
Carbohydrates
Fats
Proteins
Point out that organic molecules are made of Carbon, Hydrogen, Oxygen, and Nitrogen. They may also contain other elements like sulfur and phosphorous. If students have already learned this, then ask them to tell why the molecules pictured are called organic molecules.
Ask the students to tell what they think those molecules are used for in the body.
Discuss that Proteins are mainly used for building structures in the body like cells and organs. Proteins are usually not used for energy unless the body is very low in energy or that all of the body’s needs for building structures have been met.
Fat is also important for other reasons than obtaining energy. Fat helps the brain and nerves develop properly as well as helping the body absorb certain vitamins. Fat actually has more than 2x the amount of energy as carbohydrates and proteins.
Carbohydrates are primarily used for energy.

11. A Glucose (sugar) Molecule
Molecules are held together by an energy force. Breaking the bonds between atoms in the molecules releases that energy.
Whether or not that bond energy does anything depends on whether it can be captured and "put to work." 
The body's job is to break food down so that cells can break down some of the chemical bonds. Then that energy can be used to do things.
Any leftover energy escapes as heat.
C6H12O6
Glucose Picture from:
Ask the students to tell what they think the “balls” represent in the glucose picture. The answer is that they represent atoms of Carbon, Hydrogen, and Oxygen. Count the number of each color to get the number of atoms.
Carbon- 6 Hydrogen-12 Oxygen-6
Bond between atoms
in the molecule.

12. During the digestion process, how does the body break down foods into smaller organic compounds?
The teeth first break down the food physically into smaller pieces. The movement of the stomach and intestines also help physically break the food.
Proteins are broken down chemically by pepsin in the stomach into amino acids.
Carbohydrates are broken down chemically into sugars (monosaccharides) by enzymes found in saliva in the mouth and by enzymes in the small intestine.
Ask the students to trace the path of food through the digestive system as a review.
Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide as a source of energy.
Fats are broken down into fatty acids in the small intestines by bile from the liver.

13. These smaller molecules are transported into body cells and then go through several chemical processes that break the molecular bonds to produce ATP, a primary storage form and source of energy in the body.
These chemical processes occur in the cytoplasm and mitochondria of the cells.
Mitochondria
Cytoplasm
ATP stands for Adenosine triphosphate. ATP serves as the immediate source of energy for the mechanical work performed by muscle. By virtue of its energy-rich pyrophosphate bonds, ATP serves as a link between sources of energy available to a living system and the chemical and mechanical work which is associated with growth, reproduction, and maintenance of living substance. For this reason, it has been referred to as the storehouse of energy of living systems.
Cell picture from:
Simplified Glycolysis and Krebs Cycle from:
The link on this slide it to
Which contains a detailed lesson on this topic explaining the chemical processes only briefly mentioned here.
For more on energy use in the body please click here

14. Mitochondria (plural of mitochondrion) are the  organelles that cells use as their energy factories. Think of them as the cell's way of recharging its battery.
Artists Mitochondria picture from:
Micrograph picture of mitochondria from:
One More Thing!  Recent research has revealed that mitochondria control death of cells. When cells die, it seems that the cause arises because the membranes of mitochondria loose their voltage charge, and this in turn causes a release of certain proteins from mitochondria into the cytoplasm of the cell. These proteins trigger a series of chemical reactions that kill the cell.
An artist’s representation of a mitochondrion
An electron micrograph of a mitochondrion
A mitochondrion is an oval bag that is filled with membranes. Mitochondria are so small that you can only see them with the high-power magnification of an electron micrograph.

15. Stop and Think: What is an energy conversion or transformation?
What energy conversion is essential for the human body?
Summarize how humans get their energy from food. Be sure to include the structures in the body that are responsible for this process.

16. Calories
Calories are a unit of measurement of food energy. They measure the amount of potential heat energy contained in the chemical bonds of a food.
People need a certain amount of calories per day.
For the average teenage girl, the recommended daily allowance is 2200 calories. The average teenage boy needs calories.
Ask students why they think boys need more calories than girls.
Answer: The “average” man has percent more lean tissue (muscle) than a woman of similar size and age, and thus a lower body fat percentage. Muscles use more calories. This alone means that a man's average calorie needs are about 5-10 percent higher than a woman's calorie needs.
The exception is pregnancy and breast-feeding, when a woman's calorie needs increase. Typically by an average extra 300 calories/day when pregnant and 500 calories/day when breast-feeding.

17. Calories add up fast!
A large cheeseburger, fries, and a soda can add up to more than 1,390 calories.
That’s more than half
of the calories that
most teens need in one
day! This is not a good deal for your body because this meal does not contain many of the other nutrients your body needs (besides calories).

18. Our Energy Use Must be Balanced!
The amount of energy that comes into our body should be equal to the amount of energy that we use.
If it is not, we STORE the extra (unused) energy.
The main way the body stores excess energy is in the form of fat.
Did I eat ALL of that?
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19. Energy Imbalance Causes Problems
Obesity
A person has traditionally been considered to be obese if they are more than 20 percent over their ideal weight. That ideal weight must take into account the person's height, age, sex, and build.
If their Body Mass Index (BMI) is between 25 and 29.9 a person is considered overweight. If their BMI is 30 or over, the person is considered obese.
BMI Formula BMI = ( Weight in Pounds / ( Height in inches ) x ( Height in inches ) ) x 703
BMI Calculator

20. Obesity is a problem in people and pets!
Childhood obesity has more than tripled in the past 30 years. The prevalence of obesity among adolescents aged 12 to 19 years increased from 5.0% to 18.1%.
An estimated 51.5% of dogs and cats in the United States are overweight or obese.
Dog picture from:
Picture of children from:
Childhood obesity statistics from Centers for Disease Control and Prevention

21. Common Health Risks of Obesity
Osteoarthritis
Type 2 Diabetes
Respiratory disorders
Hypertension (high blood pressure)
Heart Disease
Many Forms of Cancer

22. How to keep Energy Balanced:
The best way to balance your energy is to find out how much energy is used by the body each day and…..
Eat only enough calories to equal that amount of energy.
See Energy Balance Activity included in this lesson.
Energy Used in a Day
Energy Consumed
in a Day

23. Special Considerations for Teens
Teens have a little higher energy requirement than adults.
Can you guess why?
Growth-Nutrients and Calories

24. The answer is that they are growing!
Growth requires energy and healthy nutrients from foods.
As a teen, you must choose wisely so you can reach your potential!
Pyramid picture from:

25. Can you recall? What are calories?
How is extra energy stored in our bodies?
What are some risks associated with obesity?
What is meant by “energy balance” in the body?