PPT
Energy in the Body
Developer Notes
Version Date
03
2004/06/24
Who
Sc
Revisions
Minor editing
Goals
To trace energy back to its original source
To understand the concept of calories
To understand why we need energy
Concepts and Skills Introduced
Area
Physiology
Physiology
Physiology
Concept
Energy is required for bodily systems
A kilocalorie is the measure of energy taken in or expended by the body
Cellular respiration releases energy from food into a useable form
Time required
1 class period
Warm-up Question
Where does the energy that you use in your body come from?
Presentation
The first reading introduces energy needs in the body. The second reading expands on nutrition
and discusses other materials we need from food.
This discussion introduces/supports the first law of thermodynamics- that in a closed system,
energy is conserved—that is it is neither created nor destroyed, although it can be changed in
form.
Begin with the warm-up question. Most students may say things like from sugar or from food. A
follow up question, then should be “where does the food get the energy?”
Plants convert solar energy into useable stored sugar energy.
Animals get their energy by eating those stored sugars.
Animal and plant bodies release the energy they need by performing a series of complex
reactions to break the sugar and release energy.
So, we can trace the energy that we use in our bodies back to the sun. Most energy sources on
earth are sun-driven.
Can you think of one that is not? (Examples may include nuclear power- energy released by
splitting atomic nuclei, chemotrophs in deep sea hydrothermal vents- use chemical energy, plate
tectonics- driven by energy remaining from asteroid collisions that formed the earth)
What do we use the energy we consume for?
533557441
eb
Page 1 of 4
PPT
Energy in the Body
Work done in your body is chemical work, although there are special categories of chemical
work that are grouped separately. These are transport and mechanical work. Chemical work is
carried out by cells doing maintenance and growth; when components are synthesized and
broken down. Transport work is used to pump substances across membranes (active transport)
when they do not move on their own. Mechanical work is accomplished by muscular contraction,
but the contraction itself is chemical in nature in the individual muscle cells.
How do we know how much energy we need?
We measure food energy in the form of calories. A calorie is a simple way of keeping track of
energy intake and output. A calorie is the amount of energy needed to raise 1 gram of water 1
degree Celsius. The calories we talk about in our diet are actually kilocalories, but we call them
Calories (with a capital C). You need an average amount of kilocalories to keep yourself going.
Too much and you start to store energy as fat. Too little and you start to break down things like
muscle tissue.
533557441
eb
Page 2 of 4
PPT
Energy in the Body
Reading
Where does the energy that you use in your body come from?
We can trace the energy that we use in our bodies back to the sun:
Plants convert solar energy into useable stored sugar energy (what is this process called?).
Animals get their energy by eating those stored sugars.
Animal and plant bodies release the energy they need by performing a series of complex
reactions to break the sugar and release the energy stored within.
Most energy sources on earth are sun-driven.
What are some examples of sun-driven energy sources?
Can you think of one that is not?
What do we use the energy we consume for?
Work done in your body is chemical work, although there are special categories of chemical
work that are grouped separately. These are transport and mechanical work. Chemical work is
carried out by cells doing maintenance and growth; when components are synthesized and
broken down. Transport work is used to pump substances across membranes (active transport)
when they do not move on their own. Mechanical work is accomplished by muscular contraction,
but the contraction itself is chemical in nature in the individual muscle cells.
How do we know how much energy we need?
We measure food energy in the form of calories. A calorie is a simple way of keeping track of
energy intake and output. A calorie is the amount of energy needed to raise 1 gram of water 1
degree Celsius. The calories we talk about in our diet are actually kilocalories, but we call them
Calories (with a capital C). You need an average amount of kilocalories to keep yourself going.
Too much and you start to store energy as fat. Too little and you start to break down things like
muscle tissue. Your heart is a muscle- do you want your heart muscle broken down because you
didn’t take in enough energy to keep yourself going?
Exercises
1. Oil and gas are what we call fossil fuels, because they are the remains of animals and
plants that died long ago. Where does the energy that is released when we burn oil come
from?
2. There are several theories about why Earth is the only planet in our solar system with
abundant life. Most of them have to do with location. Why might our location in the solar
system be important to sustaining life?
3. Why do you continue to burn calories even when you are sleeping?
4. What kind of work is being done when your heart beats? When new red blood cells are
being synthesized?
5. Anorexia nervosa is an eating disorder where the victims do not consume sufficient
calories to maintain their bodies. Sufferers of Anorexia occasionally die from heart
attacks. Why is this?
533557441
eb
Page 3 of 4
PPT
Energy in the Body
Project
How many calories a day do you need to consume to keep yourself going? Use the activity table
to figure out. You will have to estimate what activities you do, and how long you do them, but
you can figure out approximately how many calories of energy you’re burning each day.
533557441
eb
Page 4 of 4