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Name _____________________________ Date ___________________________ Pd. ______
Directions: Read the entire packet and use the information to answer the questions on the
last page.
What is Energy? Energy causes things to happen around us. Look out the window. During the
day, the sun gives out light and heat energy. At night, street lamps use electrical energy to light
our way. When a car drives by, it is being powered by gasoline, a type of stored energy. The food
we eat contains energy. We use that energy to work and play.
Energy Is the Ability to Do Work.
Energy can be found in a number of different forms. It can be chemical energy, electrical
energy, heat (thermal energy), light (radiant energy), mechanical energy, and nuclear energy.
Stored and Moving Energy
Energy makes everything happen and can be divided into two types:
Stored energy is called potential energy.
Moving energy is called kinetic energy.
With a pencil, try this example to know the two types of energy.
Put the pencil at the edge of the desk and push it off to the floor. The moving pencil uses kinetic
energy. Now, pick up the pencil and put it back on the desk. You used your own energy to lift
and move the pencil. Moving it higher than the floor adds energy to it. As it rests on the desk,
the pencil has potential energy. The higher it is, the further it could fall. That means the pencil
has more potential energy.
Changing Energy
Energy can be transformed into another sort of energy. But it cannot be created AND it cannot
be destroyed. Energy has always existed in one form or another.
Here are some changes in energy from one form to another.
Stored energy in a flashlight's batteries becomes light energy when the flashlight is turned on.
Food is stored energy. It is stored as a chemical with potential energy. When your body uses
that stored energy to do work, it becomes kinetic energy.
If you overeat, the energy in food is not "burned" but is stored as potential energy in fat cells.
When you talk on the phone, your voice is transformed into electrical energy, which passes over
wires (or is transmitted through the air). The phone on the other end changes the electrical
energy into sound energy through the speaker.
A toaster changes electrical energy into heat and light energy. (If you look into the toaster, you'll
see the glowing wires.)
A television changes electrical energy into light and sound energy.
The capture and use of energy in living systems is dominated by two processes:
photosynthesis and respiration. Through these two processes living organisms are able to
capture and use all of the energy they require for their activities.
Plants can capture the electromagnetic energy from the sun by a chemical process called
The overall chemical reaction involved in photosynthesis is:
6CO2 + 6H2O (+ light energy)
C6H12O6 + 6O2.
In simple terms, we can say it the following way
Carbon Dioxide + Water (+ sun energy)  Glucose + Oxygen
The product of photosynthesis is the carbohydrate glucose and oxygen which is released into
the atmosphere. All of the sugar glucose is produced in the specialized photosynthetic cells of
plants and some other organisms. Glucose is produced by chemically combining carbon dioxide
and water with sunlight. This chemical reaction is catalyzed (make happen) by chlorophyll
acting in concert with other pigment, lipid, sugars, protein, and nucleic acid molecules.
Sugars created in photosynthesis can be later converted by the plant to starch for storage, or it
can be combined with other sugar molecules to form specialized carbohydrates such as
cellulose (remember this molecule?), or it can be combined with other nutrients such as
nitrogen, phosphorus, and sulfur, to build complex molecules such as proteins and nucleic
In general, animals cannot produce their own energy via photosynthesis. Instead, they capture
their energy by the consumption and assimilation of the biomass of plants or other animals.
Thus, animals get the energy they need for maintenance of their bodies tissues, growth, and
reproduction indirectly from photosynthetic organisms.
The oxidation of sugar by organisms is called respiration. This process occurs in both plants
and animals. In most organisms, respiration releases the energy required for all metabolic
processes. This chemical reaction can be described by the following simple equation:
C6H12O6 + 6O2 >>> 6CO2 + 6H2O + released energy
One of the products of respiration is energy, which is released via the chemical decomposition
of glucose. Other products of this chemical reaction are carbon dioxide (CO2) and water
Energy Questions
Name _________________________________
1. What do living organisms need energy for?
2. What are the two main forms of energy and provide two examples of each.
3. What are the reactants and products of photosynthesis?
4. What are two things plants will do with the sugars they produce during photosynthesis?
5. What are the reactants and products of cell respiration?
6. What relationship exists between the reactants and products of photosynthesis and cell
respiration? Using the sun, chloroplast and mitochondria pictures below, diagram this
relationship. Make sure you show where the reactants and products of photosynthesis
and cell division are coming and going!
7. Explain why we can say that even though animals are not photosynthetic, they are almost
entirely dependent on the sun for energy?
8. If a meteor impacted the earth and caused the atmosphere to fill with a dark cloud of dust
that blocked a significant amount of sunlight from hitting our planet, what impact do you
think it might have on the plants and animals on our planet? Make sure you explain your
9. There is a growing concern about rising CO2 levels in our planet’s atmosphere. What do
you think might be a reason for this increase? What do you think might we consider doing
to help eliminate some of the excess C02?