Student's Pages
Activity 15: Wondering About Photosynthesis
Activity 15 TEACHER'S PAGE
What happens to the food after it is made in the leaf?
What happens to the food after it is made in the leaf?
Each of the cells in every part of the plant needs to get some
food. Only the cells that are green can make the food. It is the green pigment (called chlorophyll) in the
leaf which is able to catch and use the energy from the sun. Can our body cells catch sunlight and use it to
make food? Why not?
The food that is made in the leaf of a plant needs to be used to
feed every cell in the plant. Some of the food that is made by the leaf cells gets used up by cells in the
leaf. These cells need energy to make food!
But some of the food travels from the leaves to all other parts
of the plant, where it can be used by plant cells for energy and growth. This is the only way cells in the
roots or the stems or the flowers can get the food energy they need.
Why can't the cells in the roots just make their own
food?_____________________
________________________________________________________________
Plants also store some of the food they make. Extra food they
make can be stored in the seeds, in the fruits and vegetables, in the roots or in the stems. Potato and
carrot plants store extra food in the roots -- we call these storage places potatoes and carrots. Some food is
stored in fruits and seeds. Seeds are the mother plant's way of storing up food to help the new, young
plant get started in life.
When plants store food, they usually change it from sugar to some
other kind of food, such as starches or fats. Animals can also change food from one kind to another. For
example, a cow eats one kind of food -- grass -- and changes it into another kind of food -- milk. But
all of the food on earth first started out as sugar made through photosynthesis in plants. This is why
scientists call plants _______________________. But animals are called consumers,
because they use the food that was produced by plants.
Draw arrows to show how you think food moves after it is made in
the leaf of a strawberry plant.
Where did the food come
from?___________________________________________
_______________________________________________________________
Experiment
Which Plant Parts Contain Food and Starch?
In this experiment, we will try to figure out which parts of the
plant contain food made by the plant during photosynthesis. The plant makes food in the form of sugar. Then
it stores extra food in different parts of the plant. Sometimes the plant changes the sugar to something else
before it stores it. It's a lot like how our body changes extra food we eat into fat. The plant sometimes
changes sugar into a material called starch.
It is easier to test for starch than to test for sugar, so we
will study which plant parts have starch in them.
Starch does have energy in it. Is it a food for the plant?
______________
Learning How to Use A Chemical to Test for Starch: Testing Foods
1. Is bread a food for you? __________
Are sugar cubes food for you? __________
Watch what happens when a few drops of a special chemical are put
on a piece of bread.
and on a sugar cube.
2. Describe what happens to the
bread.___________________________________________
Describe what happens to the sugar
cube._______________________________________
This special chemical (an iodine solution) turns black or purple
when it touches starch. Starch is an energy-providing food.
3. Think about what you observed with the bread and the chemical.
Does bread contain starch? ______
4. Do saltines contain starch? Test it! ____________
5. Where do you think the starch in bread and saltines came
from?____________
1. PREDICTING: Do SEEDS contain starch?
You will be testing the cotyledons of a bean seed and a peanut
seed to see if they have starch in them.
Do you predict that the cotyledons of the bean and peanut seeds
will have starch
in them? _________ Explain your
prediction._______________________________
_______________________________________________________________
_______________________________________________________________
2. PREDICTING: Do VEGETABLES AND FRUITS contain starch?
You will test a potato, a banana, and a pear for starch. These
are vegetables and fruits.
Do you predict that the potato will have starch in it?
_____________
Do you predict that the banana will have starch in it?
______________
Do you predict that the pear will have starch in it?
________________
Write down the reasons for your
predictions._____________________________
_______________________________________________________________
_______________________________________________________________
3. PREDICTING: Do plant STEMS contain starch?
Next you will test a different plant part for starch -- a stem.
Do you predict that the celery stem will have starch in it?
_________
Explain your
prediction.______________________________________________
________________________________________________________________
________________________________________________________________
4. TESTING: Which plant parts contain starch?
Test the plant parts and write down your observations:
PLANT PART
DOES IT CONTAIN STARCH?
Bean seed
Peanut seed
Potato
Banana
Pear
Celery
Making Sense of the Experiment
1. Which parts of the plants you tested had starch in
them?____________________
_________________________________________________________________
_________________________________________________________________
2. Can the cells in the seeds make their own food? ________ Why
or why not?
_________________________________________________________________
_________________________________________________________________
3. Where does the food stored in the peanut seed come from?
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
4. Draw arrows to show how starch reached the cotyledons in the
seeds. Where did the food come from?
_________________________________________________________________
_________________________________________________________________
5. Draw arrows to show how the starch got to the potato and to
the banana. Where did the starch come from?
________________________________________________________________
________________________________________________________________
6. Draw arrows to show how the starch got to the stem of the
celery plant.
7. If you look carefully at the cut edge of a celery stem, you
will notice little circles. These are actually long tubes that go the length of the celery stem. You may have found
that starch was stored in some of these tubes. The tubes carry food from one part of the plant to
another.
Do you think that the food in the celery stem moves up the stem or down the stem? _________
Explain your thinking.
________________________________________________
________________________________________________________________
________________________________________________________________