Name: __________________________________________________________ Date: ______________________________ Period: _______________
Standard 3: Energy Flow- I can demonstrate how living things are composed of cells that have internal
processes that assemble, use and break down molecules to carry out life functions
Learning Target 3.1: I can describe how a cell uses glucose from food to create usable energy
Day 1 Success Criteria:
- I can identify the basic structure of nutrients in my food
- I can categorize nutrients in food based on common structures
- I can begin to follow the breakdown of food molecules within my body
Day 2 Success Criteria:
- I can identify the key molecules that nutrients in food are broken into
- I can identify the key molecules that components in food are reassembled as
- I can describe the basic intake, breakdown and build-up of nutrients in a living organism.
PART 1: WHAT IS FOOD FOR ANIMALS? Organisms are constantly interacting with each other. Sometimes
chimpanzees will groom each other. Sometimes birds will fight over the same resources. Sometimes, an
alligator will eat a bison. For this unit, we will focus on organisms and what they eat. Think: What benefit
does one organism get from eating or consuming another organism?
In this unit, we will focus specifically on how animals benefit from eating other organisms, or (in other words)
how animals benefit from eating food. In this first activity we consider what makes up the food animals
consume.
Initial Ideas- Answer the following questions using COMPLETE SENTENCES that rephrase the question in
your answer:
1. Do you think that all food is basically composed of the same ‘stuff’ or is it composed of all kinds of different
materials?
2. If you think that food is made of the same stuff, what do you think that stuff is? If you think that food is
made up of different types of materials, what general kinds of materials do you think food is made of?
Collecting and Interpreting Evidence
Imagine eating a pizza with all the works. Also,
imagine if you could ‘see’ all the food molecules
that make up that pizza just after it entered your
mouth. Those molecules might look like what you
see in Figure 2-1.
Group the molecules that you see in Figure 2-1 into
2 to 4 groups (based on any criteria that you would
like) and then fill in the similarities and differences
tables on the next page.
Table 2-1: Similarities (use Figure 2-1 to complete)
Group
Name
Molecules in Group
List by number
What are the characteristics that the molecules in this group have that
are similar to each other?
A
B
C
D
Table 2-2: Differences
Group
Name
Molecules in Group
List by number
What are the characteristics that the molecules in this group have that
are different from each other?
A
B
C
D
Food Molecules- a deeper look
From early times, man undoubtedly noticed that the food he was preparing differed widely in materials and
properties. For example, there was a sweet tasting substance that could be found in honey and fruits. Perhaps
as early as 400 BC this sweet substance was purified into what we now know as sugar. Also, early on in
history, man was aware that there was a white, tasteless substance that could easily be powdered. Further, it
seemed to be a major component of such grains as wheat and rice. It is now called starch. Sugar and starch are
components of a broader group of molecules called carbohydrates.
Sugars are often called simple carbohydrates because they are relatively small and have relatively simple
chemical structures. One sugar that is typically found in our blood (but can also be found in our food) is
glucose. Its simple chemical structure is often represented as a single hexagon. Other common sugars are
sucrose (table sugar) and fructose.
1.
2.
What substance in Figure 2-1 might be a sugar molecule? Number _________.
What is your evidence?
Sugars, particularly glucose, are often linked together like boxcars in a train to form molecules like starch.
Starch is typically hundreds to thousands of glucose molecules linked together. Long chained molecules like
starch are often called complex carbohydrates. Simple carbohydrates and complex carbohydrates are the
two major subdivisions of carbohydrates.
3.
4.
What two molecules in Figure 2.1 might be called complex carbohydrates? _________ and _________.
What is your evidence?
5.
What is the same about the two types of molecules?
6.
What is different?
In the 19th century, chemists analyzed a variety of inedible plant materials like sawdust, cotton, and linens and
found that they, too, were made up of hundreds and thousands of glucose molecules linked together by
chemical bonds. A French chemist gave these long chains of glucose the name of cellulose. Scientists later
discovered that the bonds holding the glucose molecules together in cellulose were different than the bonds
holding the glucose molecules together in starch. Because cellulose is made up of long chains of glucose, it too
is considered a complex carbohydrate. Nutritionists sometimes simply refer to cellulose as fiber.
The complex carbohydrate with the curve bars linking the glucose molecules is how we represent cellulose in
Figure 2-1. The curved bars are used to show that glucose molecules are bonded differently in cellulose than in
starch.
7.
What molecule in Figure 2-1 represents cellulose? Number _________
Proteins are another major component of food. They are composed of smaller subunits called amino acids.
Unlike complex carbohydrates, which are made up thousands of only one type of sugar (glucose) linked
together, proteins are made up of hundreds of several different types of amino acids. There are actually
twenty different types of amino acids.
8.
9.
Which molecules in Figure 2-1 do you think represents proteins? Numbers _________ and _________.
What is your evidence?
The final major components of food that have been recognized since early times are fats and oils. Fats and oils
are greasy feeling and do not mix well with water. Today scientists realize that fats and oils are chemically very
similar. Fats are solid at room temperature whereas oils are liquid at room temperature.
Scientists have also found that unlike complex carbohydrates and proteins, fats and oils are medium sized
molecules made up of four smaller subunits. Three of the four small molecules are almost identical and are
called fatty acids. These three molecules are each linked to the fourth molecule called glycerol.
10.
Which molecules in Figure 2-1 represent fats or oils? Numbers _________, _________, _________ and _________.
Table 2-3: Scientist’s Groupings- Summarize what you just did by placing the molecules into the four groups
the same way the scientist did:
Group Name
Molecules in Group
(List by number)
Why did the scientist place these molecules together?
Scientists have found that over ninety-five percent of almost all foods are composed of carbohydrates, proteins,
and fats.
11.
How does the scientist’s grouping of food molecules compare to the grouping of food molecules that you
suggested in your initial ideas? Explain.
PART 2: NUTRIENTS IN FOOD. Now let’s look at some advantages of grouping food into carbohydrates,
proteins, and fats. In fact, almost all packaged food comes with labels that inform you how much protein,
carbohydrates, and fats are in a particular food. In the following exercise you will learn how to determine the
relative amounts of protein, carbohydrates, and fat in a particular food from its label.
Google a picture of a nutrition label for any food (make sure it has carbs, proteins and fats in it, and that the
serving size is in grams). It should tell you how many total grams of carbohydrates, proteins and fats in a
particular serving of that food. Put this information in the table below in the weight column.
If the weights of the carbohydrates, proteins and fats are known, then it is relatively easy to express these
weights as a percentage. For example, if the total weight of the serving size is 20g and the weight of
carbohydrate in the serving size is 5g then the % carbohydrate would be determined as follows:
(Weight of carbohydrate (g) / total wt. of serving size (g)) *100 = % carbohydrate
or
(5g carbohydrate / 20g total wt. of serving size) *100 = 25%
Table 2-4: Nutrition Label
Nutrient
WEIGHT PER SERVING
(grams)
TOTAL SERVING SIZE
(grams)
PERCENT IN 1 SERVING
(%)
Carbohydrate
Protein
Fat
*NOTE: Don’t use the percent calculated on the “Nutritional Facts” label; that percentage is based on daily
requirements.
Summarizing Questions
12. All our food consists primarily of what three molecules (excluding water)?
13.
Excluding water and such things as shells and bones, all organisms are primarily made up of what three
molecules (HINT: why do you think I would ask you this question after asking you the previous
question)?
How do animals use food to grow? In this activity, we explore more deeply the relationship between the food
that we eat and the composition of our bodies.
Initial Ideas
14. How do you think organisms use the food that they eat to grow (become larger in size)? In other words,
what does our body do with that food?
Refer back to Figure 2-1. The molecules represented in that Figure are the carbohydrates, proteins and fats
that might be found in a pizza with all the works. As previously pointed out, Figure 2-1 might represent these
molecules just after they entered your mouth after taking a big bite of the pizza.
Changes to Molecules over Time
Scientists have procedures to chemically “label” molecules so they can be traced. Imagine that before the food
molecules on the diagrams were consumed by the person, they were “labeled” so that they could be followed
through the digestion process. At four different time intervals, samples were taken from different places in the
body. Use the Data for Nutrients Packet in elearning to complete this section. The data for the different
time intervals were recorded and illustrated in the Time 0 through Time 4 diagrams. Observe the changes in
location and appearance of the molecules of food for each time interval. Record your observations in the table
below.
Table 2-5: Progression of Digestion
Time Interval
Observations
Time 0-Time 1
Time 1-Time 2
Time 2-Time 3
Time 3-Time 4
Count all the subunits (smaller pieces) individually that are part of the large molecules originally
present in the mouth at Time 0. Even if it is connected to others, you should still include it. Record your
results in the table below.
16. Count all the subunits at Time 4 in the blood, the typical cell, and the fat cell whether they are ‘free’ or
connected together to form larger molecules, and put your results in the table below.
15.
Table 2-6: Subunits (pieces)
Group
Number of Subunits at Time 0
*Did you account for all the building blocks? COUNT EVERYTHING!
Number of Subunits at Time 4
17.
Summarize what happened to the molecules that originally entered the mouth over the time period
between Time 0 and Time 4.
Reassembly- The breakdown of larger molecules into subunits also helps the reassembly of new molecules,
which are needed for growth, and maintenance of organisms’ bodies. Sometimes the main function of these
reassembled carbohydrates, proteins and fats is to make the structure of the organism. Other times these
newly assembled molecules serve mainly as storage materials for later use within the organism. When plants
need more structure they assemble sugar molecules to make cellulose. However when they simply want to
store carbohydrates, they assemble the glucose subunits into starch. We will learn more about this when we
get into photosynthesis.
Animals rarely build their structure out of carbohydrates. They typically will just use amino acids to build
proteins which will code for traits and functions within the animal’s body. These proteins can also become
parts of muscle. Animals do, however, store sugar molecules in long chains like plants do. This long chained
molecule is composed of subunits very similar to starch, but it is called glycogen. We have not mentioned
glycogen previously because it is only a minor component of food. Though we store glycogen, it never makes
up more than about 1.5% of our total body weight. Most glucose is converted into lipids that are stored within
our bodies for later use. This is typical for almost all animals. When our bodies reassemble the components
from fats, they also return to their original form of fats stored in our bodies for later use.
Fill out the following table. You will want to refer to the Scientists’ Ideas in part 1 of the packet and the
section above that explains the reassembly.
Molecule(s) by What are these
number in
molecules called?
Figure 2-1
What are these molecules broken down
into when we digest them (subunits
from part 1)?
When these molecules
are reassembled within
our cells, what are they
reassembled into?
Digestion and Growth
In the diagrams, you observed that the larger molecules were broken down into subunits before being
reassembled in cells. This breakdown facilitates two processes: distribution and reassembly.
Distribution- In order for food molecules to pass from the small intestine to the blood vessels, the food must
first pass through the cells that line both the small intestine and blood vessels. The digestive process that goes
on in the stomach and small intestine helps this transfer by making the molecules small enough to pass more
easily into and out of cells.
Cellulose (molecule #3) behaves differently than the other molecules. Cellulose is a major part of plant cell
walls that can’t be digested by most animals. What this shows is that not all carbon sources can be used for
food. Approximately 50% of our waste (feces) consists of cellulose and other indigestible food products and
50% consists of dead bacteria, which once lived in the digestive tract. Scientists have shown that some
microorganisms that live outside our bodies can ‘digest’ cellulose.
18.
When these microorganisms digest cellulose, what subunits would they be able to break cellulose into?
19.
Explain your reasoning.
Summarizing Questions
20. Describe how the glucose subunits that compose starch (in say spaghetti) can end up as part of glycogen
in one of your cells.
21.
What happens to cellulose in our digestive tract?
22.
What happens to a fat molecule in our digestive tract?
23.
What typically happens to amino acids once they arrive in a cell?
24.
What are the three major food molecules recognized by scientists?
25.
How are these molecules similar to each other?
26.
How do these molecules differ from each other?
27.
What are the two major subdivisions of carbohydrates?
28.
How are the two major subdivisions different?
29.
How are cellulose and starch similar?
30.
How do cellulose and starch differ?