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Name:_________________
Date:___________________
The Chemistry of Life
Living things are made up of matter. Matter is anything that has mass and takes
up space. Matter is made of tiny particles called atoms. Atoms make up
elements. An element is a substance that is made up of only one kind of atom.
Oxygen and hydrogen are examples of elements. Matter is often made up of
two or more different elements joined together to form a compound.
Scientist use a certain symbol for each different element to save
themselves (and you, too) time writing out really long names. When written
together, the symbols make up a chemical formula. A chemical formula is a
way to write the name of the compound using symbols. The symbol for oxygen
is O. The symbol for hydrogen is H. In the chemical formula for water (H2O) the
small two means there are 2 hydrogen atoms in the molecule. Sometimes the
symbols are more than one letter. If this happens, the first letter is always
capitalized and the second letter is always lower case.
Six elements make up over 97% of matter in living things. Those six
elements are carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. The
percentage of these 6 elements in living things is shown in the pie graph below.
Elements % of living things
3%
0.30%
1.40%
3%
oxygen
10%
carbon
hydrogen
nitrogen
phosphorus
18%
65%
sulfur
trace elements
These six elements make up the important substances needed for all living
things. The substances that are important to life are sometimes called
macromolecules. They can be very, very big molecules. They fall into four
groups: carbohydrates, proteins, lipids, and nucleic acids.
A carbohydrate is made of carbon, hydrogen, and oxygen. No other
types of atoms can be found in a carbohydrate. Carbohydrates are made of
little molecules called monosaccharides. Monosaccharide is a fancy word
meaning one (mono) sugar (saccharides). Examples of monosaccharides are
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glucose (blood sugar) and fructose (fruit sugar). If you hook two
monosaccharides together you get a disaccharide
(di- means two, duh). An examples of a disaccharide
is sucrose (table sugar) made up of glucose and
fructose. If you hook lots of monosaccharides
together you get a polysaccharide. Examples of
polysaccharides are starch and cellulose found in
plants as well as glycogen found in animals.
Okay, enough with the fancy names, what do
they do for you? They are great for quick energy.
What do long distance runners do the night before the
big race? They eat a big plate of spaghetti. That’s
called carb loading and will supply them with the
energy they will need to run the next day. So
carbohydrates are quick energy.
Proteins are also important substances for life. Proteins are made out of
carbon, hydrogen, oxygen, nitrogen and usually
sulfur. These huge molecules are made up of
smaller molecules called amino acids. Proteins are
used for two different things in you body. They can
be used as structural things like muscle and bone.
They can also be used for functional things called
enzymes and hormones. Enzymes have a very
important job in living things. They help a chemical
reaction to happen but are not changed by the
reaction. Enzymes help the reaction to occur at lower, safer temperature so
you will not die. Hormones are chemicals made by your body to regulate the
processes in your body. An example of a protein hormone is insulin. It acts like
a gatekeeper for glucose to enter your cells.
Lipids are commonly known as fats and oils. Lipids are
made up of carbon, hydrogen and oxygen. Some
examples of lipids are butter, corn oil, candle wax, and
animal fat. All lipids do not like water. Lipids are huge
molecules made of fatty acids. Lipids are really good at
storing energy for long-term use. Some hormones are also
lipids as well. Examples of a lipid hormones are
testosterone and estrogen. Both of these hormones are
important for the health of your reproductive organs.
The last group of macromolecules is called nucleic
acids. They are made out of carbon, hydrogen, oxygen,
nitrogen and phosphorus. These atoms are arranged into
molecules called nucleotides. Nucleic acids have a very
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important job in the cell. They are responsible for keeping all the information
needed to run the cell. The type of nucleic acid that does this is called
deoxyribonucleic acid or DNA for short. DNA is usually found in the nucleus of a
cell. Another type of nucleic acid is ribonucleic acid or RNA for short. It’s a
messenger from the nucleus of a cell to the protein factories outside the
nucleus.
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Name:_________________
Date:___________________
The Chemistry of Life Review
1. What is an example of a lipid?
2. What are carbohydrates used for in your body?
3. What elements make up proteins?
4. What is an example of a nucleic acid?
5. What give two examples of a disaccharide.
a.
b.
6. What is the function of a lipid?
7. What are two things proteins are used for in your body?
a.
b.
Fill in the following table dealing with carbohydrate molecules
Number of
Name of Carbohydrate
Saccharides
Example
type
(sugars) in it
1
8.
10.
12.
9.
Sucrose (table sugar)
11.
many
13.
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Compounds in Living Organisms
The compounds your body needs for energy and building materials are
carbohydrates, proteins, fats, vitamins, and other nutrients. These compounds are
present in the plants and animals you use as food.
Purpose: In this investigation, you will do tests for compounds and then use those tests
to figure out which compounds are found in ordinary foods.
Materials: test tubes, droppers, beaker of hot water, hot plate, benedict’s solution,
biuret solution, brown paper bag, gelatin solution, glucose (sugar) solution, Lugol’s
iodine, starch solution, salt (NaCl) solution, AgNO3 (silver nitrate) solution, butter,
mayonnaise, orange juice, whole milk, egg white solution, Enfamil (baby formula),
liver, apple sauce, potato, other food
Prediction: See data table to make your hypotheses.
Procedure:
Caution: The chemicals you will use in this procedure may be corrosive, poisonous,
and or irritants, and they may destroy clothing. Avoid skin and eye contact; do not
taste anything. Should a splash or a spill occur, call you teacher immediately. If any
gets in your eye, wash with water for 15 minutes. If chemicals get on your hands, wash
them immediately.
Note: The full lab ensemble (safety glasses and apron) will be worn while testing your
Your teacher will not remind you, if you remove your
safety glasses without permission, you will not finish the lab and
will get a zero.
substances.
Part A : Reagent Tests for Known Substances
Scientist use special chemical solutions (reagents) to find out if certain compounds
are present. To be able to test for these substances in food you need to know what
a positive test looks like. These tests are all made to show you a positive test.
Describe the results in the data table for known substances.
How to do the tests
Protein test
Place 5 ml of the gelatin (protein) solution in a test tube. Record the color in the
data table. Add 10 drops of Biuret solution. Write what happens results in the data
table for known substances.
Glucose test
Add 20 drops of Benedict’s solution to 5 ml of the glucose test solution. Put your
mark on the label. Place the test tube in the beaker of boiling water that is on the hot
plate. Be careful not to burn yourself. Wait about 5 minutes. Remove the test tube
and record the results.
Caution: Use test-tube clamps to hold hot test tubes. Boiling water will scald, causing
second-degree burns. Do not touch the beaker or allow boiling water to contact your
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skin. Avoid vigorous boiling. Should a burn occur, call your teacher immediately.
Place burned area under cold running water.
Starch test
Add 5 drops of Lugol’s iodine solution to 5 ml of the starch test solution in a test
tube.
Chlorine Test
Put 5 ml of the NaCl solution in a test tube. Add 5 drops of silver nitrate. Describe
the results in the data table for known substances.
Fat test
Rub a small piece of butter on a piece of brown paper bag. Let it sit for a
couple of minutes then hold the paper up to the light. When food contains only a
small amount of fat, it may not be detected by this method.
Table 1 Positive Test Results
Food
Substance
Test Solution
Gelatin
(protein)
Biuret solution
Glucose
Benedict’s Solution
Starch
Lugol’s iodine solution
NaCl
Silver nitrate solution
Results
Before test
After test solution is
added
Butter
Brown Paper
(lipid)
Part B Testing Food
Using your assigned food, complete all of the following tests. Record your results as
either a + for present or a – for absent in the data table. Report the results for your
food on the overhead. Be sure to copy down the results for the other foods.
How to do the tests
Protein test
Place 5 ml of the food in a test tube. Add 10 drops of Biuret solution. Write a + if
the test is positive in the data table. Write a – if the test is negative in the data table.
Glucose test
Add 20 drops of Benedict’s solution to 5 ml of the food. Place the test tube in
the community beaker of boiling water that is on the hot plate. Be careful not to burn
yourself. Wait about 5 minutes. Remove the test tube and record the results.
Caution: Use test-tube clamps to hold hot test tubes. Boiling water will scald, causing
second-degree burns. Do not touch the beaker or allow boiling water to contact your
skin. Avoid vigorous boiling. Should a burn occur, call your teacher immediately.
Place burned area under cold running water.
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Starch test
Add 5 drops of Lugol’s iodine solution to 5 ml of your food in a test tube. Write +
or – in the data table.
Chlorine Test
Put 5 ml of your food in a test tube. Add 5 drops of silver nitrate. Write + or – in
the data table.
Fat test
Rub the food on a piece of brown paper bag. Hold the paper up to the light.
When food contains only a small amount of fat, it may not be detected by this
method. Write + or – in the data table.
NOTE : Wash Hand thoroughly before leaving the lab.
Table 2 Food Tests
Substance
Egg
Potato
Mayo
Liver
Whole
Milk
Enfamil
Orange
juice
Apple
Sauce
Protein
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Glucose
Starch
Chlorine
Lipid
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Discussion questions:
1. Based on your hypotheses, were you surprised by any of the results? Explain.
2. Which, if any, of the foods contained all of the compounds you tested (If none
contained them all, which food had the most compounds)?
3. Based on your tests, which foods could be used as a source of:
4.
a. Protein?
b. Glucose?
c. Starch?
d. Fat?
5a. Did the color of the test food make it hard to see positive results?
b. Which foods, if any, did the color of the test food make it hard to see positive
result?
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Analysis of Compounds in Common Foods
Substance
Egg
Potato
Mayo
Liver
Whole
Milk
Enfamil
Orange
juice
Apple
Sauce
Protein
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Prediction
Test
results
Glucose
Starch
Chlorine
Lipid
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Analysis of Compounds in Common Foods
Substanc
e
Egg
Protein Glucose Starch
Test
results
Potato
Test
results
Mayo
Test
results
Liver
Whole
Milk
Test
results
Test
results
Enfamil
Test
results
Orange
juice
Test
results
Apple
Sauce
Test
results
Vit. C
Cl-
Lipid