Elements of You!
Question: What are you made of?
Of the 92 naturally occurring elements, living things are composed of only 26. Out of
these 26 elements, 6 make up practically all of the weight of most living things. The other
20 elements essential for life are present in very small amounts, some in such tiny amounts
that they are designated simply as “trace” elements. The six most abundant elements are
listed below. After reading about the 6 elements, complete the chart to the right.
•
Carbon is familiar to almost everyone in the form of charcoal, which is nearly pure
carbon. Carbon can also form crystals such as graphite, which is used in pencil lead and
in lubricants, or as diamond, which few people would guess is also pure carbon. In living
organisms, carbon is combined with other elements to form carbohydrates, proteins,
fats, and other substances. Carbon comprises about 23% of the weight of a typical
animal and about 12% of the weight of a typical plant. That particular combination of
carbon, oxygen, and hydrogen shown below the carbon box is the simple sugar glucose. •
Hydrogen is a gas and it is the most abundant element in the universe. Most of the
hydrogen on earth is combined with other elements. Hydrogen gas is so light that it
easily escapes the Earth’s gravity at the upper edges of the atmosphere and is lost into
outer space. Plants and animals are about 10% hydrogen by weight. •
Nitrogen is a gas that makes up about 78% of the Earth’s atmosphere and is important
to living things as a component of genes and proteins. Nitrogen makes up about 3% of
an animal and 1% of a plant. •
Oxygen is also a gas, but it is 16 times as heavy as hydrogen, so it remains in the
atmosphere. Water is a combination of two atoms of hydrogen and one atom of oxygen.
Oxygen makes up about 61% of a typical animal and about 77% percent of a typical
plant. •
Phosphorus is not found in nature as a pure element, but only as phosphates. It is so
reactive that it will combine with almost anything it contacts, even air. Yet a certain
amount of it combined with other elements is necessary for life. Phosphorus makes up
about 1% of a plant or animal. •
Sulfur is a mineral found in rather high concentrations in our body tissues. About half
of the body’s total sulfur is concentrated in the muscles, while the other half is found
in the brain, hair, skin and bones. Sulfur comprises about 0.3% of our body weight.
Very few plants have significant amounts of sulfur, so it is not shown on the plant
diagram, but it makes about 0.3% of the weight of a mammal, such as a rabbit, because
it is one of the principle elements found in amino acids. % by weight is…
Color
Elements of You!
Element
Key
Plant
Animals
As you read the handout “Elements of You”,
black
Carbon (C)
summarize the percent of elements found in
yellow Hydrogen (H)
living things by completing the table. Then
blue
Nitrogen (N)
use the key to color the images below. The
red
Oxygen (O)
atoms rising and falling out of the boxes
green Phosphorus (P)
represent some of the compounds formed
orange Sulfur (S)
by these elements. Finally, fill in the
representative bands on the rabbit and bush as you read about the percentage (by weight)
of these living things formed by the six elements.
H2
C
C C
C
H C
H C
H O C
H C
H C
H C
H
O
O H
H
O H
O H
O
H
O2
N2
N2
O2
O2
H N O
H
N
N
H
H
O
N
N
H
P
O
O
H
H
C C N
O
H
H
O
H
Glycine
P
P
S
S
P
O
O P O
O
Phosphate
S
S
O H H
H O C C N H
H C H
H C H
S
H C H
H
Methionine
ose
Gluc
N2
H2
Water