.
Elements and Compounds In The Human Body
Chemical Composition of the
Human Body
Human Body Composition as Elements and Compounds
By Anne Marie Helmenstine, Ph.D.
Many of the elements found
throughout nature are also found within the body.
This is the chemical
composition of the average adult human body in terms of elements and also
compounds.
Major Classes of Compounds in the
Human Body
Most of the elements are found within compounds.
Water and minerals are
inorganic compounds.
Organic compounds include
fat, protein, carbohydrates, and nucleic acids.
· Water: Water is the most
abundant chemical compound in living human cells, accounting for 65 percent to
90 percent of each cell. It's also present between cells. For example,
blood and cerebrospinal fluid are mostly water.
· Fat: The percentage of fat varies
from person to person, but even an obese person has more water than fat.
· Protein: In a lean male, the
percentages of protein and water are comparable. It's about 16
percent by mass. Muscles, including the heart, contain a lot of muscle.
Hair and fingernails are protein. Skin contains a large amount of protein, too.
· Minerals: Minerals account for about 6
percent of the body. They include salts and metals. Common minerals
include sodium, chlorine, calcium, potassium, and iron.
· Carbohydrates: Although humans use the sugar
glucose as an energy source, there isn't that much of it free in the
bloodstream at any given time. Sugar and other carbohydrates only account
for about 1% of body mass.
.
Elements in the Human Body
Six elements account for 99% of the mass of the human
body.
The acronym CHNOPS may be
used to help remember the six key chemical elements that are used in biological
molecules.
C is carbon, H is hydrogen, N is nitrogen, O is oxygen, P is
phosphorus, and S is sulfur.
While
the acronym is a good way to remember the identities of the elements, it
doesn't reflect their abundance.
· Oxygen is the most abundant
element in the human body accounting for approximately 65% of a person's mass.
Each water molecule consists of two hydrogen atoms bonded to one oxygen
atom, but the mass of each oxygen atom is much higher than the combined mass of
the hydrogen. In addition to being a component of water, oxygen is essential
for cellular respiration.
· Carbon is contained in all
organic compounds, which is why carbon is the second most abundant element in
the body, accounting for about 18% of body mass. Carbon is found in proteins,
carbohydrates, lipids, and nucleic acids. It's also found in carbon dioxide.
· Hydrogen atoms are the most
numerous type of atom in a human, but because they are so light, they only make
up around 10% of the mass. Hydrogen is in water, plus it's an important
electron carrier.
· Nitrogen is about 3.3% of body
mass. It's found in proteins and nucleic acids.
· Calcium accounts for 1.5% of body
mass. It's used to build bones and teeth, plus it's important for muscle
contraction.
· Phosphorus is about 1% of body mass.
This element is found in nucleic acids. Breaking bonds connecting phosphate
molecules is a major component of energy transfer.
· Potassium is around 0.2-0.4% of the
mass of a person. It's used in nerve conduction. Potassium is a key cation or
positively-charged ion in the body.
· Sulfur is found in some amino
acids and proteins. It's about 0.2-0.3% of body mass.
· Sodium, like potassium, is a
positively-charged ion. It's about 0.1-0.2% of body mass. Sodium helps regulate
the electrolyte balance in the body and maintain homeostasis with respect to
the volume of water in the blood and cells.
· Although aluminum and silicon are
abundant in the earth's crust, they are found in trace amounts in the human
body.
· Other trace elements include
metals, which are often cofactors for enzymes. Trace elements include iron,
cobalt, zinc, iodine, selenium, and flourine.
Element
|
Percent by
Mass
|
Oxygen
|
65
|
Carbon
|
18
|
Hydrogen
|
10
|
Nitrogen
|
3
|
Calcium
|
1.5
|
Phosphorus
|
1.2
|
Potassium
|
0.2
|
Sulfur
|
0.2
|
Chlorine
|
0.2
|
Sodium
|
0.1
|
Magnesium
|
0.05
|
Iron, Cobalt,
Copper, Zinc, Iodine
|
trace
|
Selenium,
Fluorine
|
minute
amounts
|
Reference: Chang, Raymond
(2007). Chemistry, Ninth Edition. McGraw-Hill. pp. 52.
No comments:
Post a Comment