Body Chemistry

1. Authors: Eliza Ivanova(age 15) and George
Velev(age 16)
Edited by A. Chidester

2. • Some scientists say that the human body is
“a walking periodic table”, since in contains
a variety of chemicals found in our
environment.
• Is this true? Let us find out!

3. Chemical compounds are generally divided into two categories.
In the first category are the inorganic compounds that are
composed of relatively small molecules bonded ionically.
In the second category fall the organic compounds that mainly
consist of carbon and hydrogen and build up the human body.
Certain salts (NaCl, CaCl), which are inorganic compounds,
exist in the human body as dissolved in water.

4. More than 62% of our body is water. The percentage depends
on the age of the human being- in children this percentage is
higher than in an adult’s body. Our daily consumption of water
is approximately 2.7 L. This amount of water may come from a
variety of sources: food, metabolism, drinking, and etc.
H2O regulates homeostasis and the body is not able to function
properly without it.

5. Any substance that releases hydrogen positive ions
(when it is dissolved in water) is called an acid.
Any substance that releases hydroxyl negative ions is
called a base.
An ionic substance that contains a negative ion other
than OH- or O2- is called a salt.
When acid reacts with base, the products are salt and
water. This process is called neutralization.

6. • The numerical scale that measures acidity or alkalinity is
called a pH scale. It has values ranging between 0 to 14.
• The pH of water is 7. It is considered to be neutral. Any
substance having a pH higher than 7 is considered to be
acidic and any substance having a pH lower than 7 is
considered to be basic.
• In order for homeostasis to be maintained in the human
body, body fluids (including blood) need to have a relatively
constant pH.

7. When a strong acid or base appears in the human
organism, it may be destructive for the human cells.
Substances called buffers (combinations of weak acids or
weak bases and their respective salts in a solution) help the
body fluids to resist changes in pH and to maintain the
balance in the organism.

8. Carbohydrates are the major source of energy for most
cells. They can be broken down in the cells in order energy
to be released.
Composition: carbon, hydrogen, and oxygen in a ratio
twice as much hydrogen as oxygen (example: CH2O, but
they can be more complex).

9. 1. Monosaccharides (comes from Greek) are the simplest type
of carbohydrates. They are the building blocks of more
complex sugars and cannot be broken down by hydrolysis.
2. Disaccharides (Di means 2) are the two monosaccharides
bounded together. They all have the same chemical formula
but differ in structure. (example: glucose, fructose).
3. The third type of carbohydrates are polysaccharides (poly
means many). Polysaccharide chains (called polymers) may
contain hundreds and thousands of monosaccharides. Their
general formula is (C6H10O5)n, n-the number of glucose
units in the molecule.

10. Fats are molecules that are rich in energy and are a source of
food reserve and long-term fuel.
They are stored in the organism in the form of neutral fats or
triglyceride.
Each fat molecule is composed of glycerol and fatty acids.
Two types of fatty acids exist:
- saturated fatty acids (solids at room temperature)
- unsaturated fatty acids – oils (liquid at room temperature)

11. These are fatty compounds containing alcohol, fatty acids,
and a phosphate group (PO43-), often linked with a
nitrogen containing group.
Fatty acid
Fatty acid
glycerol
phosphate alcohol
Every phospholipid has a hydrophilic head and non-
polar tails. This is important, for phospholipids build cell
membranes and they are all arranged with the water-
loving heads on one side and the tails- on the other.

12. These are fat-soluble compounds composed of four
bonded carbon rings, consisting of 17 carbons.
Examples: cholesterol, male and female sex hormones,
etc.)
Steroid hormones help regulate certain phases of
metabolism in the body such as puberty, menopause,
etc.

13. These organic compounds compose most of the tissues of the
body.
They contain carbon, hydrogen, oxygen, nitrogen (sometimes
sulfur), phosphorus, and iron.
Proteins form enzymes that control chemical activity (during the
break-down of food molecules in the stomach), protect us against
diseases in the form of antibodies, carry oxygen throughout the
body, make up some of the hormones, express genetic
information, and serve as indicators.
enzyme
A B A
B
enzyme
A+B

14. Amino acids are the basic building units of proteins.
They always contain an amino group (NH2) at one end of the
molecule and a carboxyl group at the other. An amino acid
contains one variable component. They may occur in
different chemical combinations. They simplest amino acid is
the glycine. It has only one hydrogen atom.
We know only 22 amino acids in the
living organisms. However, their
large variety of combinations can
create more than 50000 proteins in
the organism.

15. Nucleic acids are very large and complex molecules. They
carry the body’s hereditary messages and regulate the synthesis
of proteins.
The building blocks of NA are called nucleotides.
In 1869, the Swiss physician Friedrich Miescher first isolated
them from the nuclei of human pus cells.
There are two types of nucleic acids: deoxyribonucleic acid
(DNA) and ribonucleic acid (RNA).

16. •May be present in either the
nucleus or the cytoplasm
•actually, there are three types
- messenger R(mRNA) carries
genetic information from DNA
- transfer RNA (tRNA) is
involved in amino-acid
activation during protein
synthesis
- ribosomal RNA(rRNA) is
involved in ribosome structure.
•Makes up the chromosomes
within the cell’s nucleus
•holds the genetic code
•controls heredity
•Determines which proteins will
be synthesized in a cell and thus
controls the cell’s activity
RNA
DNA

17. • The energy that is produced from chemical
reactions in body is stored in a small
organic molecule called ATP(adenosine
triphosphate).
• When energy is needed, ATP is broken
down through hydrolysis and releases the
necessary energy.
ATP ADP(adenosine triphosphate) +
Pi(inorganic phosphate) + Energy

18. • Just before the end we would like to say that
this is not all that can be said about body
chemistry.
• No, we have just introduced you to the main
processes, but there are a lot more.
• If you are interested in any other ones, why
don’t you make a research for them by
yourself!

19. • “Body Chemistry.” Human Anatomy and
Physiology. 1990 ed.
• L’ organisme human. Le Petit Larousse en
Couleurs. 1996 ed.
• “Introduction to Body Chemistry.”
Chemistry in Brief. 1993 ed.
• Backgrounds created by Eliza Ivanova