Human body consists of Inorganic and Organic compounds

The human body is made up of atoms, ions and molecules.  Life processes depend on the organization and interaction of these chemical units.  An atom is the smallest amount of the chemical element that has the characteristic properties of that element.  An ion is an electrically charged atom or a group of atoms.  For example electrically charged hydrogen atom is also called hydrogen ion.  Because of their electric charges, ions are very important in many life processes including energy transformation, transmission of nerve impulses and muscle contraction.

A chemical compound is a molecule that consists of two or more than two different atoms combined in a fixed proportion.  For example water is a chemical compound consisting of two atoms of hydrogen chemically combined with one atom of oxygen.

Chemical compounds can be classified into two broad groups, organic and inorganic compounds.  Inorganic compounds are relatively simple, small compounds such as water, salt, simple acid like hydrochloric acid, and simple base like ammonia.  These substances are required for fluid balance and for many activities of cell such as transporting materials through the cell membrane.  Organic compounds are large, complex compounds containing carbon.  These are the chemical building blocks of the body and also serve as fuel molecules that provide energy for body activities.  Organic compounds also regulate and participate in thousands of chemical reactions necessary for life.

Four important group of organic compounds are carbohydrates,  lipids, proteins, and nucleic acid.

• Carbohydrates are sugars and starches.  They are used as fuel by the body and to store energy.  Glucose is a simple sugar that is a main source of energy for the body.  The liver and muscles can link glucose molecule into long chains, producing glycogen, a large molecule that can be stored.
• Lipids include fats, compounds that store energy; phospholipids, which are components of cell membrane; and steroids, which include several hormones.
• Proteins are complex, and large compounds composed of subunits called amino acids.  Some proteins serve as enzymes, catalyst that regulate chemical reactions.  Other proteins are the structural components of cells and tissues.  The kind and amount of proteins in a cell determine to a large extent what a cell looks like and how it functions.  For example, muscle cells have large amounts of the proteins myosin and actin, which are responsible for their appearance and their ability to work.  
• Nucleic acid are also large and complex compounds.  Two very important nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) .  DNA makes up genes (the hereditary material) .  It contains the instructions for making all the proteins needed by the cell.  RNA is important in the process of manufacturing proteins.

Levels of organization within the human body

The body is highly organized.The simplest level of organization is the chemical level,consisting of atoms and molecules.All matter is composed of chemical elements -pure chemical substances like iron,calcium or oxygen.About 98% of the human body is composed of 6 elements-oxygen,carbon,hydrogen,nitrogen,calcium and phosphorus.An atom is the smallest amount of a chemical element that has the characteristic properties of that element.Atoms can combine chemically to form molecules.For example,two atoms of hydrogen chemically combine to form one molecule of water.

Atoms and molecules associate to form the organelles and cells(building block of the body)of the cellular level.The human body is composed of about 100 trillion cells of many types,such as bone cells,muscle cells and blood cells.Cells vary in size and shape according to their function,most of them are so small that they can be seen only with a microscope.Each cell consists of specialized cell parts called organelles.One organelle,nucleus,serves as the information and control centre of the cell.Several other kinds of organelles scattered throughout the cell perform specific functions like breaking down fuel molecules to provide energy and manufacturing needed substances.

Cells associate to form tissues such as muscle or bone tissue.A tissue is a group of closely associated cells specialized to perform particular functions.The four main types of tissues are muscle tissue,nervous tissue,epithelial tissue and connective tissue.

Tissues may be organized to form organs such as the brain or heart.The heart consists mainly of muscle tissue but it is covered by epithelial tissue and also contains connective and nervous tissue.

Certain tissues and organs function together to make up an organ system or a body system.For example,the circulatory system consists of the heart,blood vessels,blood,lymph structures and several other organs.

The body systems work together to make up the human organism.