The most important chemical elements of the body are carbon, nitrogen, oxygen and hydrogen. There are others that are important also. Every element is made up of units called atoms, two or more atoms combine to a structure called molecule. Some are made of atoms of only one element and if they combine with another element compounds are formed. Water would be an example of this. Water is the most basic compound in the human body.
There are four other main compounds of the body carbohydrates, proteins, lipids, and nucleic acids. These compounds are complex structures containing an element of carbon. Each have a job in the body. The bodies carbohydrates provide energy for activities. Proteins perform several jobs such as building cells and important chemical functions. Lipids store extra fuel and as building material for cells. The nucleic acids carry instructions for the traits of the next generation.
A cell the basic unit of life can take in food, get rid of waste, and grow. In the human body there are trillions of cells. Cells are alive. The body replaces cells as they wear out or die. Cells have three main parts. The covering which is skin like called cell membrane. The inside cytoplasm resembles soft jelly. The nucleus inside the cytoplasm referred to as the control center of a cell.
The membrane lets some materials in and keeps others out. Food and oxygen are allowed through the membrane. Wastes are given off and carried away by the blood. Making up most of the cell the cytoplasm filled with organelles or organs of the cell. The mitochondrion is an organelle that changes food to energy so it can be used. The lysosome gets rid of waste.
The nucleus a solid ball in center of cells. The chromosomes the rod like structures are contained in the nucleus. There are 46 sets of chromosomes inherited half from mother and half from father.
Chromosomes are made up of genes. Genes carry the inherited characteristics of the parents. They carry the genetic code. This code is formed by a chemical substance called DNA. This is the master plan making all living things different.
Cells not only grow but they reproduce. New cells replace dead cells after they complete the growing process. Cells divide into two cells, two cells into four, four cells into eight so on and on. When a cell divides each daughter cell is exactly like the parent cell.
Cells get food from blood. They covert food to energy called energy metabolism. They also use some food to make new cell materials. Some cells store fat for later use.
The adult body has trillions of cells teeming with activity. They are all different. Yet share some traits like basic structure and characteristics parts. The cells are life’s building blocks. Many kinds of different cells make up the human body in different sizes and shapes. Each cell has a special form that makes it fit for the special job it has to perform.