Chemical Basis of Life Essay

790 Words Aug 29th, 2005 4 Pages
Chapter 4
The Chemical Basis of Life
Introduction
• Your body is an elaborate chemical system.
• Chemical signals between brain less enable your mind to understand what you see.
• You nourish those cells with chemicals that are obtained from food.
• Life is all about chemicals and how they interact

Concept 4.1

Life requires about 25 chemical elements

Elements

• Humans and other organisms are examples of matter.
Matter: Anything that occupies space and has mass. (Physical things)
• The various forms of matter are composed of one or more chemical elements.
Element: A pure substance that cannot be broken down into smaller substances by chemical means
• There are 25 elements are essential to life. Four of these
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• Atom- gets its name from the Greek word atomos, meaning "indivisible" is the smallest possible "Pierce"—it would take more than tree million carbon atoms to stretch across the period printed at the end of this sentence.
• Atoms are all elements are made up of even smaller components called subatomic particles.
Proton: Is a subatomic particle with a single unit of positive electrical charge.
Electron: is a subatomic particle with a unit of negative charge.
Neutron: is electrically neutral.
Nucleus: is the center of an atom. It is made up of tightly packed protons and neutrons.
• Electrons, which have much less mass than neutrons and protons continually, move about the outside of the nucleus at great speed.
• The attraction between the negatively charged electrons and the positively charged propones keeps the electrons close to the nucleus
• An important difference among elements is the number of protons in their atoms.
• All atoms of a particular element have the same number of protons known as the elements atomic number.
• Left alone, An atom tends to hold as many electrons as protons
• In that state, an atom is electrically neutral the positive charges on the protons exactly balance the negative charges. However, the numbers of electrons is not constant like the number of protons.
• The number of electrons determines how the atom interacts with other atoms. No two elements have the

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