Chemical Basis of Life

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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 elements are Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N). These make up about 96% of the living matter in your body. Calcium (CA), Phosphorus (P), Potassium (K), sulfur (S), and a few other elements account for most of the remaining 4%. Trace Elements: elements that make up less that 0.01 percent of your body mass are nevertheless critical to your health.

Compounds

•Most elements can interact with other elements forming complex types of matter called compounds. Compound: A substance containing two or more elements that are chemically combined in a fixed ratio. •Compounds properties may differ greatly from those of its components. •Though simple compounds like sodium chloride and water play important roles in living things, most compounds found in organisms are more complex, containing at least three or four elements.

Concept 4.2
Chemical properties are based on the structure of atoms.

•Different elements have different properties.
•Some are solid metal at room temperature, some are invisible gases, some elements readily react with other elements, whiles others hardly react at all. •These properties affect the roles that different elements play in biological processes. This section...
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