Bio 211 Chapter 2 Questions and Answers

What are organisms composed of? Matter What is matter made up of? Elements What is an element? A substance that cannot be broken down to other substances by chemical reactions What is a compound? A substance that consists of two or more elements in a fixed ratio and it has characteristics different from those of its elements What are essential elements/what % are they of all elements? Elements that are essential to life and make up 20-25% of the 92 elements What 4 elements make up 96% of living matter? Carbon, hydrogen, oxygen, & nitrogen What 4 make up the other 4%? Calcium, phosphorus, potassium, & sulfur What are trace elements? Elements required by an organism in minute quantities What is an atom? The smallest unit of matter that still retains the properties of an element What are atoms composed of? Subatomic particles What are the 3 main types of subatomic particles & their charge? Neutrons= no charge Protons= + Electrons= - What is an atomic number? The number of protons in the nucleus of an element What is a mass number? The sum of protons plus neutrons in the nucleus of an element