The Chemical Context of Life (Campbell Biology, Chapter 2) - Study Notes

Chapter 2: The Chemical Context of Life

Introduction

This chapter explores the fundamental chemical principles that underlie biological processes. Understanding the chemical context of life is essential for studying how living organisms function at the molecular level.

Concept 2.1: Matter Consists of Chemical Elements in Pure Form and in Combinations Called Compounds

Definition of Matter

• Matter is anything that takes up space and has mass.

• All organisms are composed of matter.

Elements and Compounds

• An element is a substance that cannot be broken down to other substances by chemical reactions.

• A compound is a substance consisting of two or more elements in a fixed ratio.

• Compounds have characteristics (emergent properties) different from those of their constituent elements.

Example: Formic Acid

• Formic acid (found in ant venom) is a compound made of carbon, oxygen, and hydrogen atoms joined by bonds.

• The properties of formic acid depend on the types of atoms present and how they are bonded together.

Atoms and Their Properties

• The number of protons in an atom determines its identity (atomic number).

• The electron distribution of an atom determines its ability to form bonds.

Key Table: Major Elements in the Human Body

Element	Symbol	Percentage of Body Mass (including water)
Oxygen	O	65.0%
Carbon	C	18.5%
Hydrogen	H	9.5%
Nitrogen	N	3.3%
Calcium	Ca	1.5%
Phosphorus	P	1.0%
Potassium	K	0.4%
Sulfur	S	0.3%
Sodium	Na	0.2%
Chlorine	Cl	0.2%
Magnesium	Mg	0.1%
Trace elements	-	<0.01%

Additional info: Trace elements include boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and zinc.

Essential and Trace Elements

• About 20-25% of the 92 natural elements are essential for life.

• Four elements—carbon, hydrogen, oxygen, and nitrogen—make up about 96% of living matter.

• Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur.

• Trace elements are required by organisms in minute quantities.

Adaptation to Toxic Elements

• Some elements can be toxic to organisms.

• Certain species can adapt to environments containing toxic elements (e.g., some plants adapted to serpentine soils).

Summary Table: Key Terms and Definitions

Term	Definition
Matter	Anything that takes up space and has mass
Element	A substance that cannot be broken down by chemical reactions
Compound	A substance consisting of two or more elements in a fixed ratio
Atom	The smallest unit of matter that retains the properties of an element
Trace Element	An element required by an organism in minute quantities

Example: Ants and Formic Acid

• Ants use formic acid as a defense mechanism against predators.

• The chemical properties of formic acid are determined by its molecular structure and the types of atoms involved.