CAMPELL BIOLOGY (12th edition)
Unit 1
The Chemistry Of Life
1. The Chemical Context of Life
Life is fundamentally chemical in nature. To understand biology, we must
first understand the chemical building blocks that make up organisms and the
interactions between them.
Essential Elements:
Of the 92 naturally occurring elements, only about 25 are essential for life.
Four elements—carbon (C), hydrogen (H), oxygen (O), and nitrogen
(N)—make up approximately 96% of living matter. Trace elements, such as
iron (Fe) and iodine (I), are required in minute amounts but are still vital.
, Atomic Structure:
Atoms, the smallest units of matter, are composed of:
Protons (positive charge) and neutrons (neutral) in the nucleus.
Electrons (negative charge) in orbitals around the nucleus.
Isotopes of an element differ in their neutron numbers, and some isotopes are
radioactive, useful for dating fossils or medical imaging
Unit 1
The Chemistry Of Life
1. The Chemical Context of Life
Life is fundamentally chemical in nature. To understand biology, we must
first understand the chemical building blocks that make up organisms and the
interactions between them.
Essential Elements:
Of the 92 naturally occurring elements, only about 25 are essential for life.
Four elements—carbon (C), hydrogen (H), oxygen (O), and nitrogen
(N)—make up approximately 96% of living matter. Trace elements, such as
iron (Fe) and iodine (I), are required in minute amounts but are still vital.
, Atomic Structure:
Atoms, the smallest units of matter, are composed of:
Protons (positive charge) and neutrons (neutral) in the nucleus.
Electrons (negative charge) in orbitals around the nucleus.
Isotopes of an element differ in their neutron numbers, and some isotopes are
radioactive, useful for dating fossils or medical imaging
