Campbell+Biology+Concepts+and+Connections+9th+Ed

The Chemical Basis of Life

Introduction to Coral Reefs

• Coral reefs are diverse ecosystems formed from calcium carbonate skeletons of coral animals.

• They serve as habitats for a variety of marine life, including numerous fish species.

• Rising atmospheric CO2 is a threat to coral reefs due to its chemical reactions in seawater.

The Role of Chemistry in Life

• Chemistry is foundational to biology, explaining how elements combine into compounds.

• Chemical reactions are vital for cellular functions, emphasizing the importance of understanding chemistry in biological contexts.

Water: The Essence of Life

• Life originated in water, and all organisms depend on it for survival.

• Cells are composed of approximately 70% water, where essential chemical reactions take place.

• The distinct properties of water highlighted in this chapter are crucial for sustaining life.

Hierarchy of Biological Organization

• Biological systems are structured hierarchically, with new properties emerging at each level, starting from atoms to molecules and cells.

• Understanding the elementary chemical concepts is crucial as they apply throughout the study of life.

Chemical Bonds (Sections 2.5-2.9)

Structure of Atoms

• The atomic structure dictates the types of bonds possible between atoms.

• Living organisms consist primarily of certain elements, combined into compounds.

Elements and Compounds

• Elements: Substances that cannot be broken down into simpler substances (e.g., oxygen, carbon).

• Compounds: Composed of two or more different elements in a fixed ratio (e.g., sodium chloride).

• Pure substances can exhibit emergent properties that differ from their constituent elements.

Essential Elements for Life

• Humans require 25 essential elements, with 99% of body mass made up of six key elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

• Trace elements, while present in minor amounts, are crucial for various biological functions.

Trace Elements and Nutritional Health (Section 2.2-2.4)

Importance in Diet

• Trace elements such as iodine and iron are essential in very small quantities but crucial for health.

• Iodine deficiency can lead to health issues like goiter; sources include seafood and iodized salt.

• Iron deficiency is prevalent globally, especially among women and children; fortification and diet improvement are key solutions.

Public Health Measures

• Fluoride is added to drinking water for dental health, with a history of controversy demonstrating the intersection of science and public policy.

Atom Structure and Isotopes (Section 2.3-2.4)

Subatomic Particles

• Atoms consist of protons (+), neutrons (no charge), and electrons (-).

• Atomic number is defined by the number of protons, while mass number is the sum of protons and neutrons.

• Isotopes differ in neutrons but have the same atomic number, affecting stability.

Radioactive Isotopes

• Useful as tracers in biology and medicine; they help monitor processes within organisms despite posing some risks.

• Examples include studies on photosynthesis and medical imaging.

Chemical Bonds (Sections 2.5-2.8)

Types of Bonds

• The distribution of electrons affects chemical properties; atoms may interact to complete their outer electron shells through:

  • Ionic Bonds: Formed by electron transfer, creating charged ions that attract each other (e.g., NaCl).

  • Covalent Bonds: Involve sharing electrons, which can be polar (unequal sharing) or nonpolar (equal sharing).

• Hydrogen Bonds: Weaker interactions crucial for life, especially in water.

Water's Properties (Sections 2.10-2.14)

Cohesion and Surface Tension

• Cohesion among water molecules leads to surface tension, essential for water transport in plants.

Temperature Regulation

• Water's high heat capacity allows it to absorb heat, stabilizing environmental temperatures.

Ice's Density

• Ice's lower density compared to liquid water allows it to float, providing insulation for aquatic ecosystems.

Solvent Properties

• Water's polarity makes it an excellent solvent, facilitating numerous biological reactions necessary for life.

Acidic and Basic Conditions

• pH influences chemical reactivity; buffers in biological systems maintain stability within cells.

Impact of CO2 on Coral Reefs (Section 2.15)

Ocean Acidification

• Increasing atmospheric CO2 levels lower ocean pH, impacting marine life, particularly coral reefs through calcification processes.

• Studies show that diminished carbonate ion concentration slows coral growth, threatening ecosystem diversity.

Search for Extraterrestrial Life (Section 2.16)

Water as a Criterion

• The search for life on distant planets centers on detecting water, which is essential for life as demonstrated on Earth.