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Chapter 2: Essential Chemistry for Biology

Basic Concepts in Chemistry

• Matter:

  • Defined as anything that occupies space and has mass.

  • Exists in three states: solid, liquid, and gas.

  • Composed of elements (substances that cannot be broken down into other substances).

Elements of Life

• Elements represented in biological systems:

  • Essential Elements:

    • Major Elements (96% of most cells):

      • Oxygen (O): 65.0%

      • Carbon (C): 18.5%

      • Hydrogen (H): 9.5%

      • Nitrogen (N): 3.3%

    • Minor Elements: Calcium (Ca), Magnesium (Mg), Chlorine (Cl), Sodium (Na), Sulfur (S), Potassium (K), Phosphorus (P).

  • Trace Elements: Required in very small amounts (e.g., Iron (Fe), Iodine (I), Copper (Cu), etc.).

Atoms

• Fundamental building blocks of elements.

• Each element consists of one kind of atom, the smallest unit of matter that retains chemical properties.

Subatomic Particles

• An atom consists of:

  • Protons: Positively charged particles found in the nucleus.

  • Neutrons: Electrically neutral particles found in the nucleus.

  • Electrons: Negatively charged particles found in the electron cloud surrounding the nucleus.

Atomic Structure

• Atomic Number:

  • Number of protons in an atom, which defines the element.

• Mass Number:

  • Sum of protons and neutrons in the nucleus.

  • Electrons are negligible in mass.

  • Example: Carbon atom has atomic number 6 and mass number 12.

Isotopes

• Definition:

  • Different mass forms of an element with the same number of protons/electrons but different neutrons.

• Radioactive Isotopes:

  • Unstable nucleus that decays and emits radiation.

  • Applications: Carbon dating and medical imaging.

Electron Configuration

• Electron Shells:

  • Energy levels within the electron cloud.

  • Outer shell elections dictate chemical behavior; atoms strive for a full outer shell to be stable.

Chemical Bonds

• Ionic Bonds:

  • Formed by the transfer of electrons between atoms, resulting in charged ions (NaCl example).

• Covalent Bonds:

  • Formed by the sharing of electrons between two atoms.

  • Types include nonpolar (equal sharing) and polar (unequal sharing, e.g., H2O).

Hydrogen Bonds

• Result from the polarity of molecules, leading to weak attractions between water molecules.

  • Crucial for the unique properties of water like cohesion and high surface tension.

Properties of Water

• Hydrogen Bonding:

  • Provides water with life-supporting properties.

  • Cohesion: water molecules stick together.

  • High surface tension facilitates transport in plants.

• Temperature Regulation:

  • Water's ability to absorb and store heat leads to stable temperatures in organisms.

Ice and Density

• Ice less dense than liquid water, allowing it to float, which is crucial for aquatic life.

Water as a Solvent

• Water can dissolve a variety of substances, essential for biochemical reactions.

Acids, Bases, and pH

• Acids: Release H+ ions in solutions.

• Bases: Accept H+ ions (release OH- instead).

• Buffers: Substances that resist pH changes by adjusting H+ ion concentrations (e.g., maintains human blood pH around 7.4).

Summary

• Understanding basic chemistry is fundamental for studying biology and the interactions of elements, compounds, and biological molecules.