General biology unit 2

Biology and the Principles of Chemistry and Physics

This chapter reviews essential chemistry concepts as they apply to living organisms, providing foundational knowledge for General Biology students.

Concept 2.1: Emergent Properties and Elements of Life

Understanding the basic chemical principles is crucial for studying biological systems. This section introduces key terms and the elements essential for life.

• Matter: Anything that occupies space and has mass.

• Element: A substance that cannot be broken down into simpler substances by chemical means.

• Compound: A substance formed when two or more elements are chemically bonded together.

• Emergent Properties: New characteristics that arise when individual components interact within a system.

• Elements of Life: The four most abundant elements in living organisms are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).

• Additional Important Elements: Phosphorus (P), sulfur (S), calcium (Ca), potassium (K), and sodium (Na) are also vital for biological functions.

• Common Trace Elements: Elements required in minute amounts, such as iron (Fe) and iodine (I).

Example: Water (H2O) is a compound with emergent properties such as cohesion and temperature moderation, which are not present in its individual elements.

Concept 2.2: Atomic Structure and Isotopes

Atoms are the basic units of matter, and their structure determines the properties of elements and compounds. This section covers atomic components and isotopes.

• Atom: The smallest unit of an element, retaining its chemical properties.

• Subatomic Particles:

  • Proton: Positively charged particle in the nucleus.

  • Neutron: Neutral particle in the nucleus.

  • Electron: Negatively charged particle orbiting the nucleus.

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

• Isotope: Atoms of the same element with different numbers of neutrons.

  • Radioactive Isotope: An isotope with an unstable nucleus that decays over time, emitting radiation.

• Electron Shells and Orbitals: Electrons are arranged in shells around the nucleus; orbitals are regions where electrons are likely to be found.

• Periodic Table: Organizes elements by atomic number and properties.

• Biological Relevance of Isotopes: Used in medical imaging and dating fossils (e.g., carbon-14 dating).

Example: Carbon-12 and carbon-14 are isotopes of carbon; carbon-14 is used in radiometric dating.

Equation: $\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$

Concept 2.3: Chemical Bonds and Molecular Interactions

Chemical bonds hold atoms together in molecules and compounds, determining their structure and function in biological systems.

• Chemical Bond: The force holding two atoms together in a molecule.

• Covalent Bond: Atoms share electrons; can be single, double, or triple bonds.

• Ionic Bond: Atoms transfer electrons, resulting in oppositely charged ions that attract each other.

• Electronegativity: The ability of an atom to attract electrons in a bond.

• Polar Covalent Bond: Unequal sharing of electrons, leading to partial charges.

• Nonpolar Covalent Bond: Equal sharing of electrons.

• Bond Strength: Covalent bonds are generally stronger than ionic bonds in biological systems.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

• van der Waals Interactions: Weak attractions due to transient local charges.

• Molecular Shape: Determined by the arrangement of atoms and bonds; crucial for biological function (e.g., opiates and endorphins).

Example: Water molecules are held together by hydrogen bonds, giving water its unique properties.

Equation: $\text{Electronegativity Difference} = |\text{Electronegativity}_A - \text{Electronegativity}_B|$

Concept 2.4: Chemical Reactions and Equilibrium

Chemical reactions transform substances by breaking and forming bonds. Understanding reactants, products, and equilibrium is essential in biology.

• Chemical Reaction: Process in which substances (reactants) are transformed into new substances (products).

• Reactant: Starting material in a chemical reaction.

• Product: Substance formed as a result of a chemical reaction.

• Reversible Reaction: Reaction that can proceed in both directions.

• Chemical Equilibrium: State in which the forward and reverse reactions occur at the same rate.

  • Example: Photosynthesis and cellular respiration are biological processes involving chemical reactions and equilibrium.

• Conservation of Matter: Matter cannot be created or destroyed in a chemical reaction (Law of Conservation of Mass).

Equation: $\text{Reactants} \rightleftharpoons \text{Products}$

Example: In photosynthesis, carbon dioxide and water are converted into glucose and oxygen.

Table: Types of Chemical Bonds and Their Properties

Bond Type	Definition	Relative Strength	Biological Example
Covalent	Atoms share electrons	Strong	Water (H2O), DNA backbone
Ionic	Atoms transfer electrons	Moderate	NaCl (table salt)
Hydrogen	Attraction between H and electronegative atom	Weak	Between water molecules
van der Waals	Transient local charges	Very Weak	Interactions between lipid molecules

Additional info: Academic context and examples have been expanded for clarity and completeness.