뒤로Basic Chemistry for Biology: Atoms, Elements, and Water
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Chapter 2: Basic Chemistry
Introduction to Chemistry in Biology
Chemistry forms the foundation of biological processes. Understanding atoms, elements, and molecules is essential for studying life at the molecular level.
Atoms are the basic units of matter, composed of subatomic particles.
Elements are pure substances consisting of only one type of atom.
Molecules are formed when atoms bond together.
Elements Essential to Life
Living organisms are composed of a limited number of elements, with a few making up the majority of biological mass.
Major elements in living organisms: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S), Calcium (Ca), Potassium (K), Sodium (Na), Chlorine (Cl), Magnesium (Mg), Iron (Fe).
Trace elements are required in small amounts but are vital for biological functions.
Example: Figure 2.1 compares the abundance of elements in Earth's crust versus living organisms, showing that elements like carbon and nitrogen are much more prevalent in life than in the crust.
Structure of the Atom
An atom consists of a nucleus containing protons and neutrons, surrounded by electrons in shells.
Proton: Positively charged particle in the nucleus.
Neutron: Neutral particle in the nucleus.
Electron: Negatively charged particle in electron shells around the nucleus.
Particle | Electric Charge | Atomic Mass Unit (AMU) | Location |
|---|---|---|---|
Proton | +1 | 1 | Nucleus |
Neutron | 0 | 1 | Nucleus |
Electron | -1 | 0 | Electron shell |
Atomic Number and Mass Number
Atoms are identified by their atomic number and mass number, which are shown in chemical notation.
Atomic number (Z): Number of protons in the nucleus; determines the element.
Mass number (A): Total number of protons and neutrons.
Atomic symbol: One or two-letter abbreviation for the element.
Example: For carbon: Atomic number: 6 Mass number: 12 Symbol: C
Water: Structure and Properties
Water is a vital molecule for life, with unique properties due to its molecular structure.
Polarity: Water is a polar molecule; oxygen is partially negative (), hydrogens are partially positive ().
Hydrogen bonds: The polarity of water allows it to form hydrogen bonds, leading to cohesion and adhesion.
Solvent properties: Water dissolves ionic compounds and many polar molecules.
Acids, Bases, and pH
The pH scale measures the concentration of hydrogen ions in a solution, indicating its acidity or basicity.
Acid: Substance that increases hydrogen ion concentration (); pH < 7.
Base: Substance that decreases hydrogen ion concentration; pH > 7.
Neutral: Pure water has a pH of 7.
pH Value | Examples |
|---|---|
1-2 | Stomach acid, lemon juice |
3-4 | Vinegar, cola, beer |
5-6 | Tomatoes, black coffee, wine |
7 | Pure water |
8-9 | Baking soda, Great Salt Lake |
10-11 | Household ammonia |
12-13 | Household bleach, sodium hydroxide |
Key Equations
Atomic mass calculation: where = mass number, = atomic number (protons), = number of neutrons.
pH calculation:
Summary
Understanding the basic chemistry of atoms, elements, and water is essential for studying biological systems. The unique properties of water and the role of elements in life are foundational concepts in biology.
Additional info: Some content and examples were inferred from standard biology curriculum to ensure completeness and clarity.
