General Biology: Elements, Chemical Bonds, Water Properties, and pH

Chapter 2: Chemical Foundations of Biology

Definitions of Key Terms

This section introduces essential vocabulary for understanding the chemical basis of life. Mastery of these terms is crucial for success in General Biology.

• Trace Elements: Small amounts of elements found in the body that are necessary for biological functions. Examples: Iron, Iodine, Zinc.

• Atomic Mass: The total mass of an atom, calculated as the sum of protons and neutrons.

• Atomic Number: The number of protons in an atom; determines the element's identity.

• Electromagnetivity: The tendency of an atom to attract electrons in a chemical bond.

• Ion: An atom which is negatively or positively charged due to loss or gain of electrons.

• Cation: A positively charged ion.

• Anion: A negatively charged ion.

• Cohesion: The tendency of molecules (especially water) to stick together due to hydrogen bonding.

• Adhesion: The tendency of different types of molecules to stick together.

Major Elements in Organisms

Living organisms are primarily composed of a few major elements, with trace elements required in smaller amounts for specific functions.

• Major Elements: Oxygen, Nitrogen, Carbon, Hydrogen.

• Trace Elements: Iron, Iodine, Zinc.

Determining Atomic Structure

Understanding the structure of atoms is fundamental to biology, as it underpins chemical reactions and molecular interactions.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Atomic Number: Number of protons in the atom.

• Mass Number: Number of protons plus neutrons.

Formulas:

• $\text{Mass number} = \text{protons} + \text{neutrons}$

• $\text{Atomic number} = \text{protons}$

Isotopes and Radioactivity

Isotopes are variants of elements with different numbers of neutrons. Some isotopes are radioactive and have important applications in science and medicine.

• Isotope: Variation of a chemical element caused by difference in amount of neutrons.

• Radioactive Isotope: Releases radiation when nucleus of an atom spontaneously decays.

• Applications: Used medically to test and diagnose people; used to carbon date fossils to determine their age.

Chemical Bonds

Covalent Bonds

Covalent bonds involve the sharing of electron pairs between atoms, resulting in stable molecules.

• Covalent Bond: A bond between two atoms that share electrons to complete a full outer shell.

• Single, Double, Triple Bonds: Refers to the number of shared electron pairs.

• Polar Covalent Bond: Electrons are shared unequally, resulting in partial charges (e.g., water molecule).

• Nonpolar Covalent Bond: Electrons are shared equally, resulting in no charge separation.

Ionic Bonds

Ionic bonds are formed when one atom donates electrons to another, resulting in oppositely charged ions that attract each other.

• Ionic Bond: A bond made by sharing electrons; generally weaker than covalent bonds.

Properties of Water

Hydrogen Bonds

Hydrogen bonds are weak attractions between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another. These bonds are crucial for many of water's unique properties.

• Hydrogen Bond: Weak bond between water molecules, but present in large numbers so water becomes strong.

Surface Tension and Cohesion

Water exhibits high surface tension and cohesion due to hydrogen bonding, which affects biological processes such as transport in plants.

• Surface Tension: Measurement of how difficult it is to break the surface of a liquid.

• Cohesion: Tendency of water molecules to stick together.

• Adhesion: Tendency of water molecules to stick to other substances.

Solutions and Solvents

Water is known as the universal solvent due to its ability to dissolve many substances, facilitating chemical reactions in living organisms.

• Solvent: A liquid that contains two or more substances.

• Solute: The thing that dissolves in something in a solution.

• Aqueous Solution: Solution where water is the solvent.

pH and Acidity

Understanding pH

pH is a measure of how acidic or basic a solution is, which is important for biological systems and chemical reactions.

• pH: Potential Hydrogen; measures how acidic or basic a solution is.

• Acid: Substance that donates hydrogen ions to solutions.

• Base: Substance that reduces the amount of hydrogen ions in a solution.

• Low pH (1-6): More acidic, more H+.

• High pH (8-14): More basic, more OH-.

• Neutral pH: pH 7 (Pure Water).

• Each step in pH: 10x more than the one before.

• pH 9: 10,000 more basic than pH 4.

• pH Measurement: pH is measured on a log scale.

Environmental Chemistry: Coral Reefs and Ocean Acidification

Impact of Carbon Dioxide on Coral Reefs

Atmospheric carbon dioxide affects ocean chemistry, which in turn impacts coral reefs and marine life.

• CO2: Produced by fossil fuel combustion; absorbed by the oceans.

• Ocean Acidification: CO2 dissolves into ocean and lowers pH (higher acidity).

• Calcification: The process in which coral reefs pull carbonate and calcium from seawater to form their structures.

• Effect of Acidification: When the ocean becomes more acidic, water has less carbonate and it is harder for corals to form their structures.

Bond Type	Strength	Example
Covalent	Strong	Water (H2O), Oxygen (O2)
Ionic	Moderate	Salt (NaCl)
Hydrogen	Weak (but strong in numbers)	Between water molecules

pH Value	Type	Example
1-6	Acidic	Lemon juice, stomach acid
7	Neutral	Pure water
8-14	Basic	Soap, bleach

Additional info: Some definitions and examples have been expanded for clarity and completeness. The notes are organized to cover all major points from the provided materials, with extra academic context added for self-contained study.