Introduction to General Biology Concepts

This study guide covers foundational topics in General Biology, including the properties of water, acids and bases, biomolecules such as proteins, carbohydrates, and lipids, and their roles in living organisms. Understanding these concepts is essential for exploring biological processes at the molecular level.

Some Terms to Know

Basic Chemical Terms

• Element: A substance that contains just one type of atom.

• Compound: A substance formed when two or more different elements chemically combine (e.g., water, hydrogen cyanide).

• Molecule: The smallest part of a compound that still has the properties of that compound.

• Inorganic: Substances not composed of hydrogen and carbon.

• Organic: Substances containing hydrogen and carbon.

Properties of Water

Chemical Structure and Representation

• Water is represented by the chemical formula H2O.

• It contains two hydrogen atoms and one oxygen atom.

• Water molecules are held together by weak hydrogen bonds, which can break easily.

Characteristics of Water

• Absorbs and releases heat slowly, helping regulate body temperature.

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

• Liquid water is less dense than ice because the atoms in liquid water are packed closely together, while ice has a more open structure (density = mass/volume).

• Ice is the least dense phase of water, allowing it to float.

• Water is known as the universal solvent because it can dissolve many substances.

Table: States of Water and Density

Dissociation of Water

Process and Importance

• Water can undergo dissociation, breaking apart into ions.

• This process can be reversible or temporary, resulting in the formation of smaller molecules or atoms.

• When water dissociates, it forms two ions:

  • Atoms that carry a charge as a result of giving up or taking on electrons.

Acids & Bases

Definitions and Properties

• Acids: Molecules that dissociate in water and release hydrogen ions (H+).

• Bases: Molecules that either take up hydrogen ions or release hydroxyl ions (OH-).

pH Scale

• pH stands for "potential of hydrogen" and measures the acidity or basicity of a solution.

• Defined as the negative logarithm of the hydrogen ion concentration:

• Scale ranges from 0 to 14:

• Low pH = high concentration of hydrogen ions (acidic).

• High pH = low concentration of hydrogen ions (basic).

• Each pH unit represents a tenfold difference in hydrogen ion concentration.

Table: pH Scale Overview

Buffers

Role in Biological Systems

• Buffers help keep the pH steady in biological systems.

• They are chemicals or combinations of chemicals that resist changes in pH.

• Buffers help organisms maintain a relatively constant pH, which is crucial for enzyme function and metabolic processes.

Salts

Formation and Properties

• When an acid combines with a base, a salt and a water molecule are formed.

• A salt consists of:

  • The positive ion of the base

  • The negative ion of the acid

• Example:

Biomolecules

Major Types

• Proteins

• Carbohydrates

• Lipids

Proteins

Structure and Function

• Proteins are used for structure and support in organisms.

• They also act as enzymes (specialized proteins that act as catalysts to speed up body reactions).

• Proteins are made up of amino acids, which are held together by peptide bonds.

Levels of Protein Organization

Amino Acids

Properties and Importance

• Proteins are made up of 20 amino acids.

• The chemical properties of amino acids determine the biological activity of the protein.

• Amino acid sequences contain the necessary information to fold into a 3D structure, affecting protein stability.

Table: Essential and Non-Essential Amino Acids

Essential amino acids include: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, histidine, arginine (Additional info: Some sources may vary on histidine and arginine).

Carbohydrates

Structure and Types

• Carbohydrates are "hydrates of carbon" with a general formula of (CH2O)n.

• They are a primary energy source for living organisms.

• Three main types:

  • Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose)

  • Disaccharides: Made of two monosaccharides (e.g., maltose, sucrose, lactose)

  • Polysaccharides: Large molecules formed by combining many smaller molecules (e.g., starch, glycogen, cellulose)

Table: Types of Carbohydrates

Lipids

Types and Functions

• Lipids are fatty, waxy, or oily compounds that do not dissolve in water.

• They are used to store energy and support membranes in plants and animals.

• Four main types:

  • Fats & Oils

  • Fatty acids

  • Soaps

  • Steroids

Fats & Oils

• Composed of fatty acids and glycerol.

• Sweet, syrupy compounds, sometimes called triglycerides.

Fatty Acids

• Hydrocarbon chains containing 16-18 carbons ending with an acid group.

• Can be saturated (no double bonds) or unsaturated (one or more double bonds).

• Oils are liquid at room temperature due to unsaturation.

Soaps

• Not considered lipids, but contain lipids.

• Formed from a fatty acid and an inorganic base.

• Soaps are emulsifiers, helping mix water and oil.

Steroids

• Contain four fused carbon rings with different functional groups.

• Examples: cholesterol (regulates sodium), aldosterone, testosterone.

Additional info: Some amino acids listed as essential may vary depending on dietary requirements and age. The pH scale is logarithmic, meaning each unit change represents a tenfold change in hydrogen ion concentration.