Understanding the pH Scale and Biomolecule Chemistry

The pH Scale and Acidity Measurement

The pH scale is a system that measures the acidity of a substance. It is ranked from 1 to 14, with 1 being the most acidic and 14 being the most alkaline; 7 is neutral. The pH represents the concentration of hydrogen ions (H+) in a substance and is measured using the pH scale.

Buffers: Maintaining pH Balance

Buffers are substances that tend to maintain a constant pH by liberating or capturing H+ ions. If blood becomes too acidic, bicarbonate accepts H+ ions, and carbonic acid is formed. If it becomes too basic, carbonic acid liberates H+ ions to interact with OH- ions to form water.

Major Classes of Biomolecules

Biomolecules are any molecules produced by a living organism. The four main groups are:

• Nucleic Acids
• Proteins
• Carbohydrates
• Lipids

Examples of Biomolecules:

• Proteins: Meat, fingernails, hair.
• Lipids: Fat, oil, wax.
• Carbohydrates: Sugar and starch.
• Nucleic Acids: DNA, RNA.

The Role of Carbon in Life

Carbon is the basis of biomolecules due to its capacity for forming a maximum of eight electrons in its outer shell. Biomolecules are formed by a skeleton of carbon and hydrogen attached to a functional group.

Biological Molecules: Structure and Reactions

Functional Groups and Molecular Formation

Functional groups participate in chemical reactions and give identity to the biomolecules. Organic molecules are formed by joining small molecules one after another. Small molecules are called monomers, and long chains of monomers form polymers.

Key Molecular Reactions:

• Dehydration Synthesis: This occurs when one molecule of water is lost during the formation of a new, larger molecule.
• Hydrolysis: This process breaks a molecule into smaller units by adding water.

Carbohydrates

Carbohydrates are either small, water-soluble sugars or polymers of sugar.

Classification by Size:

• Monosaccharide: 1 molecule (e.g., glucose, fructose, galactose). Glucose is the most common monosaccharide in organisms.
• Disaccharide: 2 molecules.
• Polysaccharide: 3 or more molecules.

Artificial Sweeteners

Artificial sweeteners duplicate the effect of sugar (e.g., potassium, sucralose, saccharin).

Lipids

Lipids are biomolecules (like fat and cholesterol) that consist largely of only C, H, and O. They are hydrophobic, nonpolar, and non-soluble in water.

Main Categories of Lipids:

• Oils, fats, and waxes.
• Steroids (e.g., cholesterol, which we produce).
• Phospholipids (which make up the cell membrane).

Lipids are made of fatty acids (monomers). There are two types: saturated and unsaturated. They are called unsaturated because two carbons do not have the maximum number of hydrogen atoms attached (i.e., they have one or more double bonds between carbons). In unsaturated fatty acids, we can find:

• Monounsaturated (one double bond).
• Polyunsaturated (two or more double bonds).