Biology Chemistry Overview

Overview

This lecture reviews the foundational chemistry of biology, including water properties, the elements of life, and the structure and function of biomolecules: carbohydrates, lipids, proteins, and nucleic acids.

Water and Hydrogen Bonding

• Water is a polar molecule with unequal sharing of electrons between oxygen (partial negative) and hydrogen (partial positive).
• Hydrogen bonds are weak intermolecular bonds between molecules, not within them.
• Hydrogen bonds are crucial for DNA, RNA, protein structures, and many biological functions.
• Cohesion is hydrogen bonding between water molecules, causing high surface tension and heat capacity.
• Adhesion is water molecules sticking to other substances, key for processes like transpiration in plants.
• Surface tension results from cohesion, creating a "web" at water's surface.

Acids, Bases, and pH

• Acidic solutions have more hydrogen ions (H⁺); pH below 7.
• Basic solutions have more hydroxide ions (OH⁻); pH above 7.

Elements of Life

• Main elements: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur (CHNOPS).
• Carbon is central to biomolecule structure; phosphorus is key in ATP and DNA.
• Hydrogen ions are important for energy gradients and acidity.

Monomers, Polymers, and Functional Groups

• Monomers are small building blocks; polymers are large molecules made from monomers.
• Dehydration synthesis removes water to join monomers into polymers.
• Hydrolysis adds water to split polymers into monomers.
• Key functional groups: phosphate (energy transfer), methyl (DNA silencing, nonpolar), hydroxyl and carbonyl (polar, water-soluble), carboxyl and amino (amino acids), sulfhydryl (protein stabilization), acetyl (DNA activation).

Carbohydrates

• Monomers: monosaccharides (simple sugars like glucose).
• Disaccharides: two linked simple sugars (e.g., lactose).
• Polysaccharides: storage (starch, glycogen) or structural (cellulose).
• Most animals can’t digest cellulose; some rely on microorganisms for this.
• Lactose intolerance results from lack of lactase enzyme production in adulthood.

Lipids

• Lipids are mostly nonpolar (hydrophobic) and do not have repeating monomers.
• Functions: energy storage (fats/oils), waterproofing (waxes), membrane structure (phospholipids), signaling (steroids).
• Phospholipids form bilayers in membranes with hydrophilic heads and hydrophobic tails.

Proteins

• Monomers: amino acids (20 types, differ by R group/side chain).
• Four levels of structure: primary (amino acid sequence), secondary (alpha helices/beta sheets from hydrogen bonds), tertiary (side chain interactions), quaternary (multiple peptide chains).
• Hemoglobin is a quaternary protein; sickle cell disease is caused by a mutation altering its structure.

Nucleic Acids (DNA and RNA)

• Functions: genetic information storage (DNA), information transfer and functionality (RNA).
• Monomers: nucleotides, each with a sugar, phosphate group, and nitrogenous base.
• DNA: deoxyribose sugar, bases A, T, C, G; double helix, antiparallel strands.
• RNA: ribose sugar, bases A, U, C, G; single-stranded, various structures.
• Nucleotides link via sugar-phosphate bonds; strands pair via hydrogen bonds (A-T/U, C-G).
• DNA and RNA synthesis occurs in the 5′ to 3′ direction.

Key Terms & Definitions

• Polar Molecule — molecule with unequal electron distribution causing partial charges.
• Hydrogen Bond — weak attraction between polar molecules.
• Cohesion — attraction between like molecules (e.g., water to water).
• Adhesion — attraction between different substances (e.g., water to plant cell walls).
• Monomer — small molecule that can join to form polymers.
• Polymer — large molecule made from monomers.
• Dehydration Synthesis — reaction that joins monomers by removing water.
• Hydrolysis — reaction that breaks polymers using water.
• Amino Acid — building block of proteins.
• Nucleotide — building block of nucleic acids.

Action Items / Next Steps

• Download and complete the unit one checklist from apbiosuccess.com/checklist.
• Review the four biomolecules and their structures.
• Practice identifying the properties and functions of water.
• Study the structure and function of monomers and polymers.
• Prepare for questions on hydrogen bonding, protein structure, and nucleic acid directionality.