Chemistry of Life

Acids, Bases, and Buffers

Acids, bases, and buffers are essential for maintaining pH balance in biological systems. Understanding their properties helps explain how organisms regulate internal environments.

• Acids are substances that increase the concentration of hydrogen ions (H+) in a solution.

• Bases decrease H+ concentration, often by increasing hydroxide ions (OH-).

• Buffers are solutions that resist changes in pH when acids or bases are added.

• Key Equation:

• Example: The bicarbonate buffer system in blood helps maintain pH homeostasis.

Comparison Table: Acids vs. Bases

Water and Biological Molecules

Hydrophilic and Hydrophobic Substances

Water interacts differently with various substances, influencing biological structure and function.

• Hydrophilic substances (e.g., salts) dissolve easily in water due to their polarity.

• Hydrophobic substances (e.g., lipids) do not dissolve in water and tend to aggregate.

• Example: Cell membranes are formed by hydrophobic lipid bilayers.

Table: Water Interactions

Carbon Chemistry

Significance of Carbon

Carbon is the backbone of organic molecules due to its unique bonding properties.

• Carbon can form four covalent bonds, allowing for diverse molecular structures.

• Example: Glucose, DNA, and proteins all contain carbon skeletons.

Hydrocarbons

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen.

• Definition: Molecules with only C and H atoms.

• Chemical Properties: Nonpolar, hydrophobic, high energy content.

• Energy Release: Combustion of hydrocarbons releases energy.

Functional Groups

Functional groups are specific groups of atoms within molecules that confer particular chemical properties.

• Seven critical functional groups: hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl.

• Properties and Roles:

  • Hydroxyl (-OH): Polar, forms hydrogen bonds, found in alcohols.

  • Carbonyl (C=O): Found in sugars, increases reactivity.

  • Carboxyl (-COOH): Acidic, found in amino acids and fatty acids.

  • Amino (-NH2): Basic, found in amino acids.

  • Sulfhydryl (-SH): Forms disulfide bonds in proteins.

  • Phosphate (-PO4): Energy transfer, found in ATP and nucleic acids.

  • Methyl (-CH3): Nonpolar, affects gene expression.

Energy in Biological Systems

Adenosine Triphosphate (ATP)

ATP is the primary energy currency of the cell, storing and releasing energy for cellular processes.

• Definition: ATP is a nucleotide with three phosphate groups.

• Energy Storage: Energy is stored in the bonds between phosphate groups.

• Hydrolysis Reaction:

• Example: Muscle contraction and active transport use ATP.

Macromolecules

Definition and Significance

Macromolecules are large, complex molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Provide energy and structural support.

• Lipids: Store energy, form membranes, and act as signaling molecules.

• Proteins: Catalyze reactions, provide structure, and regulate processes.

• Nucleic Acids: Store and transmit genetic information.

Carbohydrates

Carbohydrates are composed of monosaccharides, disaccharides, and polysaccharides.

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

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Long chains (e.g., starch, cellulose).

• Function: Energy storage and structural support.

Polymer Synthesis and Breakdown

Polymers are formed by joining monomers through dehydration synthesis and broken down by hydrolysis.

• Dehydration Synthesis:

• Hydrolysis:

Lipids

Lipids include triglycerides, phospholipids, and steroids, each with distinct roles in cells.

• Triglycerides: Energy storage.

• Phospholipids: Major component of cell membranes.

• Steroids: Hormones and membrane structure.

• Saturated vs. Unsaturated Fats: Saturated fats have no double bonds; unsaturated fats have one or more, affecting fluidity.

Proteins

Proteins are polymers of amino acids with diverse functions.

• Amino Acids: Building blocks of proteins.

• Peptide Bonds: Link amino acids together.

• Levels of Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets.

  • Tertiary: 3D folding.

  • Quaternary: Multiple polypeptides.

• Denaturation: Loss of structure due to heat, pH, or chemicals, affecting function.

Nucleic Acids

Nucleic acids (DNA and RNA) store genetic information and direct protein synthesis.

• Complementary Base Pairing: DNA: A-T, C-G; RNA: A-U, C-G.

• Significance: Ensures accurate genetic coding and transmission.