Cooper-Ch03_lecture

The Molecules of Cells

Organic Molecules

  • Definition: Organic molecules are defined as containing carbon atoms attached to hydrogen.

    • Examples include glucose and other carbohydrates.

  • Important Note: Carbon dioxide (CO2) is an exception, as it does not fit the definition of organic molecules.

Structural Models of Molecules

  • Types of Models:

    • Structural formula: Represents the arrangement of atoms in a molecule.

    • Ball-and-stick model: Visualizes the molecular geometry and bond angles.

    • Space-filling model: Displays the actual size of atoms and how they occupy space.

  • Carbon's Bonding Properties:

    • Carbon typically forms four single bonds arranged in a tetrahedral shape.

Chain Formation by Carbon

  • Chain Length:

    • Carbon skeletons can vary in length; examples include:

      • Ethane (C2H6)

      • Propane (C3H8)

  • Branching:

    • Carbon chains can be unbranched or branched. For instance:

      • Butane (C4H10) vs. Isobutane (C4H10)

Bond Types in Carbon Chains

  • Single vs. Double Bonds:

    • Carbon chains may contain double bonds, affecting their structure and properties.

    • Examples:

      • 1-Butene vs. 2-Butene (positioning of the double bond changes the structure).

Ring Structures

  • Carbon skeletons can be arranged in rings, such as those seen in cyclohexane or benzene.

    • In ring diagrams, carbon atoms are often placed at the corners, with hydrogen atoms filling the remaining bonds.

Functional Groups and Organic Compounds

  • Definition:

    • Functional groups are specific groups of atoms that provide organic compounds with distinct properties.

  • Nature of Functional Groups:

    • Compounds with hydroxyl (-OH), carbonyl (C=O), carboxyl (-COOH), amino (-NH2), and phosphate (-OPO3^2-) groups tend to be hydrophilic (water-loving).

Important Functional Groups

  • Hydroxyl Group:

    • Structure: -OH

    • Example: Alcohols

  • Carbonyl Group:

    • Structure: C=O

    • Types: Aldehydes and Ketones

  • Carboxyl Group:

    • Structure: -COOH

    • Example: Carboxylic acids

  • Amino Group:

    • Structure: -NH2

    • Example: Amines

  • Phosphate Group:

    • Structure: -OPO3^2-

    • Example: Organic phosphates

Hydrophobic Molecules

  • Definition:

    • Hydrophobic molecules, such as hydrocarbons, are water-repelling or avoiding due to their nonpolar nature.

  • Methyl Group:

    • Structure: -CH3; it is also hydrophobic.

Life's Organic Molecules

  • Main Categories:

    • Proteins (structure, enzymes)

    • Carbohydrates (sugars, starch, cellulose)

    • Lipids (fats, oils, hormones)

    • Nucleic acids (DNA, RNA, ATP)

Macromolecules, Monomers, and Polymers

  • Definitions:

    • Macromolecule: Large biological molecule typically with a mass of at least 1000 Daltons.

    • Monomer: Smaller subunit that can join together to form polymers.

    • Polymer: A chain of monomers.

  • Example Macromolecules: Starch, proteins, DNA.

  • Polymer Creation:

    • Dehydration Synthesis: Joins monomers to form polymers and removes water.

    • Hydrolysis: Breaks down polymers into monomers and adds water.

Proteins in Detail

  • Amino Acids:

    • Building blocks of proteins; contain a carboxylic acid group and an amino group.

    • There are 20 different amino acids, classified by their side chains (R groups).

  • Function of Proteins:

    • Include structural support, enzymatic activity, membrane transport, motile, regulatory, receptor, as well as hormones, antibodies, storage, and venomous functions.

Levels of Protein Structure

  • Primary Structure:

    • Sequence of amino acids.

  • Secondary Structure:

    • Stabilized by hydrogen bonds (e.g., alpha-helix and beta-sheet).

  • Tertiary Structure:

    • 3D arrangement based on R-group interactions.

  • Quaternary Structure:

    • Assembly of multiple polypeptides (e.g., hemoglobin).

Carbohydrates

  • Structure:

    • Composed mainly of carbon, hydrogen, and oxygen in a 1:2:1 ratio.

  • Types:

    • Monosaccharides (single sugars, e.g., glucose), disaccharides (two sugars, e.g., sucrose), polysaccharides (many sugars, e.g., starch, cellulose).

Lipids

  • Characteristics:

    • Composed mainly of fatty acids; hydrophobic and insoluble in water.

    • Types include triglycerides, phospholipids, and steroids.

  • Functions:

    • Energy storage, structure of cell membranes, waterproofing, and hormone production.

Nucleic Acids

  • Definition:

    • Composed of nucleotides, which include a nitrogen base, sugar, and phosphate group.

    • DNA and RNA are the main types, with DNA housing genetic information and RNA aiding in protein synthesis.

  • Base Pairing in DNA:

    • A-T and C-G pairings linked by hydrogen bonds.