Biological Molecules Lecture Review

Inorganic Molecules:
- Lack carbon.
- Play important roles in an organism's metabolism.
- Excluding water, they make up only $1.5\%$ of an organism's mass.
Organic Molecules:
- Contain carbon and are necessary for life.
- Generally larger and more complex than inorganic molecules ( $macromolecules$ ).
- Consist of four main families of macromolecules:
  - Carbohydrates
  - Lipids
  - Proteins
  - Nucleic Acids

Atomic Structure: Carbon atoms form four covalent bonds with four same or four different atoms or molecules.
Carbon Chains:
- Vary in length.
- Can be unbranched or highly branched.
- Carbon skeletons can contain double bonds.
- Carbon skeletons can be arranged in rings.

Definition: Isomers possess the same number and type of atoms (identical molecular formula) but differ in the arrangement of atoms, especially around a central carbon atom. This difference in arrangement leads to distinct structures and functions.
Types of Isomers: There are three main types:
- Structural Isomers: Have the same number and types of atoms, but their carbon skeletons differ in branching patterns.
- Geometric Isomers: Share the same number and type of atoms, but differ in the orientation of atoms around a double bond. This leads to trans (atoms on opposite sides) versus cis (atoms on the same side) configurations.
- Enantiomers (Mirror Images): Possess the same number and type of atoms, but are arranged as non-superimposable mirror images around a central carbon atom.

Definition: Functional groups are specific atoms or molecules attached to a carbon chain that are responsible for particular chemical properties.
Hydrocarbon: The simplest functional group, consisting of a hydrogen atom attached to a carbon chain.
Specific Functional Groups:
- Hydroxyl Group ( $−OH$ ): A hydrogen and oxygen atom bonded to a carbon. Compounds containing this group are called alcohols.
- Carbonyl Group ( $−C=O$ ): An oxygen atom double-bonded to a carbon atom. Found in aldehydes (if on end of chain) and ketones (if within the chain).
- Carboxyl Group ( $−COOH$ ): A carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group. This group acts as an acid.
- Amino Group ( $−NH_2$ ): A nitrogen atom bonded to two hydrogen atoms and a carbon atom. This group is characteristic of amino acids, which are the building blocks of proteins.
- Phosphate Group ( $−PO_4$ ): A phosphorus atom bonded to four oxygen atoms. Crucial components of DNA and ATP.
- Methyl Group ( $−CH_3$ ): A carbon atom bonded to three hydrogen atoms. This group can affect the expression of genes, a process known as epigenetics.

Monomer: Represents a single unit or a basic building block.
Polymer: A large molecule (macromolecule) formed by linking many individual monomers together.
Making & Breaking Polymers:
- Dehydration Reaction (Condensation Reaction): A chemical reaction that forms a covalent bond between two smaller polymers by removing a water molecule ( $H_2O$ ). This process links monomers to create polymers.
- Hydrolysis: A chemical reaction that breaks bonds within a polymer by the insertion of a water molecule ( $H_2O$ ). This process breaks polymers down into monomers.

Functions:
- Primary source of energy.
- Energy storage.
- Provide structural support.
Simplest Unit (Monomer): Monosaccharide (one sugar unit).
Types of Carbohydrates:
- Monosaccharides (Simple Sugars): The simplest carbohydrates.
  - Examples:
    - Fructose: Commonly found in fruit.
    - Ribose and Deoxyribose: Fundamental building blocks for nucleic acids (RNA and DNA, respectively).
    - Glucose: A primary energy source for cells and a precursor for many other organic molecules.
- Disaccharides: Formed by a dehydration synthesis reaction linking two monosaccharides.
  - Examples:
    - Lactose (milk sugar): Composed of glucose plus galactose.
    - Sucrose (table sugar): Composed of glucose plus fructose.
    - Maltose (found in beer): Composed of glucose plus glucose.
- Polysaccharides (Complex Carbohydrates): Consist of many sugar units (which can be the same or different) covalently linked to form long chains. These primarily function in energy storage and structural support.
  - Examples:
    - Glycogen: Used for energy storage in animal tissues (e.g., liver and muscle cells).
    - Starch: Used for energy storage in plants.
    - Cellulose (Fiber): Forms the rigid structure of plant cell walls.

Properties: Lipids are hydrophobic, meaning they do not dissolve in water.
Functions:
- Store energy and serving as a concentrated source of energy storage.
- Form the primary component of cell membranes.
- Protect organs from physical shock.
- Provide insulation against cold temperatures.
- Act as steroid hormones (e.g., sex hormones).
Simplest Unit: Fatty acid chain.
Types of Lipids:
- Fats (Triglycerides): Involved in energy, energy storage, organ protection, and insulation.
- Phospholipids: The main component of cell membranes.
- Sterols: Components of animal cell membranes and serve as precursors for steroid hormones.
- Waxes: Prevent water loss in plants and waterproof animal coverings (e.g., feathers).
Fats and Oils (Triglycerides):
- A fat molecule consists of three fatty acid chains linked to one glycerol molecule.
- Fatty acid chains vary significantly in length, typically from $8$ to $48$ carbon atoms.
- Oils are simply fats that are liquid at room temperature.
Saturated vs. Unsaturated Fats:
- Saturated Fats:
  - Contain only single carbon bonds within their fatty acid chains.
  - Are