Unit 2

Biology 112 Unit Two

Chapter Three: Organic Compounds

  • Organic compounds are integral to life and are synthesized by cells.

  • Carbon Atoms in Organic Compounds:

    • Carbon has four outer shell electrons.

    • It forms four covalent bonds which allow for various structures and functionalities.

Carbon Skeletons

  • Characteristics of Carbon Skeletons:

    • Length: Skeletons can vary in length (e.g., Ethane, Propane).

    • Branching: Skeletons can be unbranched or branched (e.g., Butane and Isobutane).

    • Double Bonds: Skeletons may exhibit double bonds which can vary in location (e.g., 1-Butene, 2-Butene).

    • Rings: Carbon skeletons can form rings (e.g., Cyclohexane, Benzene).

Functional Groups

  • Importance of Functional Groups:

    • Functional groups behave consistently across different organisms and are essential for the chemistry of life.

    • The five primary functional groups include:

    • Hydroxyl (-OH): Characterized as polar; found in alcohols.

    • Carbonyl (C=O): Found in ketones and aldehydes.

    • Carboxyl (-COOH): Acts as an acid; found in carboxylic acids.

    • Amino (-NH2): Acts as a base; part of amino acids.

    • Phosphate (-OPO3²-): Important in energy transfer through molecules like ATP.

    • All functional groups are polar.

Macromolecules

  • Types of Macromolecules:

    • Monomers: Small organic molecules, serve as subunits.

    • Polymers: Chains formed by linking monomers, can consist of two up to thousands of monomers.

Dehydration Synthesis

  • Process: In dehydration synthesis, monomers are linked together, and a molecule of water is removed (one H+ and one OH-). This process characterizes anabolism, leading to polymer formation.

    • Illustration: Unlinked monomer + Short polymer ➔ Longer polymer

    • Energy Requirement: Energy is used in this process.

Hydrolysis

  • Definition: Hydrolysis is the reaction where a polymer is broken down into its monomers by the addition of water, replacing the H+ and OH- removed during dehydration synthesis.

    • Characterized by catabolism, which also requires energy.

Overview of Macromolecule Types and Functions

  • Carbohydrates:

    • Serving as energy sources or structural components (e.g., sugars).

  • Lipids:

    • Function in energy storage and cell membranes; not polymeric.

  • Proteins:

    • Functions include structural, transport, enzymatic, etc.

  • Nucleic Acids:

    • Store genetic information (e.g., DNA and RNA).

Carbohydrates

  • Structure:

    • Can be monosaccharides (single sugars), disaccharides (two sugars), or polysaccharides (multiple sugars).

  • Monosaccharides:

    • Simple sugars, e.g., Glucose; with a chemical formula typically in a 1:2:1 ratio of C:H:O.

  • Disaccharides:

    • Formed from two monosaccharides through dehydration synthesis.

    • Examples include:

    • Maltose: Glucose + Glucose

    • Sucrose: Glucose + Fructose

  • Polysaccharides:

    • Large carbohydrates made of hundreds to thousands of monosaccharides. Key examples include:

    • Starch: Energy storage in plants.

    • Glycogen: Energy storage in animals (liver, muscle).

    • Cellulose: Major structural component of plant cell walls, indigestible by many organisms.

    • Chitin: Structural component of exoskeletons in arthropods.

Lipids

  • Composition:

    • Mainly made of Carbon (C) and Hydrogen (H), connected by nonpolar covalent bonds, making them hydrophobic.

  • Monomers: Consist of glycerol and fatty acids joined through dehydration synthesis.

  • Types of Lipids:

    • Fats: Formed from glycerol and fatty acids.

    • Saturated Fats: Contain only single bonds (solid at room temperature).

    • Unsaturated Fats: Contain double bonds (liquid at room temperature).

    • Phospholipids: Major components of cell membranes containing phosphorus.

    • Waxes: Fatty acids bonded to alcohols; used for protection and waterproofing.

    • Steroids: Composed of four fused carbon rings; cholesterol serves as a precursor to many hormones.

Proteins

  • Building Blocks: Comprised of amino acids, of which there are 20 different types. Each amino acid has:

    • An amino group on one side and a carboxyl group on the other.

    • Varied properties (hydrophobic vs. hydrophilic) affecting their structure and function.

  • Polymers: Polypeptides, can range from hundreds to thousands of amino acids long, formed through dehydration synthesis (linking the amino group of one amino acid to the carboxyl group of another).

Types of Proteins

  • Structural Proteins: Provide support, e.g., collagen in connective tissues.

  • Contractile Proteins: Enable movement, e.g., muscle fibers.

  • Storage Proteins: Store amino acids, e.g., ovalbumin in egg whites.

  • Signal Proteins: Assist in cell communication, e.g., hormones like insulin.

  • Defensive Proteins: Protect against pathogens, e.g., antibodies.

  • Transport Proteins: Carry substances within the body, e.g., hemoglobin.

  • Enzymes: Catalyze biochemical reactions, controlling metabolism.

Structure of Proteins

  • Levels of Protein Structure:

    • Primary Structure: Linear sequence of amino acids linked by peptide bonds.

    • Secondary Structure: Local folding of the polypeptide chain, often into alpha helices or beta-pleated sheets stabilized by hydrogen bonds.

    • Tertiary Structure: Overall three-dimensional shape due to interactions between R groups (side chains) of amino acids.

    • Quaternary Structure: Complex formation of multiple polypeptide chains, each in its tertiary structure (e.g., hemoglobin).

  • Shape and Function: The specific shape of proteins determines their function. Denaturation occurs due to factors such as temperature, salt concentration, or pH, affecting functionality.

Nucleic Acids

  • Polymers: Consist of nucleotides, which contain a sugar, a phosphate group, and a nitrogenous base.

  • Genetic Material: The sequence of nucleotides constitutes genes that code for proteins.

Differences Between DNA and RNA

  • DNA (Deoxyribonucleic acid):

    • Sugar: Deoxyribose.

    • Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

    • Structure: Double helix, remains in the nucleus, used for information transfer with long sequences of base pairs.

    • Base pairing: A pairs with T and C pairs with G; hydrogen bonds hold the structure.

  • RNA (Ribonucleic acid):

    • Sugar: Ribose.

    • Bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G).

    • Structure: Typically single-stranded, involved in protein production, transports information from the nucleus.

    • Base pairing: A pairs with U and C pairs with G.