Functional Groups Graphic Organizer

Functional Groups in Biological Molecules

• Overview of Functional Groups

  • Functional groups are specific assemblies of atoms attached to carbon backbones that confer distinctive chemical properties and reactivity to biological molecules.
  • They determine molecular solubility, polarity, acidity or basicity, and hydrogen bonding behavior in cellular environments.

• Hydroxyl Group

  • Structure and Molecular Formula: $R-OH$ (or $-OH$ functional group)
  • Compound Class: Alcohol
  • Characteristics and Functional Properties:
  • Highly polar due to the strong electronegativity of oxygen.
  • Readily forms hydrogen bonds with water and other polar molecules.
  • Hydrophilic (water-soluble) in nature.
  • Representative Example: Ethanol

• Carbonyl Group

  • Structure and Molecular Formula: $R-C=O$ (or $-C=O$ functional group)
  • Compound Class Classification:
  • Ketone: Occurs when the carbonyl group is located within the interior of a carbon chain.
  • Aldehyde: Occurs when the carbonyl group is located at the terminal end of a carbon chain.
  • Characteristics and Functional Properties:
  • Polar functional group.
  • Forms hydrogen bonds.
  • Highly reactive in chemical and metabolic pathways.
  • Representative Examples:
  • Ketone Example: Acetone
  • Aldehyde Example: Formaldehyde

• Carboxyl Group

  • Structure and Molecular Formula: $R-COOH$ (or $-COOH$ functional group)
  • Compound Class: Carboxylic acid
  • Characteristics and Functional Properties:
  • Polar and hydrophilic.
  • Possesses acidic properties; donates a hydrogen ion ($H^+$) into aqueous solutions, altering pH.
  • Forms hydrogen bonds.
  • Representative Example: Acetic acid

• Amino Group

  • Structure and Molecular Formula: $R-NH_2$ (or $-NH_2$ functional group)
  • Compound Class: Amine
  • Characteristics and Functional Properties:
  • Polar functional group.
  • Possesses basic properties; acts as a proton acceptor in biological contexts.
  • Participates in hydrogen bonding.
  • Representative Example: Glycine (an amino acid)

• Sulfhydryl Group

  • Structure and Molecular Formula: $R-SH$ (or $-SH$ functional group)
  • Compound Class: Thiol
  • Characteristics and Functional Properties:
  • Polar functional group.
  • Forms covalent disulfide bonds ($S-S$ linkages/bridges) between cysteine residues, providing crucial stabilization to tertiary and quaternary protein structures.
  • Representative Example: Cysteine (an amino acid)

• Phosphate Group

  • Structure and Molecular Formula: $R-PO_4$ (or $-PO_4$ functional group / phosphate ester)
  • Compound Class: Phosphate ester
  • Characteristics and Functional Properties:
  • Polar and highly acidic.
  • Carries negative charges in neutral biological solutions.
  • Serves a central role in energy storage/transfer and the structural backbone of nucleic acids.
  • Representative Example: ATP (adenosine triphosphate)

• Methyl Group

  • Structure and Molecular Formula: $R-CH_3$ (or $-CH_3$ functional group)
  • Compound Class: Alkane
  • Characteristics and Functional Properties:
  • Nonpolar functional group.
  • Hydrophobic (water-fearing) behavior.
  • Involved in biological regulation, including DNA methylation and control of gene expression.
  • Representative Example: Methane

Biological Macromolecules

• Carbohydrates

  • Elements Involved: Carbon ($C$), Hydrogen ($H$), and Oxygen ($O$)
  • Stoichiometric Formula Ratio: $CH_2O$
  • Monomer (Sub-unit): Monosaccharide
  • Polymer: Polysaccharides
  • Biological Roles: Serves as direct chemical energy, energy storage, and structural support in organisms.

• Lipids

  • Elements Involved: Primarily Carbon ($C$), Hydrogen ($H$), and Oxygen ($O$); occasionally contains Phosphorus ($P$)
  • Monomer (Sub-units): Fatty acids and Glycerol
  • Polymer: Does not contain true polymers
  • Biological Roles: Long-term energy storage, membrane structure (phospholipid bilayer), and molecular signaling.

• Nucleic Acids

  • Elements Involved: Carbon ($C$), Hydrogen ($H$), Oxygen ($O$), Nitrogen ($N$), and Phosphorus ($P$)
  • Monomer (Sub-unit): Nucleotides
  • Polymer: Polynucleotides (DNA/RNA)
  • Biological Roles: Encodes, stores, transmits, and expresses genetic information.

• Proteins

  • Elements Involved: Carbon ($C$), Hydrogen ($H$), Oxygen ($O$), Nitrogen ($N$), and Sulfur ($S$)
  • Monomer (Sub-unit): Amino acids
  • Polymer: Polypeptides
  • Biological Roles: Enzymatic catalysis, structural support, cellular transport, immune response, and mechanical movement.