Introduction To Macromolecules

Introduction to Cells at a Molecular Level

Overview: The Molecules of Life

• All living things consist of four primary classes of large biological molecules:

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic Acids

• Molecular Structure Determines Function

  • The function of a molecule is inherently linked to its structure.

Small Organic Molecules

• Small organic molecules can combine to form larger molecules known as Macromolecules.

• Definition:

  • Macromolecules: Large molecules made up of lots of covalently connected atoms.

  • Representative structure of covalent bonding:

  • Hydrogen and Carbon atoms contributing electrons in covalent bonds.

Macromolecules as Polymers

• Polymers: Macromolecules that are constructed from monomer building blocks.

• Definition:

  • Polymer: A long molecule consisting of many similar building blocks (monomers).

• Three classes of life’s organic molecules that are polymers:

  • Carbohydrates

  • Proteins

  • Nucleic Acids

The Synthesis of Polymers

• Condensation Reaction/Dehydration Reaction:

  • Occurs when two monomers bond together, resulting in the loss of a water molecule.

• Visualization:

  • During dehydration, a water molecule (H₂O) is removed to form a new bond.

  • Represented as:

  • Short polymer + Unlinked monomer → Longer polymer + H₂O

The Breakdown of Polymers

• Hydrolysis:

  • A reaction that disassembles polymers into monomers by adding a water molecule.

• Definition:

  • Hydrolysis is essentially the reverse reaction of dehydration.

• Visualization:

  • Hydrolysis represented as:

  • Polymer + H₂O → Monomer + Bond broken

Reaction Rates

• Both dehydration and hydrolysis reactions occur slowly without the assistance of enzymes.

• Enzymes:

  • Macromolecules that catalyze and speed up these biochemical processes.

The Diversity of Polymers

• Each cell contains thousands of distinct types of macromolecules.

• Variation among macromolecules:

  • These macromolecules differ among cell types within an organism and have even greater variation among different species.

• The immense variety of polymers arises from a limited set of monomers, enabling diverse biological functions.

Chirality

• Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image.

• Example molecular structures demonstrating chirality:

  • The arrangement of atoms and groups around a central carbon creates two possible configurations.

  • This is also deduced when molecular structures contain 4 different groups around a carbon

Chemical Groups and Their Properties

• Overview of common chemical groups involved in biological molecules:

  • Hydroxyl Group (-OH)

  • Compound Name: Alcohol

  • Example: Ethanol (H-C-C-OH)

  • Carbonyl Group (>C=O)

  • Compound Names: Ketone, Aldehyde

  • Examples: Acetone (H-C-C(=O)-H)

  • Carboxyl Group (-COOH)

  • Compound Name: Carboxylic Acid or Organic Acid

  • Example: Acetic Acid (H-C(-COOH)-H)

  • Amino Group (-NH₂)

  • Compound Name: Amine

  • Example: Glycine (H-NH₂-C)

  • Sulfhydryl Group (-SH)

  • Compound Name: Thiol

  • Example: Cysteine (H-C-CH₂-SH)

  • Phosphate Group (-OPO₃²⁻)

  • Compound Name: Organic Phosphate

  • Example given structurally depicted.

  • Methyl Group (-CH₃)

  • Compound Name: Methylated Compound

  • Example: 5-Methylcytosine (N-CH₃)