BIOL L5

Key Terms and Chemical Structures

• Monomer: The basic building block of macromolecules.

• Amino Acid: Organic compounds that serve as the building blocks of proteins.

• Biological Macromolecules: Large molecules essential for life, primarily proteins, carbohydrates, lipids, and nucleic acids.

• Polymer: A large molecule made up of repeating structural units (monomers).

• Polypeptide: A chain of amino acids linked by peptide bonds, forming proteins.

• Cellular Structure: The arrangement and organization of cells and their components.

• Intermediate Filament: Part of the cytoskeleton that provides support and strength to the cell.

Chemical Formula Examples

• CH3 (methyl group)

• H (hydrogen)

• N-C-C-OH (general structure of an amino acid)

• Ala (Alanine), Val (Valine), Ser (Serine)

Biomolecules & Macromolecules

Major Classes of Biomolecules

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

Functionality

The structure (size and shape) of biomolecules directly influences their function.

Monomers & Polymers

• Carbohydrates: Chains of sugar monomers.

• Proteins: Chains of amino acid monomers.

• Nucleic Acids: Chains of nucleotide monomers.

• Polymers: Long chains formed from repeated monomers.

Synthesis by Dehydration

• Dehydration Reaction: Process that removes a water molecule to form a bond.

  • Example Process: Unlinked monomer + unlinked monomer → Short polymer (with water removed).

  • Visual Representation: Formation of longer polymers through multiple dehydration reactions.

Disassembly by Hydrolysis

• Hydrolysis Reaction: Process that adds a water molecule to break a bond.

  • Example Process: Polymer + water → shorter polymers.

Carbohydrates

• Definition: Macromolecules formed from sugars and their polymers.

Types of Carbohydrates

1. Simple Carbohydrates:

   • Monosaccharides: The simplest form (e.g., glucose).

   • Disaccharides: Formed from two monosaccharides.

   • Polysaccharides: Large polymers of sugars (e.g., starch, cellulose).

Monosaccharides

• Chemical Formula: (CH2O)n

• Structure: Consists of a carbonyl group and multiple hydroxyl groups.

  • Types:

    • Aldose: Contains an aldehyde group.

    • Ketose: Contains a ketone group.

Aldose vs. Ketose

• Examples:

  • Glyceraldehyde: Aldose example.

  • Dihydroxyacetone: Ketose example.

Variation in Length of Monosaccharides

• Triose: Sugars with 3 carbons (C3H6O3).

• Pentose: Sugars with 5 carbons (C5H10O5).

• Hexose: Sugars with 6 carbons (C6H12O6), e.g., glucose.

Sugar Structure

• Formation of Rings: Many 5 & 6 carbon sugars form ring structures in an aqueous environment, which affects their chemical behavior.

Disaccharides

• Structure: Composed of two monosaccharides linked by a glycosidic bond.

  • Examples:

    • Maltose: Composed of glucose monomers.

    • Sucrose: Composed of glucose and fructose.

Glycosidic Linkages

• Context: Glycosidic bonds can form between different carbon atoms.

  • Linkage Types:

    • Alpha Linkage: O atom below the plane of the ring.

    • Beta Linkage: O atom above the plane of the ring.

  • Enzymatic Activity: Human enzymes can hydrolyze alpha bonds but not beta bonds.

Polysaccharides

• Definition: Large macromolecules made from hundreds to thousands of monosaccharides.

• Types Based On:

  • The types of monomers present.

  • The position of glycosidic linkages.

  • The extent of branching.

Storage Polysaccharides

• Plants:

  • Starch: Composed of glucose; serves as energy storage.

• Animals:

  • Glycogen: Highly branched polymer of glucose stored in the liver and muscles.

Structural Polysaccharides

• Chitin: Found in arthropod exoskeletons, providing structural support.

Lipids

• Characteristics: Not polymers and generally not large enough to be classified as macromolecules.

• Hydrophobic Nature: Primarily composed of hydrocarbons, with some polar regions due to oxygen.

Fats

• Composition: Made of glycerol and fatty acids.

• Hydrophobic Properties: Generally hydrophobic due to hydrocarbon chains.

• Triglycerides Formation: Synthesized through dehydration reactions linking fatty acids to glycerol.

Variation in Fats

• Ester Linkages: Define variations in fats based on fatty acid tails.

Saturated vs. Unsaturated Fats

• Saturated Fats:

  • Structure: Do not contain C-C double bonds.

  • Physical State: Solid at room temperature due to tight packing.

• Unsaturated Fats:

  • Structure: Contain C-C double bonds, preventing close packing.

  • Physical State: Liquid at room temperature due to kinks in fatty acid chains.

Functionality of Fats

• Energy Storage: 1 g of fat contains more energy than 1 g of polysaccharide.

• Additional Functions: Protection, insulation, and energy storage.

Phospholipids

• Structure: Composed of two fatty acids, glycerol, and a phosphate group.

• Properties: Hydrophilic heads and hydrophobic tails define their membrane structure.

Phospholipid Structure

• Visual Representations: Different models including structural and space-filling models.

Phospholipids and Water Interaction

• Micelles and Membranes Formation: When mixed with water, phospholipids spontaneously arrange into micelles and membranes.

Steroids

• Structure: Composed of four fused rings.

• Components: Include cholesterol and steroid hormones (e.g., androgens, estrogens).

Common Steroids

• Examples: Structures of estradiol and testosterone, highlighting their functional groups.

Proteins

• Functionality: Most diverse molecules, performing numerous functions; dependent on their diverse forms.

• Production: Tens of thousands of proteins produced by human cells, each with a unique shape.

Protein Structure

• Composition: Polymers of amino acids (20 types).

• Common Structure: Each amino acid possesses an alpha carbon, an amino group, carboxyl group, and a variable side chain (R group).

Amino Acids and Their Types

• Classification: Side chains can be nonpolar (hydrophobic), polar, or electrically charged (hydrophilic).

  • Examples: Methionine, Glycine, Alanine, and Charged amino acids (Aspartic and Glutamic acid).

Peptide Bonds

• Formation: Amino acids are linked by peptide bonds, a process involving the removal of water (condensation reaction).

Protein Folding

• Structure Types: Proteins are folded into polypeptides; folding and structure are crucial to function.

• Sequence: The amino acid sequence drives the folding process.

Levels of Protein Structure

1. Primary Structure: Linear ordering of amino acids (e.g., transthyretin).

2. Secondary Structure: Includes α-helices and β-pleated sheets stabilized by hydrogen bonds.

3. Tertiary Structure: Involves various interactions, including hydrophobic interactions, hydrogen bonds, and ionic bonding.

4. Quaternary Structure: Multiple polypeptides forming functional proteins, exemplified by transthyretin.

Protein Denaturation

• Definition: Loss of protein structure under extreme conditions (heat, chemicals), leading to loss of function.

• Renaturation: Some proteins can return to functional shape when conditions become favorable again.

Nucleic Acids

• Polymers of Nucleotides: Comprised of a 5-carbon sugar, phosphate group, and nitrogenous base.

• Types:

  • DNA: Stores hereditary information, serves as a template for cellular activities.

  • RNA: Involved in decoding DNA and synthesizing proteins (e.g., mRNA).

Nitrogenous Bases

• Types:

  • Pyrimidines: Cytosine (C), Thymine (T in DNA), Uracil (U in RNA).

  • Purines: Adenine (A), Guanine (G).

DNA Structure

• Nucleotide Structure: Includes nitrogenous base, sugar (deoxyribose), and phosphate group.

• Nucleotide Linkage: Nucleotides are connected through phosphodiester bonds formed by condensation reactions.

• Double Stranded Structure: Antiparallel strands with a phosphodiester backbone and complementary base pairing (G:C and A:T).

• Stability: DNA forms a stable right-handed helix supported by hydrogen bonding and a robust backbone.

RNA Structure

• Flexibility: RNA can fold into complex shapes and is not confined to a rigid structure like DNA.

RNA vs DNA Comparison

• Differences in:

  • Sugar: DNA (deoxyribose) vs. RNA (ribose).

  • Strands: DNA (double-stranded) vs. RNA (typically single-stranded).

  • Bases: DNA (A, G, C, T) vs. RNA (A, G, C, U).

Overview of Biomolecules

• Monosaccharides: (e.g., glucose, fructose) serve as carbon sources.

• Disaccharides: (e.g., lactose, sucrose) serve as energy sources.

• Polysaccharides: (e.g., cellulose, starch, glycogen, chitin) serve structural and energy storage functions.

• Lipids: (e.g., triglycerides, phospholipids) form membranes and store energy.

• Proteins: (e.g., enzymes, structural proteins) perform numerous cellular functions.

• Nucleic Acids: (e.g., DNA, RNA) store and transfer genetic information.