SE Unit 1 Topic 4 5 and 6 Notes- Macromolecules

Biological Macromolecules: Properties, Structures, and Functions

Unit I: Topics 4, 5g, and 6 Overview

• This section provides foundational knowledge on the major classes of biological macromolecules including carbohydrates, proteins, nucleic acids, and lipids, focusing on their structures and functions.

Understanding Living Systems

Enduring Understanding: SYI-1

• Living systems exhibit complex organization in a hierarchical structure that interacts across various levels.

Learning Objectives: Key Knowledge

• SYI-1.B: Describes the properties of lipids as nonpolar macromolecules.

• SYI-1.B.2: Discusses how the structure and function of polymers relate to the arrangement and bonding of their monomers.

Lipids

• Lipids are primarily hydrophobic molecules.

• Their structural properties (saturation levels) influence their interactions and functions in biological systems.

• Phospholipids feature both polar and nonpolar regions, allowing interactions with water and other polar molecules.

Nucleic Acids

• Information is encoded in the sequences of nucleotides comprising nucleic acids (DNA, RNA).

• A nucleotide consists of three components: a five-carbon sugar, a phosphate group, and a nitrogenous base. Different organisms may have variations of these structures, e.g., DNA has deoxyribose while RNA has ribose.

Proteins

• The order of amino acids in a polypeptide chain is critical for determining protein structure and function.

• Amino acids vary by their side chain (R group) properties (hydrophobic, hydrophilic, ionic). Stability and structure are influenced by these side chain interactions.

Carbohydrates

• Carbohydrates consist of sugar monomers whose structures dictate their biological roles and properties.

Detailed Structures of Biological Macromolecules

Proteins

• Formation: From amino acids to polypeptides to functional proteins.

• Comprised of: C, H, O, N, S. The three-dimensional shape is pivotal for function.

Amino Acids and Their Role

• Amino acids contain common groups: an amino group, a carboxyl group, and a variable side chain (R).

• There are 20 different amino acids, categorized based on their properties. The interactions among these side chains are crucial for the protein's final structure and function.

Formation of Peptide Bonds

• Peptide bonds form between the carboxyl group of one amino acid and the amino group of another through dehydration reactions, linking them into polypeptides.

Levels of Protein Structure

1. Primary Structure: Sequence of amino acids.

2. Secondary Structure: Local folding into structures like alpha-helices and beta-sheets.

3. Tertiary Structure: Overall three-dimensional structure, determined by interactions among R groups.

4. Quaternary Structure: Arrangement of multiple polypeptide subunits.

Functions of Proteins

• Proteins play various roles, including:

• Antibodies (immune response)

• Enzymes (catalyzing reactions)

• Hormones (cell signaling)

• Structural components (support)

• Transport/storage molecules.

Nucleic Acids

• Serve as polymers of nucleotide monomers, crucial for the storage and transmission of hereditary information.

• DNA and RNA share components but vary in structure and function.

• DNA is typically double-stranded with deoxyribose and thymine; RNA is mostly single-stranded, containing ribose and uracil.

Components of Nucleic Acids

• Nucleotides: Composed of a nitrogenous base, a five-carbon sugar, and a phosphate group.

• Polynucleotides: Formed through phosphodiester linkages linking nucleotides, they have directionality from the 5’ phosphate to the 3’ hydroxyl end.

Structure of DNA

• Comprises two polynucleotide strands forming a double helix, with specific base pairing rules: A-T and C-G.

Structure of RNA

• Typically a single-stranded molecule, with potential base pairings happening within the strand.

Carbohydrates

• Include simple sugars and complex polysaccharides, essential biological molecules with a carbonyl group and multiple hydroxyl groups.

• Monosaccharides: Simple sugar units like glucose, serving fundamental roles in energy provision and metabolism.

• Disaccharides: Formed from two monosaccharides, with sucrose as a prime example.

• Polysaccharides: Complex carbohydrates like starch (storage in plants) and glycogen (storage in animals); structural polysaccharides include cellulose and chitin.

Lipids

• Lipids differ from other macromolecules, often not forming true polymers. They are predominantly hydrophobic.

  • Fats: Composed of glycerol and fatty acids; can be saturated or unsaturated based on carbon-carbon bonding.

  • Phospholipids: Integral to cell membranes, consisting of hydrophobic tails and a hydrophilic head, forming bilayers in aqueous environments.

  • Steroids: Characterized by fused ring structures, with varying functional groups modifying their properties (e.g., testosterone).

Summary Chart

This comprehensive study of biological macromolecules covers their properties, structures, and functions, which are fundamental for understanding life at a molecular level.