Chemistry of Life: Properties and Structure of Biological Molecules

Composition: Water is composed of 2 Hydrogen (H) and 1 Oxygen (O).
Covalent Bonds: Atoms share electrons (as seen in water).
Polarity: Oxygen is more electronegative than hydrogen, leading to unequal electron sharing in water molecules, resulting in polarity.
Hydrogen Bonds: Weak bond interactions occur between negative (from Oxygen) and positive (from Hydrogen) regions of separate molecules.

Cohesion: Attraction between similar molecules (water-water interaction).
Adhesion: Attraction between different molecules (water-surface interactions).
Surface Tension: Hydrogen bonding causes surface tension, allowing water droplets to form shapes on surfaces.

Surface Tension: Increased hydrogen bonding forces at the surface create tension (e.g., water droplet on a penny).
High Solvency: Water is not a universal solvent but has high solvency for many substances.
Density of Ice: Water’s cohesive property allows ice to be less dense than liquid water, causing it to float.
High Heat Capacity: Water absorbs significant heat before changing states, resisting sudden temperature changes.
Capillary Action: Plants absorb water through both adhesion and cohesion, allowing movement through roots.
Energy Requirement: Living systems require a constant energy input for growth and organization.
Law of Conservation of Energy: Energy cannot be created or destroyed but can be transformed.
Importance of Carbon: Carbon forms the backbone of complex molecules, allows the creation of energy-storing molecules, and is essential in building cellular structures.

Role of Nitrogen and Phosphorus: Nitrogen builds proteins/nucleic acids; Phosphorus is essential for nucleic acids/lipids.
Monomers and Polymers: Monomers (building blocks) combine to form specific polymers through covalent bonding.
Dehydration Synthesis: Water is a byproduct of this reaction, allowing the formation of macromolecules (e.g., carbohydrates, proteins).

Formation of Macromolecules: Monomers lose H and OH to bond covalently, forming larger carbohydrates.

Breaking Down Polymers: Hydrolysis reactions cleave polymers into monomers by adding water to break covalent bonds.
Result of Hydrolysis: Separates polymers into individual monomers for proteins, releasing H and OH from water molecules to the respective amino acids.

Nucleic Acids: Polymers of nucleotides that store biological information.
Structure of Nucleotides: Consists of a 5-carbon sugar, phosphate group, and nitrogen base.
Types of Nucleic Acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) differ in sugar and nitrogen base composition.
Amino Acids: The monomers making up proteins have directionality (amino terminus to carboxyl terminus).

Directionality: Characterized by 5’ phosphate and 3’ hydroxyl ends.
DNA Structure: Anti-parallel strands with nucleotides pairing (Adenine-Thymine with 2 bonds, Guanine-Cytosine with 3 bonds).
Functional Implications: Sequence of nucleotides encodes biological information, and changes can affect function.

Primary Structure: Sequence of amino acids (held by peptide bonds).
Secondary Structure: Folding into structures like alpha-helices and beta-sheets.
Tertiary Structure: Overall 3D structure, stabilized by various bonds.
Quaternary Structure: Interactions between multiple polypeptide chains (e.g., hemoglobin).

Structure and Functional Diversity: Made of sugar monomers with linear or branched chains affecting function (e.g., starch, glycogen for energy; cellulose for plant structure).

Similarities: Both consist of 5-carbon sugars, phosphate groups, and nucleotides connected by covalent bonds (5’ to 3’).
Differences:
- Sugar Type: DNA (deoxyribose) vs. RNA (ribose).
- Nitrogenous Bases: DNA has thymine (T), RNA has uracil (U), both have adenine (A), guanine (G), and cytosine (C).
- Strands: DNA is double-stranded; RNA is single-stranded.
- Orientation: DNA strands are anti-parallel.