1. A 1.1 SL Water

A 1.1 – Water

• Essential for Life

  • What physical and chemical properties of water make it essential for life?

  • Challenges and opportunities of water as a habitat.

A1.1.1 Water as the Medium for Life

• The first cells originated in water; it is the medium for most life processes.

• Polarity in water molecules results from unequal sharing of electrons.

• Hydrogen bonding occurs between water molecules due to polarity, leading to various interactions essential for life.

A1.1.2 Hydrogen Bonds

• Represent the interactions between water molecules.

• Hydrogen bonds form due to polar covalent bonds, stabilizing water's structure and properties

  • Notation: Polarization indicated when drawing water molecules.

A1.1.3 Cohesion and Tension in Water

• Hydrogen bonding creates cohesion; contributes to water transport in xylem and surfaces as habitats (e.g., surface tension).

• Transport in Plants: Water moves under tension in xylem due to cohesive forces.

• Habitat Creation: Surface tension allows organisms to utilize water surfaces.

A1.1.4 Adhesion Properties

• Water adheres to polar or charged materials, affecting organisms.

• Capillary Action: Demonstrated in plant cell walls and soil; allows water movement in narrow spaces.

A1.1.5 Solvent Properties of Water

• Water dissolves many hydrophilic molecules.

• Enzymes catalyze reactions in an aqueous environment.

• Importance of hydrophobic molecules: Some cell functions depend on insoluble materials.

A1.1.6 Physical Properties of Water

• Buoyancy, Viscosity, Thermal Conductivity, Specific Heat: Essential for aquatic animals like the black-throated loon (Gavia arctica) and ringed seal (Pusa hispida).

• Physical properties create unique environments favoring certain adaptations in organisms.

Water Originated in Life

• Water allowed the first cells to develop membrane-enclosed spaces for essential reactions.

• Interaction of molecules in water underpins life processes.

Earth's Water Distribution

• Over 70% of Earth's surface is covered by water, primarily in oceans, contributing to life forms.

Importance of Water in Cells

• Water comprises cytoplasm, where metabolic reactions happen—enzymes depend on molecular interactions facilitated by water.

• Water as a fluid compartment: It aids cellular transport and maintains metabolic stability.

Evolution of Cells and Water Environments

• Early cells evolved membranes to maintain cytoplasmic separation from ocean water.

• Cell structures are primarily aquaeous; optimal chemical reactions occur in watery environments.

Polar Covalent Bonds and Water Structure

• Water molecules possess polar covalent bonds due to electron distribution; leads to hydrogen bond formation.

  • Electrostatic interactions generate partial charges (δ+ on H, δ- on O).

Drawing Water Molecule Structures

• Illustrate water molecule structure to highlight electrons and covalent bonds.

• Concepts of hydrogen bonds depicted through molecule interactions.

Multiple Water Molecules Representation

• Illustrate interactions demonstrating weak hydrogen bonds forming between partial charges of water molecules.

Biological Properties of Water

• Cohesion and adhesion lead to water's functional roles in ecosystems, explaining habitat dynamics.

Surface Tension Formation in Water

• Surface tension arises from cohesive forces caused by hydrogen bonding, enabling droplet formation.

Habitats Supported by Surface Tension

• Surface tension strong enough to support small insects; allows organisms like pond skaters and mosquito larvae to thrive.

Water Transport in Plants

• Water's cohesion allows upward movement under tension, crucial in the process of transpiration.

Adhesion Effect on Water Movement

• Attraction between polar water molecules and surfaces leads to movement in narrow tubes (capillary action).

• Water spreads through narrow spaces, critical for plant water uptake.

Resurrection Plants and Capillary Action

• Example of the rose of Jericho utilizes capillary action for rapid hydration during rehydration events.

Solvent Properties of Water

• Water's polarity attracts ions, facilitating dissolution of ionic compounds like NaCl.

• Key to metabolic reactions—enzyme activity in aqueous solutions.

Importance of Hydrophilic and Hydrophobic Molecules

• solution dynamics

• Polar (hydrophilic) molecules essential for life processes, while nonpolar (hydrophobic) substances require special transport mechanisms like lipoproteins.

Specific Cases of Molecule Solubility

• Examples include glucose, amino acids, and fats emphasizing polar interactions and transport mechanisms through blood plasma.

Physical Properties of Water

• Buoyancy: Provides an insulation layer (ice) assisting winter survival.

• Viscosity: Crucial for how organisms move through water; impacts swimming and energy expenditure.

• Thermal Conductivity and Specific Heat: Vital for maintaining stable aquatic habitats amidst temperature fluctuations.

Comparison of Air and Water Properties

• Significant differences in properties affect living adaptations in animal species.

• Case Study: Ringed seal vs. black-throated loon adaptations to buoyancy, viscosity, thermal conductivity, and specific heat.