Biology Chapter on Water Functions

Water (H₂O)

• Composes 60% to 80% of body cells, serving as a crucial solvent and medium for biological reactions.
• Functions include transporting materials, regulating body temperature through heat absorption/release, and acting as a lubricant.
• Exhibits polarity, with a slight negative charge on the oxygen side and a slight positive charge on the hydrogen side, attracting charged molecules (hydrophilic).
• Hydrophilic molecules mix well with water, while hydrophobic molecules (like fats) do not.
• Hydrogen bonds stabilize water's structure, enhancing its heat capacity; water heats and cools slower than air.
• Ice is less dense than liquid water, causing it to float.

Enzymes

• Proteins that accelerate chemical reactions in cells, vital for biological molecule breakdown and synthesis.
• Enzymes only interact with specific substrates, which are reactants in enzyme-catalyzed reactions.

Cellular Respiration and ATP

• In mitochondria, glucose and oxygen convert into ATP (adenosine triphosphate), the energy currency of the cell.
• ATP consists of a base, sugar, and three high-energy phosphate groups; breaking these bonds releases energy.
• When ATP releases energy, it converts to ADP (adenosine diphosphate) which can be recharged by gaining another phosphate.

Overview of Cells

• Cells are the fundamental units of life, varying in shape and size based on function (e.g., nerve, blood, muscle cells).
• Common traits of cells include a nucleus (except mature red blood cells), cell membrane, organelles, and cytoplasm.

Cell Membrane

• Composed largely of a phospholipid bilayer, which prevents hydrophilic substances from crossing.
• Contains cholesterol for stability and proteins facilitating selective permeability.
• Essential for transporting waste like carbon dioxide to the lungs.

Osmosis

• A specific type of passive transport where water moves through a selectively permeable membrane from low to high solute concentration.
• Osmotic pressure refers to the force that pulls water towards higher solute concentrations.
• Tonicity describes solute concentration: hypertonic (outside higher solute), hypotonic (inside higher solute), isotonic (equal solute levels).
• Crenation occurs when cells lose water in a hypertonic solution, while hypotonic solutions can cause cells to burst from excess water intake.

Stem Cells and Regenerative Medicine

• Stem cells can divide and form new tissues, aiding in internal repair mechanisms.
• They are derived from adult and embryonic sources, with induced pluripotent stem cells representing a recent advancement.
• Regenerative medicine explores the potential to grow tissues and organs for replacements.

Body Systems

• Eleven major systems interact to perform complex functions:
  • Skeletal: Support, protection, and mineral storage.
  • Muscular: Voluntary and involuntary muscle groups facilitating movement.
  • Integumentary: Skin provides protection, temperature regulation, and sensation.
  • Gastrointestinal: Breaks down food, absorbs nutrients, and eliminates waste.
  • Urinary: Eliminates waste and regulates water and electrolyte balance.
  • Reproductive: Facilitates reproduction and includes male and female organs.

Key Concepts

• Cells are the basic building blocks of life, forming tissues, which are composed of similar cell types.
• Membranes are sheet-like structures with specific functions, including cutaneous, serous, mucous, and synovial types.
• Organs consist of tissues that serve specific functions, and systems consist of organs working together for broader functions.

Explore the essential roles of water in the human body through this quiz. Understand how water contributes to cellular composition, serves as a solvent, and regulates body temperature. Test your knowledge about the importance of hydration and acid elimination.