Biomolécules UE 2.1: L'eau et ses liens

Introduction

• The presentation is about biological molecules, specifically focusing on water molecules and their role in the human body.
• The unit (UE) number is 2.1, indicating it's part of a larger curriculum.
• The presenter is Caroline Schmitt, from the Biochemistry department and INSERM U1149, affiliated with CHU Louis Mourier.

Types of Chemical Bonds

• Strong bonds: Covalent bonds require a substantial amount of energy to break them and maintain the rigid structure of biomolecules.

• Weak bonds: Non-covalent bonds (hydrogen bonds, ionic interactions, and hydrophobic interactions) have a lower energy of interaction (10 to 100 times less than covalent bonds).

Water Molecule

• Chemical Formula: H₂O
• Structure: Two hydrogen atoms covalently bonded to one oxygen atom.
• Polarity: Water is a polar molecule due to the electronegativity difference between oxygen and hydrogen atoms. This creates a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. The uneven distribution of charges makes water attractive to other molecules.

Water Properties

• Solvent properties: Water acts as a universal solvent because it dissolves various substances, and through interactions with the solutes this process (hydration) occurs.

Water in the Body

• Abundance: Water constitutes a significant portion of living matter (55-65% in adults).
• Distribution: Approximately 2/3 of the water is intracellular, while 1/3 is extracellular, including plasma and lymph.
• Water Balance: Daily water intake and output (urine, feces, sweat, and exhalation) need to be balanced.
• Age variability: Water percentage varies based on age (higher in infants).
• Tissue variability: Different tissues have different water content (like muscle and bone).
• Roles in the organism:
  • Hydration.
  • Nutrient distribution.
  • Participation in hydrolysis reactions.
  • Waste removal.

Osmosis

• Definition: A physical process where water moves from an area of lower solute concentration to an area of higher solute concentration across a semipermeable membrane. This process occurs until an equilibrium of concentration between compartments (isotonicity) is reached.

Practical Examples

• Isotonic Solutions: Crucial for intravenous fluids (e.g., saline solutions (0.9% NaCl) and glucose solutions (5% glucose). These solutions have osmotic pressure that matches that of blood plasma to prevent cell shrinking or swelling.
• Dehydration: A significant decrease in body water can lead to severe consequences (e.g., shock). Symptoms include loss in skin turgor, decreased urine output, sunken eyes etc... and the loss of 3% of water can result in thirst, while the loss of 20% can be fatal.

Presentation Details

• Includes graphic elements.
• Uses diagrams to illustrate concepts like water molecules and osmosis.