Water, pH, and Buffers in Life Science

Water, pH, and Buffers

• Water is essential for life, serving as the medium for life processes.
• Earth's surface is approximately 73% covered by water, and all living things rely on it.
• The human body is comprised of over 70% water, a key component of bodily fluids (e.g., blood, urine, saliva).
• Water plays a vital role in the chemistry of life; almost all chemical reactions happen in an aqueous environment.
• Water dissolves nutrients, making them easily transportable.
• Proteins, polysaccharides, nucleic acids, and membranes adopt specific shapes in response to water's properties.
• Water's chemical properties are directly linked to the functions of biomolecules, entire cells, and organisms.
• Water possesses two crucial properties: physical and chemical.

Physical Properties

• Water is a polar molecule.
• Two hydrogen atoms covalently bond with one oxygen atom.
• This creates an asymmetrical distribution of charge; one side is partially positive, and the other is partially negative.
• Due to this polarity, water is a good solvent for many substances.

Hydrogen Bonds

• Water's unusual properties arise from hydrogen bonds between water molecules and between water and polar solutes.
• Each water molecule forms four hydrogen bonds.
• This explains water's high boiling point, melting point, and surface tension.

Water as a Solvent

• Water is an excellent solvent, dissolving a wide range of organic and inorganic molecules.
• Hydrophilic ("water-loving") compounds readily dissolve in water, while hydrophobic ("water-fearing") compounds (e.g., lipids, waxes) do not.
• This relates to the functions of biomolecules, entire cells, and organisms.

Osmosis

• Osmosis is the movement of water across a semipermeable membrane from a region of higher water concentration to one with lower water concentration.
• Maintaining proper hydration is vital for proper bodily function.

Isotonic, Hypotonic, and Hypertonic Solutions

• Isotonic solutions have the same osmotic pressure as blood.
• Hypotonic solutions have lower osmotic pressure than blood.
• Hypertonic solutions have higher osmotic pressure than blood.

Chemical Properties (Ionization)

• Water slightly ionizes into hydrogen ions (H+) and hydroxide ions (OH−).
• At 25°C, the concentrations of H+ and OH− are equal (1 × 10−7 M).
• The concentration of water is a constant (55.5 M).

pH

• pH is a shorthand measure of the concentration of hydrogen ions (H+) in a solution.
• The pH scale is logarithmic (inverse logarithm), ranging from 0 to 14.
• pH values below 7 are acidic, and those above 7 are basic.
• pH values in cells and blood are close to neutral; extreme values are generally detrimental.

Acid

• An acid increases the concentration of hydrogen ions (H+) in a solution, often by releasing hydrogen atoms.
• Acids are proton donors.

Strong and Weak Acids

• Some acids completely ionize (strong acids) while others do not (weak acids).
• Strong acids undergo irreversible reactions, while weak acids are reversible.

Base

• A base increases the concentration of hydroxide ions (OH−) in a solution or reduces hydrogen ions (H+).
• Bases are proton acceptors or hydroxide donors.

Strong and Weak Bases

• Strong bases completely dissociate into ions.
• Weak bases do not fully ionize.

Ionization Constants of Acids (Ka)

• Ka measures an acid's ability to dissociate.
• Strong acids have high Ka values and dissociate completely in water.
• Weak acids have low Ka values and only partially dissociate.

Physiological pH

• It's crucial to maintain a stable pH within the human body.
• This is achieved by the use of buffers.
• Inside cells, the pH is roughly 7, and for blood it is 7.4 ± 0.05.

Buffers

• Buffers are solutions of a weak acid and its conjugate base, or a weak base and its conjugate acid.
• They resist changes in pH by absorbing excess H+ or OH-.
• Buffers facilitate body stability, preventing large pH fluctuations.

Buffer Systems in the Body

• Proteins are the body's primary intracellular buffers.

• Phosphate buffers are primarily found within cells.

• Carbonic acid(H₂CO₃), bicarbonate(HCO₃⁻) and carbon dioxide (CO₂) act as critical buffers in the blood.

• Maintaining constant blood pH is necessary for proper bodily functions.

• The buffering system in blood prevents drastic fluctuations.

Explore the fundamental role of water in biological systems through this quiz. Understand how water's physical and chemical properties influence life processes, nutrient transport, and biomolecular structures. Test your knowledge on the importance of pH and buffers in maintaining life's chemistry.