Notas sobre pH, agua y carbono

• These are study notes about different chemical processes and biological molecules

Acidity and Basicity

• pH measures the acidity or basicity of a liquid solution on a scale from 0-14
• The pH scale is vital for living organisms because many chemical reactions and biological processes work within an optimal pH range
• A buffer solution consists of a weak acid and its conjugate base (or a weak base and its conjugate acid)
• Buffers maintain a solution's pH within a specific range, preventing significant changes and maintaining homeostasis

Water's Properties and Importance

• Water is seen as a universal solvent because of its polarity, enabling it to dissolve many substances (polar substances and those forming hydrogen bonds)
• Water acts as a universal solvent (for polar and ionic substances)
• Water helps in transport, acts as a medium for chemical reactions, and shows diverse behavior as a nucleophile, electrophile, acid, or base

Carbon's Role in Life

• Carbon is crucial for life
• Carbon forms stable structures as the base of organic molecules
• Carbon can form cyclic, branched, and linear structures

Biomolecules

• The four main biomolecules are carbohydrates, lipids, proteins, and nucleic acids
• Carbohydrates function as fuel, provide energy, and help in cell signaling
• Lipids store long-term energy and build cell membranes
• Proteins have various functions, including enzymatic activity, protection, structural support, and signaling
• Nucleic acids store genetic information and help in protein synthesis

Amphipathic Molecules

• Amphipathic molecules have both polar (hydrophilic) and nonpolar (hydrophobic) parts
• This structure makes them form micelles and membranes
• The structure allows the transportation of nonpolar molecules and maintains cellular equilibrium (homeostasis)

Hydrolysis

• Hydrolysis is a chemical reaction where a large molecule breaks down into smaller ones using water
• It is essential for breaking down lipids and proteins

Micelles

• Micelles are sphere-shaped structures made of amphiphilic molecules
• Micelles transport nonpolar substances in aqueous environments

Oxygen and Carbon Dioxide

• Oxygen (O₂) and carbon dioxide (CO₂) have limited solubility because they are nonpolar and so they cannot form hydrogen bonds with water
• To compensate, organisms use specialized proteins to transport and store oxygen and carbon dioxide (hemoglobin)

Bond Valence

• Bond valence refers to the charge of an ion, indicating the number of electrons available for bonding
• Monovalent ions have a charge of +1 or -1
• Divalent ions have a charge of +2 or -2

Ion Solubility

• Monovalent ions are more soluble in water because they have a lower charge and separate with less force
• Divalent ions are less soluble in water because they have a higher charge and attract each other with more force

pKa

• pKa measures the strength of an acid, indicating how easily it releases hydrogen ions (H+)
• A low pKa means a strong acid that releases H+ easily
• A high pKa means a weak acid that does not release H+ easily

pH and pKa Relationship

• If pH < pKa the medium is more acidic than the acid itself
• The acid will mostly remain in its protonated form, not releasing many protons
• If pH = pKa the medium and the acid have the same level of acidity – the acid is 50% dissociated
• If pH > pKa the medium is more basic than the acid, and it will dissociate completely and take on its deprotonated form

Van der Waals Interactions

• Van der Waals interactions are weak forces present in abundance
• The Van der Waals interactions do not require the exchange of electrons or ions
• Van der Waals interactions include dipole-dipole (between polar molecules), dipole-induced dipole (between a polar and a nonpolar molecule), and induced dipole-induced dipole (between nonpolar molecules) interactions

Types of Bonds

• Ionic bonds are very strong and involve the transfer of electrons
• Hydrogen bonds are moderately strong (between hydrogen, a highly electronegative atom, and another with free electrons)
• Van der Waals interactions are weak and occur individually

Entropy and Solubility

• Systems favor processes that increase entropy (disorder)
• Nonpolar molecules do not dissolve well in water, which orders the water molecules around them, decreasing entropy, and thus have low solubility
• Polar molecules dissolve well, which disperses the molecules and increases entropy, and thus have high solubility