Biochemistry: Ions and Polar Molecules

Ion and Polar Molecules

• Ions and polar molecules have electrical or partial charges, making them hydrophilic (water-loving).
• Water (H2O) comprises over 60% of the body, featuring polar characteristics with a partial negative charge on oxygen and partial positive charges on hydrogens.
• In an aqueous solution, ions are surrounded by a shell of water molecules, facilitating solubility.

Polar and Nonpolar Biomolecules

• Polar biomolecules like monosaccharides, amino acids, and nucleotides contain C-O, O-H, and N-H bonds, contributing to their hydrophilicity.
• Lipids are primarily nonpolar, consisting of carbon-hydrogen bonds, and are classified as hydrophobic (water-hating) due to their inability to form hydrogen bonds with water.

Cell Membrane Composition

• The cell membrane's hydrophobic core is comprised of lipid layers, fatty acid tails, and cholesterol, essential for separating intracellular and extracellular fluids.
• Nonpolar molecules, including many medications, can easily pass through the lipid environment of the membrane, while polar or charged molecules like glucose and amino acids require transport mechanisms.

Membrane Transport

• Hydrophilic substances need specialized membrane transport proteins for crossing the cell membrane, which are important drug targets.
• Blood glucose stabilization involves the conversion of glucose to glycogen, a reversible process occurring in the liver and muscles, regulating energy during fasting and eating.

Role of Fatty Acids and Amino Acids

• Arachidonic acid is released from membrane phospholipids, serving as a precursor to inflammatory mediators such as prostaglandins and leukotrienes, involved in acute and allergic responses.
• Understanding amino acid classifications (hydrophobic/hydrophilic, neutral/polar/charged) is key to grasping the impact of mutations on physiology.

Genetic Mutations and Sickle Cell Disease

• Genetic mutations affecting single amino acids can lead to diseases, exemplified by sickle cell disease, caused by replacing glutamate with valine in hemoglobin.
• Knowledge of amino acid properties is vital for comprehending the connections between mutations and physiological outcomes.

Phosphorylation and Signal Transduction

• Hydroxyl-containing amino acids like serine, threonine, and tyrosine are phosphorylation sites that regulate cellular activity in response to second messengers.
• Tyrosine kinases, which phosphorylate tyrosines, are significant in cancer pathology and treatment, highlighting the need for understanding these enzymes.

Nucleotide Functions

• ATP and GTP function as primary energy sources, fueling cell processes and signaling, respectively.
• Nucleotides can transition to cyclic forms (cAMP and cGMP) to act as intracellular second messengers involved in various signaling pathways.

Cell Death and Energy Production

• Ischemia, such as in myocardial infarction or stroke, leads to ATP production failure, marking a critical pathway of cell death.
• DNA and RNA, as polymers of nucleotides, are foundational to molecular biology, with complementary base-pairing ensuring accurate genetic information transmission.