Chemistry Ionic and Covalent Bonds

Ionic Bonds: Involve the transfer of electrons; typically form between metals and nonmetals (e.g., NaCl); result in cations and anions attracting each other.
Covalent Bonds: Form through sharing of electrons; can be nonpolar (equal sharing, e.g., H-H) or polar (unequal sharing, e.g., H2O).
Hydrogen Bonds: Weak attractions between molecules; occur when a partial positive hydrogen atom interacts with electronegative atoms (F, O, N), prominent in water.

Water is a polar covalent molecule composed of two hydrogen atoms and one oxygen atom; oxygen carries a partial negative charge.
Its polarity allows water to dissolve many substances, making it the universal solvent.

pH indicates acidity or basicity based on hydrogen ion concentration; higher H+ concentration means more acidic, while lower H+ concentration means more basic.
Key body fluids like spinal fluid, blood, saliva, and water generally have a neutral pH around 7.

Enzymes accelerate chemical reactions without being consumed by lowering the activation energy required for the reaction.
They bind to substrates (often amino acids) and can be reused in subsequent reactions.

Carbon, with six protons, neutrons, and electrons, is stable and forms long chains (C-C bonds), essential for organic compounds.
Carbon's ability to form single, double, or triple bonds is key to its versatility in biological molecules.

Lipids: Include fatty acids, triglycerides, and phospholipids; have hydrophilic heads and hydrophobic tails; essential in cell membranes, hormone synthesis, and signaling.
Carbohydrates: Provide glucose and energy, are polar and hydrophilic; structured as CH2O.
Nucleic Acids: DNA and RNA, responsible for genetic information; DNA is double-stranded, RNA is single-stranded.
Proteins: Composed of amino acids; vital for tissue repair, enzyme activity, cellular communication, and immune defense.

ATP consists of adenine, ribose sugar, and three phosphate groups; high-energy bonds release energy upon phosphorylation.
Powers cellular activities, including molecule transport across membranes.

Comprised of a phospholipid bilayer that regulates substance passage; phospholipids have outward-facing hydrophilic heads and inward-facing hydrophobic tails.
Contains transmembrane proteins for molecule entry and cholesterol for membrane rigidity, along with carbohydrates (glycocalyx) for cell recognition.

Transport Proteins: Form channels or pumps to move substances across the membrane.
Anchor Proteins: Secure the cell by attaching the membrane to the cytoskeleton.
Receptor Proteins: Bind signals from other cells, triggering a response (e.g., hormones).
Cell-Cell Junction Proteins: Facilitate binding between adjacent cells.
Membrane Enzymes: Catalyze reactions on the cell surface.
Recognition Proteins: Help immune cells distinguish between self and foreign agents.

The cell membrane is selectively permeable, controlling material intake and providing structural flexibility for protein movement.
Organizes compartments within the cell through cytoplasm and cytoskeleton.

Isotonic: Equal solute and water concentration inside and outside the cell; no change in cell shape.
Hypotonic: Lower solute concentration outside the cell; water enters, potentially causing lysis (bursting).
Hypertonic: Higher solute concentration outside the cell; water leaves, leading to cell shrinkage.