Ch. 2: The Chemical Level of Organization – Study Notes

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Inorganic compounds are essential to life and include water, salts, acids, and bases. They generally do not contain carbon-hydrogen bonds.

Water
- High heat capacity: Water can absorb and release large amounts of heat with little temperature change, helping to stabilize body temperature.
- High heat of vaporization: A significant amount of energy is required to convert water from liquid to gas, which is important for cooling the body through perspiration.
- Polar solvent properties: Water's polarity makes it an excellent solvent, allowing it to dissolve and transport many substances in the body.
- Reactivity: Water is involved in many chemical reactions, including hydrolysis and dehydration synthesis.
- Cushioning: Water provides protection to organs by forming a cushion (e.g., cerebrospinal fluid around the brain).
Electrolytes
- Salts: Ionic compounds that dissociate in water to form ions, which are essential for nerve impulse transmission and muscle contraction.
- Acids: Substances that release hydrogen ions (H+) in solution. Example: Hydrochloric acid (HCl) in the stomach.
- Bases: Substances that accept hydrogen ions or release hydroxide ions (OH-). Example: Bicarbonate ion (HCO3-) in blood.

Organic compounds contain carbon and are the building blocks of life. They include carbohydrates, lipids, proteins, and nucleic acids.

Macromolecules: Making and Breaking
- Dehydration synthesis: The process by which monomers are joined to form polymers, releasing water as a byproduct.
- Hydrolysis: The process by which polymers are broken down into monomers by the addition of water.

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as a primary energy source for the body.

Monosaccharides: Simple sugars with a single ring structure.
- Hexose sugars (6 carbons): Glucose, Fructose, Galactose
- Pentose sugars (5 carbons): Deoxyribose (in DNA), Ribose (in RNA)
Disaccharides: Formed by joining two monosaccharides via dehydration synthesis.
- Glucose + Fructose → Sucrose
- Glucose + Glucose → Maltose
- Glucose + Galactose → Lactose
Polysaccharides: Long chains of monosaccharides; used for energy storage.
- Starch: Storage form of glucose in plants.
- Glycogen: Storage form of glucose in animals, mainly in liver and muscle cells.

Lipids are hydrophobic organic molecules that serve as energy storage, structural components, and signaling molecules.

Triglycerides: Composed of glycerol and three fatty acids; main form of stored energy in the body.
Phospholipids: Contain a phosphate group; major component of cell membranes.
Steroids: Four-ring structure; includes cholesterol, which is a precursor for steroid hormones.
Eicosanoids: Derived from arachidonic acid; involved in inflammation and cell signaling.

Proteins are polymers of amino acids linked by peptide bonds. They perform a vast array of functions in the body.

Amino acid monomers: Linked by peptide bonds to form polypeptides and proteins.
Structure determines function: The specific sequence and shape of a protein determine its role (e.g., enzymes, structural proteins, hormones).
Enzymes: Proteins that act as biological catalysts, lowering the activation energy of chemical reactions.

Nucleic acids store and transmit genetic information. They include DNA, RNA, and ATP.

DNA (Deoxyribonucleic acid): Stores genetic information; double helix structure.
RNA (Ribonucleic acid): Involved in protein synthesis; single-stranded.
ATP (Adenosine triphosphate): The primary energy carrier in cells.
- Uses of ATP: Provides energy for cellular processes such as muscle contraction, active transport, and biosynthesis.