Biochemistry

1. Organic vs. Inorganic Compounds

• Organic Compounds

  • Defined by the presence of carbon-hydrogen (C-H) bonds.

  • Often complex molecules, typically larger than inorganic compounds.

  • Examples: Carbohydrates, lipids, proteins, nucleic acids (all biological macromolecules).

  • Associated with living organisms or their products.

• Inorganic Compounds

  • Lack carbon-hydrogen bonds.

  • Generally simpler molecules.

  • Examples: Water ($H<em>2O$), salts (e.g., $NaCl$), acids (e.g., $HCl$), bases (e.g., $NaOH$), many gases (e.g., $CO</em>2$ (carbon dioxide, though it contains carbon, it is typically considered inorganic due to its simple structure and lack of C-H bonds)).

2. Dehydration Synthesis (Condensation Reaction)

• A process where two smaller molecules (monomers) are joined together to form a larger molecule (polymer).

• Involves the removal of a water molecule ($H_2O$).

• Typically, a hydroxyl group ($-OH$) is removed from one monomer and a hydrogen atom ($-H$) is removed from the other.

• This is how biological macromolecules (polymers) like polysaccharides, proteins, and nucleic acids are built from their respective monomers.

3. Hydrolysis

• The reverse of dehydration synthesis.

• A process where a large molecule (polymer) is broken down into two smaller molecules (monomers).

• Involves the addition of a water molecule ($H_2O$).

• The water molecule breaks into a hydroxyl group ($-OH$) and a hydrogen atom ($-H$), which then attach to the separate monomers.

• This is how biological macromolecules are broken down for energy or to reuse their components.

4. Carbohydrates

• Elements: Carbon (C), Hydrogen (H), Oxygen (O) in a ratio often approximating $(CH<em>2O)</em>n$.

• Monomers: Monosaccharides (simple sugars), e.g., glucose, fructose, galactose.

• Polymers: Polysaccharides, e.g., starch (plant energy storage), glycogen (animal energy storage), cellulose (plant structural), chitin (fungal cell walls, exoskeleton).

• Functions: Primary source of quick energy, structural components (cellulose in plants), cell recognition.

5. Lipids

• Elements: Primarily Carbon (C), Hydrogen (H), and some Oxygen (O).

• Characteristics: Hydrophobic (water-fearing), meaning they do not dissolve in water.

• Types and Functions:

  • Triglycerides: Composed of one glycerol and three fatty acid chains. Function: Long-term energy storage, insulation, cushioning.

  • Phospholipids: Composed of one glycerol, two fatty acid chains, and a phosphate group. Function: Major component of cell membranes (form bilayers).

  • Steroids: Characterized by a carbon skeleton consisting of four fused rings. Function: Hormones (e.g., testosterone, estrogen), cholesterol (membrane component, precursor to other steroids).

6. Proteins

• Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), often Sulfur (S).

• Monomers: Amino acids (20 different types).

• Structure: Determined by the specific sequence and folding of amino acids.

  • Primary: Linear sequence of amino acids.

  • Secondary: Local folding into $\alpha$-helices or $\beta$-pleated sheets.

  • Tertiary: Overall three-dimensional shape of a single polypeptide chain.

  • Quaternary: Arrangement of multiple polypeptide chains (subunits) in a protein.

• Functions: Enzymes (catalyze reactions), structural support (collagen, keratin), transport (hemoglobin), defense (antibodies), muscle contraction (actin, myosin), hormones (insulin).

7. Nucleic Acids

• Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P).

• Monomers: Nucleotides.

• Nucleotide Components:

  • A pentose sugar (deoxyribose in DNA, ribose in RNA).

  • A phosphate group.

  • A nitrogenous base (adenine, guanine, cytosine, thymine in DNA; adenine, guanine, cytosine, uracil in RNA).

• Types and Functions:

  • DNA (Deoxyribonucleic Acid): Usually double-stranded helix. Stores and transmits genetic information.

  • RNA (Ribonucleic Acid): Usually single-stranded. Involved in gene expression (e.g., mRNA, tRNA, rRNA).

8. pH Level

• Definition: A measure of the acidity or alkalinity (basicity) of a solution.

• Scale: Ranges from 0 to 14.

  • pH < 7: Acidic (higher concentration of $H^+$ ions).

  • $pH = 7$: Neutral (equal concentration of $H^+$ and $OH^-$ ions).

  • pH > 7: Basic or alkaline (higher concentration of $OH^-$ ions).

• Hydrogen Ions ($H^+$) and Hydroxide Ions ($OH^-$): The balance between these ions determines the pH.

• Buffers: Substances that resist changes in pH by accepting or donating $$