Cellular Level

Introduction to Matter and Atomic Structure

Definitions:

  • Matter: Anything that occupies space and has mass, composed of elements.

  • Atom: The building block of all matter.

  • Element: A pure substance composed of atoms; 96% of the body consists of Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Atomic Structure:

  • Nucleus (Core): Contains protons (+ charge) and neutrons (neutral).

  • Electron Cloud: Contains electrons (- charge), orbiting in shells.

  • Atomic Number: Number of protons (identifies the element).

  • Mass Number: Protons + Neutrons.

  • Isotope: Same element, different neutron number (affects mass).

  • Valence Electrons: Outermost shell electrons involved in bonding.

  • Octet Rule: Atoms tend to bond to achieve 8 valence electrons.

Chemical Bonds and Molecules

Definitions:

  • Molecule: Two or more atoms chemically bonded (e.g., O₂, H₂O).

  • Compound: A molecule composed of different elements (e.g., NaCl).

Types of Bonds:

  1. Ionic Bonds:

    • Involves electron transfer, forming ions.

    • Cation: Loses electrons, becomes positively charged.

    • Anion: Gains electrons, becomes negatively charged.

    • Weak in fluids; dissociate easily.

  2. Covalent Bonds:

    • Involves electron sharing.

    • Non-Polar Covalent: Equal sharing.

    • Polar Covalent: Unequal sharing (e.g., water).

    • Strong bonds.

  3. Hydrogen Bonds:

    • Weak attraction between polar molecules.

    • Creates cohesion in water molecules.

Chemical Reactions

Types of Reactions:

  1. Synthesis (Anabolism): Combining molecules to form a larger molecule.

  2. Decomposition (Catabolism): Breaking down large molecules into smaller ones.

  3. Oxidation-Reduction (Redox):

    • Oxidation: Loss of electrons.

    • Reduction: Gain of electrons.

Factors Affecting Reaction Rates:

  • Temperature

  • Particle size

  • Reactant concentration

  • Presence of catalysts (enzymes)

Biochemistry: Inorganic Molecules

Water:

  • Universal solvent.

  • High heat capacity & heat of vaporization.

  • Reactant in hydrolysis & dehydration synthesis.

Salts:

  • Dissociate into electrolytes (ions).

  • Important for nerve impulses & muscle contractions.

Acids, Bases, and Buffer Systems

pH Scale:

  • Acidic: pH < 7 (High H⁺ concentration).

  • Neutral: pH = 7.

  • Basic (Alkaline): pH > 7 (Low H⁺ concentration).

  • Normal Blood pH: 7.35 - 7.45.

Carbonic Acid-Bicarbonate Buffer System:

  • Acidosis (Low pH): Bicarbonate binds with H⁺ to form carbonic acid, reducing H⁺ concentration.

  • Alkalosis (High pH): Carbonic acid dissociates into bicarbonate and H⁺, increasing H⁺ concentration.

Organic Molecules: The 4 Major Macromolecules

Carbohydrates

  • Function: Quick energy & some cell structure.

  • Monomers: Monosaccharides (Simple Sugars)

    • Pentose Sugars (C₅H₁₀O₄): Ribose (RNA), Deoxyribose (DNA).

    • Hexose Sugars (C₆H₁₂O₆): Glucose, Fructose, Galactose.

  • Disaccharides: Two monosaccharides linked (e.g., sucrose, lactose, maltose).

  • Polysaccharides: Long chains of glucose (e.g., glycogen, starch).

Lipids

  1. Triglycerides: Energy storage (fats/oils).

  2. Phospholipids: Major component of cell membranes.

  3. Steroids: Hormones (e.g., cholesterol, testosterone, estrogen).

  4. Eicosanoids: Cell signaling (e.g., prostaglandins, leukotrienes).

Proteins

  • Functions: Enzymes, structure, movement, transport.

  • Monomers: Amino Acids (Acid group, Amine group, R group).

  • Protein Folding Levels:

    • Primary: Sequence of amino acids.

    • Secondary: Helices & pleated sheets.

    • Tertiary: 3D shape.

    • Quaternary: Multiple polypeptide chains.

Nucleic Acids

  • Monomer: Nucleotides (Pentose sugar, phosphate group, nitrogen base).

  • DNA: Double-stranded, bases A-T, G-C.

  • RNA: Single-stranded, bases A-U, G-C.

Adenosine Triphosphate (ATP)

  • Function: Energy currency of the cell.

  • Structure: Adenine, ribose, 3 phosphate groups (high-energy bonds).

  • ATP Hydrolysis: Releases energy for cellular work.