The Chemical Level of Organization

The Chemical Level of Organization

Why Chemistry Matters

• Body is composed of chemicals.

• Life processes are fundamentally chemical reactions.

• Understanding chemistry is crucial for comprehending physiology.

Matter & Elements

• Matter: Anything that occupies space and has mass.

• Elements: Pure substances (e.g., Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)).

Atoms

• Smallest units of elements.

• Composed of subatomic particles: protons ($positive$), neutrons ($neutral$), electrons ($negative$).

• Ions: Atoms with a net electrical charge due to gain or loss of electrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Atomic number ($Z$): Number of protons.

• Atomic mass ($A$): Protons + Neutrons.

Biological Elements

• 96% of human body: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

• Other significant elements: Phosphorus (P), Sulfur (S), Calcium (Ca), Iron (Fe), Potassium (K), Sodium (Na), Magnesium (Mg).

Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms, forming ions (e.g., $Na^+$ and $Cl^-$ forming $NaCl$).

• Covalent Bonds: Sharing of electrons between atoms.

  • Single, Double, Triple Bonds: Depend on the number of electron pairs shared.

  • Nonpolar Covalent: Equal sharing of electrons (e.g., $O_2$).

  • Polar Covalent: Unequal sharing of electrons, creating partial positive ($\delta+$) and negative ($\delta-$) charges (e.g., $H_2O$).

  • Strongest Bond Type: Polar Covalent Bond.

• Hydrogen Bonds: Weak attraction between molecules, involving a hydrogen atom already bonded to an electronegative atom and another electronegative atom (e.g., important in water and DNA).

  • Bond holding DNA together: Hydrogen Bond.

Chemical Reactions

• Involve reactants converting into products ($Reactants \rightarrow Products$).

• Synthesis Reaction: Two components bond to form a larger molecule (e.g., $A + B \rightarrow AB$).

  • Dehydration Synthesis: Monomers join by removing a water molecule ($H_2O$).

• Decomposition Reaction: Bonds within a larger molecule are broken, yielding smaller products (e.g., $AB \rightarrow A + B$).

  • Hydrolysis: Monomers are released by adding a water molecule ($H_2O$).

• Exchange Reaction: Bonds are formed and broken, rearranging components (e.g., $AB + C \rightarrow AC + B$).

Enzymes

• Biological catalysts that speed up chemical reactions.

• Lower the activation energy required for a reaction.

• Substrates bind to the enzyme's active site to form products.

Energy

• Essential for driving all chemical reactions and life processes within the body.

Acids & Bases

• Acid: A substance that donates hydrogen ions ($H^+$).

• Base: A substance that accepts hydrogen ions ($H^+$) (often releasing hydroxide ions, $OH^-$).

pH Scale

• Measures the acidity or alkalinity of a solution.

• Range: $0$ (most acidic) to $14$ (most basic).

• pH < 7.0: Acidic.

• $pH = 7.0$: Neutral.

• pH > 7.0: Basic (Alkaline).

Buffers

• Solutions that resist changes in pH.

• Critical for maintaining stable pH levels in biological systems (e.g., bicarbonate buffer in blood).

Organic Compounds (Macromolecules)

• The four major classes of biological macromolecules are essential to life.

Carbohydrates

• Sugars and starches.

• Primary function: Energy source.

Lipids

• Fats, oils, phospholipids, and steroids.

• Phospholipids: Have a hydrophilic (polar) head and hydrophobic (nonpolar) tails; form cell membranes.

Proteins

• Composed of amino acids linked by peptide bonds.

• Diverse functions: structural support, enzymes, transport, defense.

• Protein Structure:

  • Primary: Linear sequence of amino acids.

  • Secondary: Local folding (e.g., alpha-helix, beta-pleated sheet).

  • Tertiary: Three-dimensional folding of a single polypeptide chain.

  • Quaternary: Arrangement of multiple polypeptide chains.

Nucleic Acids

• DNA (Deoxyribonucleic Acid): Genetic blueprint; stores hereditary information.

• RNA (Ribonucleic Acid): Involved in protein synthesis.

• Composed of nucleotides: nitrogenous base (Adenine (A), Guanine (G), Cytosine (C), Thymine (T) in DNA, Uracil (U) in RNA), pentose sugar (deoxyribose/ribose), and a phosphate group.

Central Dogma of Molecular Biology

• The flow of genetic information: $DNA \rightarrow RNA \rightarrow Protein$.

• Transcription: DNA is copied into RNA.

• Translation: mRNA (messenger RNA) is used to synthesize protein.

ATP (Adenosine Triphosphate)

• Energy currency of the cell.

• Stores energy in high-energy phosphate bonds.