Chemistry of Life

Covalent bond

Atoms share electrons.
Strongest bond
Nonmetal

Nonpolar Covalent bond

Electrons are shared equally between the atoms

Polar Covalent bond

Electrons are shared unequally

Ionic bond

Electrons are transferred between atoms, creating charged ions.
Metal to nonmetal
Salt Compound

Hydrogen bond

Weak bonds between a hydrogen atom and an electronegative atom.

Van der Waals Forces

Weak, short-range forces between all atoms. Between neutral atoms

Anion

Negative ion (gains electrons).

Cation

Positive ion (loses electrons).

Isostope

Different neurons

Buffers

Resist changes in pH by neutralizing excess acids or bases.

Decomposition Reactions

A single compound breaks down into two or more simpler substances.
AB→A+B

Synthesis Reactions

Two or more simple substances combine to form a more complex substance.
A+B→AB

Exchange Reactions

Components of two compounds swap places.
AB+CD→AD+CB

Reversible Reactions

Reactions where products can react to form the original reactants, proceeding in both directions.
A+B↔AB

Endergonic Reaction

Reactions that absorb energy from their surroundings

Exergonic Reactions

Reactions that release energy to their surroundings

Anabolic Reactions

Metabolic pathways that build complex molecules from simpler ones, requiring an input of energy.

Catabolic Reactions

Metabolic pathways that break down complex molecules into simpler ones, releasing energy.

Carboxyl Group

• Formula: −COOH-COOH−COOH

• Structure: Carbonyl group (C=OC=OC=O) + Hydroxyl group (−OH-OH−OH)

• Example: Acetic acid (CH₃COOH)

Lipids

• Definition: Hydrophobic organic compounds (fats, oils, waxes, phospholipids).

• Importance:

  • Energy Storage: Efficient storage of energy.

  • Cell Membrane Structure: Phospholipids and cholesterol maintain membrane fluidity.

  • Insulation & Protection: Fat insulates and protects organs.

  • Hormone Production: Precursor to steroid hormones.

Cholesterol

• Definition: A steroid lipid found in cell membranes.

• Functions:

  • Cell Membrane Fluidity: Maintains membrane stability.

  • Precursor to Hormones: Synthesizes steroid hormones (e.g., cortisol, testosterone).

  • Bile Production: Forms bile acids for digestion.

  • Vitamin D Synthesis: Converted to vitamin D by sunlight

Proteins

• Definition: Large molecules made of amino acid chains.

• Structure: Amino acids with general formula NH2−CHR−COOH\text{NH}_2-\text{CHR}-\text{COOH}NH2​−CHR−COOH.

• Functions:

  • Enzymes: Catalyze reactions.

  • Structural Support: (e.g., collagen)

  • Transport: (e.g., hemoglobin)

  • Regulation: (e.g., hormones like insulin)

Nucleic Acids

• Types: DNA & RNA

• Functions:

  • DNA: Stores genetic information, double helix structure.

  • RNA: Involved in protein synthesis and gene regulation.

    • mRNA: Carries genetic code from DNA.

    • tRNA: Delivers amino acids to ribosomes.

    • rRNA: Part of ribosome structure.