Chemistry of Life – Topic 2 Notes

Matter is anything that has mass and takes up space.
Elements are the basic building blocks of matter that cannot be broken down by chemical means.
Atoms are the smallest units of an element that retain the element's physical and chemical properties. These atoms bond together to form molecules.

Ionic bonds
- Atoms in this bond donate or take on electrons.
- Result in a stable outer shell.
- Occur between particles that are charged (ions).
- Example: Sodium chloride (NaCl) formed by electrical attraction between Na⁺ and Cl⁻.
- Sodium atom: 1 electron in outer shell; loses 1 electron to become Na⁺.
- Chlorine atom: 7 electrons in outer shell; gains 1 electron to become Cl⁻.
Covalent bonds
- Atoms share electrons.
- Result in a stable outer shell.
- Example drawings show bonding leading to compounds like NaCl (ionic) and molecules like H₂O (covalent).
- Water formation: when an oxygen and two hydrogen atoms covalently bond, water results: ext{H}_2 ext{O}
- Oxygen molecule (O₂) is formed by covalent bonding of two oxygen atoms.
Hydrogen bonds
- Occur between a hydrogen in a covalent bond and a negatively charged atom.
- These are relatively weak bonds compared to covalent or ionic bonds.
- Hydrogen bonding plays a key role in water molecule interactions (e.g., between water molecules).

Water is liquid at room temperature.
Liquid water does not change temperature quickly (high heat capacity).
Water has a high heat of evaporation (high heat of vaporization).
Frozen water is less dense than liquid water.
Molecules of water cling together (cohesion) and water is a solvent for polar molecules (solvent properties).
These properties make water essential for life processes.

Acids: substances that dissociate and release hydrogen ions (H⁺).
Bases: substances that take up hydrogen ions (H⁺) or release hydroxide ions (OH⁻).
pH scale measures hydrogen ion concentration.
- Working range: 0 \leq \text{pH} \leq 14 with 7 being neutral.
- A pH below 7 is acidic; a pH above 7 is basic.
- The concentration of hydrogen ions between each whole pH number changes by a factor of 10 (each unit change corresponds to a tenfold change in [H⁺]).
Formula: \text{pH} = -\log_{10}([H^+])
Examples of substances along the pH scale (as shown on the slide): Battery acid, stomach acid, lemon juice, tomato juice, milk, vinegar, coffee, pure water, blood, baking soda, soap, soda, ammonia, and others.

The four major organic macromolecules (made mainly of Carbon and Hydrogen) essential for life:
1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic acids
Carbohydrates (focus in these notes for this section):
- Subunits: monosaccharides.
- General composition: \mathrm{C!:\;H:\;O} in a 1:2:1 ratio, often summarized as the empirical formula \mathrm{CH_2O}.
- Function: energy storage (both short-term and long-term).
- Forms: simple and complex carbohydrates.
- Simple carbohydrates
- Monosaccharide: 1 carbon ring (as found in glucose).
- Disaccharide: 2 carbon rings (as in maltose).
- Examples and representations from the slide:
  - Glucose: \mathrm{C6H{12}O_6}
  - Maltose: \mathrm{C{12}H{22}O_{11}}
- Complex carbohydrates
- Polysaccharides: many carbon rings linked together.
- Glycogen: storage form in animals.
- Starch: storage form in plants.
- Visual hints from the slide include representations like CH₂OH groups attached to carbon rings, illustrating common monosaccharide structure.
Lipids, Proteins, and Nucleic Acids
- These macromolecules are listed as essential, but detailed subunits and functions are not provided in these pages beyond their identification as major macromolecules.

The material connects basic chemistry (atoms, bonds, water) to biology (macromolecules that sustain life).
Understanding bonds explains molecule formation (ionic vs covalent) and molecular interactions (hydrogen bonding in water).
Water’s properties underpin biochemical reactions and cellular environments.
Acids, bases, and pH regulate biological processes (e.g., blood pH homeostasis is crucial for enzyme activity and metabolism).
Carbohydrates provide immediate and stored energy, with structural roles in some organisms (through polysaccharides).
The four macromolecules collectively underpin the structure and function of living organisms: energy storage (carbohydrates and lipids), catalysis and structure (proteins), and information storage and transfer (nucleic acids).

pH relation to hydrogen ions: \text{pH} = -\log_{10}([H^+]), with each unit change in pH corresponding to a factor of 10 change in [H^+].
Carbohydrate general empirical formula: \mathrm{CH2O} (repeating unit); actual glucose formula: \mathrm{C6H{12}O6}; maltose formula: \mathrm{C{12}H{22}O_{11}}.
Water formula: \mathrm{H_2O}
Ionic bond example: NaCl (Na⁺ with Cl⁻ formation via electron transfer).
Covalent bond example: H–O–H in water, O=O in O₂ (sharing electrons).
Hydrogen bond: interaction between a hydrogen attached to a highly electronegative atom (like O) and another electronegative atom (like O) in a separate molecule or region.