2.1.1Additional lessons
Properties of Carbon — IB Biology SL Revision Notes & Topical Questions
5 min read 4 parts Lesson 11 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4Why Carbon Is Special
All four main classes of biological molecule contain carbon, which is why life is described as carbon based.
Four outer electrons
- Four outer electrons A carbon atom has four electrons in its outer shell, so it can form four covalent bonds with other atoms.
Covalent bonding
- Covalent bonding Atoms share a pair of electrons, producing strong and stable bonds that are drawn as single lines between atoms.
Bonding partners
- Bonding partners Carbon bonds with other carbon atoms and with hydrogen, oxygen, nitrogen, sulfur and phosphorus found in living things.
Variety of shapes
- Variety of shapes Carbon atoms can form straight chains, branched chains and rings, giving millions of different compounds.
Examples
- Examples Cellulose is a straight unbranched chain, while glycogen is highly branched, showing how arrangement affects function.
Part 2 of 4Simple Carbon Compounds
Simple Carbon Compounds
Methane
- Methane CH₄ has four single covalent bonds from carbon to hydrogen atoms, arranged around the central carbon atom.
Carbon dioxide
- Carbon dioxide CO₂ has two double bonds, one between carbon and each oxygen atom, with each double bond sharing two pairs of electrons.
Single bonds
- Single bonds Share one pair of electrons and allow rotation, so long chains can bend and fold.
Double bonds
- Double bonds Share two pairs of electrons and hold atoms more rigidly, as in unsaturated fatty acids.
Rings
- Rings Carbon atoms can also join in rings, such as the ring form of glucose, which gives molecules compact and stable shapes.
Part 3 of 4Functional Groups
Functional groups are small groups of atoms that give a molecule its characteristic chemical behaviour.
Hydroxyl, -OH
- Hydroxyl, -OH Polar group found in alcohols and carbohydrates, which makes molecules soluble in water.
Carboxyl, -COOH
- Carboxyl, -COOH Acidic group that can release a hydrogen ion, found in fatty acids and amino acids.
Amino, -NH₂
- Amino, -NH₂ Basic group that can accept a hydrogen ion, found in amino acids.
Phosphate, -PO₄
- Phosphate, -PO₄ Group that carries charge and links to other molecules, found in phospholipids and nucleotides.
| Group | Formula | Found in |
|---|---|---|
| Hydroxyl | -OH | Carbohydrates, alcohols |
| Carboxyl | -COOH | Fatty acids, amino acids |
| Amino | -NH₂ | Amino acids |
| Phosphate | -PO₄ | Phospholipids, nucleotides |
Part 4 of 4Exam Checklist & Tips
2.1.1 – Key Points for the Exam
- Covalent bond A bond formed when two atoms share a pair of electrons.
- Functional group A group of atoms that gives an organic molecule particular chemical properties.
- Organic compound A compound containing carbon, usually bonded to hydrogen.
- Hydroxyl group The -OH group, which is polar and makes molecules water soluble.
- Carboxyl group The -COOH group, which behaves as an acid.
Common Mistakes
- Writing that carbon has four outer shells; it has four electrons in its outer shell.
- Describing a covalent bond as transfer of electrons, which is the description of an ionic bond.
- Confusing the amino group (-NH₂) with the carboxyl group (-COOH).
- Saying that CO₂ has single bonds; each carbon-oxygen bond is a double bond.
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