1. Cell Organelles Quick Reference
| Organelle | Plant / Animal / Both | Function |
|---|---|---|
| Nucleus | Both | Contains DNA; controls cell activities |
| Cell Membrane | Both | Selectively permeable barrier; controls entry/exit |
| Cytoplasm | Both | Gel-like fluid where chemical reactions occur |
| Mitochondria | Both | Produces ATP via cellular respiration (“powerhouse”) |
| Ribosomes | Both | Builds proteins from mRNA instructions |
| Endoplasmic Reticulum (Rough) | Both | Makes proteins (has ribosomes attached) |
| Endoplasmic Reticulum (Smooth) | Both | Makes lipids; detoxifies chemicals |
| Golgi Apparatus | Both | Packages, modifies, and ships proteins |
| Lysosomes | Animal (mainly) | Digests waste and foreign material |
| Cell Wall | Plant only | Rigid outer layer (cellulose); structural support |
| Chloroplasts | Plant only | Photosynthesis (converts light to glucose) |
| Central Vacuole | Plant (large) | Stores water; maintains turgor pressure |
| Centrioles | Animal only | Help organise spindle fibres during cell division |
2. Macromolecules Table
| Macromolecule | Monomer | Examples | Function |
|---|---|---|---|
| Carbohydrates | Monosaccharide (glucose) | Glucose, starch, cellulose, glycogen | Quick energy; structural support (cellulose) |
| Lipids | Glycerol + fatty acids | Fats, oils, phospholipids, waxes | Long-term energy; cell membrane; insulation |
| Proteins | Amino acid (20 types) | Enzymes, haemoglobin, antibodies, collagen | Enzymes, structure, transport, defence |
| Nucleic Acids | Nucleotide | DNA, RNA, ATP | Genetic information storage & transfer |
3. Photosynthesis vs Cellular Respiration
| Photosynthesis | Cellular Respiration | |
|---|---|---|
| Location | Chloroplast | Mitochondria (+ cytoplasm) |
| Reactants | CO₂ + H₂O + light | C₆H₁₂O₆ + O₂ |
| Products | C₆H₁₂O₆ + O₂ | CO₂ + H₂O + ATP |
| Energy | Stored (light → chemical) | Released (chemical → ATP) |
| Organisms | Plants, algae, some bacteria | ALL living organisms |
Respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (~36-38)
4. Genetics Key Terms
- Gene: Segment of DNA coding for a protein/trait
- Allele: Different version of a gene (e.g., T or t)
- Genotype: Allele combination (TT, Tt, tt)
- Phenotype: Observable trait (tall, short)
- Dominant: Expressed when 1 or 2 copies present (T)
- Recessive: Expressed only when 2 copies present (tt)
- Homozygous: Two identical alleles (TT or tt)
- Heterozygous: Two different alleles (Tt)
- Chromosome: Structure of coiled DNA + proteins
- Diploid (2n): Full set of chromosomes (46 in humans)
- Haploid (n): Half the chromosomes (23 in gametes)
- Gamete: Sex cell (egg or sperm), haploid
- Zygote: Fertilised egg (diploid, 46 chromosomes)
- Mutation: Permanent change in DNA sequence
- Codon: Group of 3 mRNA bases coding for 1 amino acid
- Transcription: DNA → mRNA (in nucleus)
- Translation: mRNA → protein (at ribosome)
- Incomplete dominance: Blend of phenotypes (red+white=pink)
- Codominance: Both alleles fully expressed (red AND white)
- Sex-linked: Gene on the X chromosome
5. Punnett Square Quick Guide
Monohybrid Cross: Tt × Tt
| T | t | |
|---|---|---|
| T | TT | Tt |
| t | Tt | tt |
Genotypic ratio: 1 TT : 2 Tt : 1 tt | Phenotypic ratio: 3 dominant : 1 recessive
Key rule: Heterozygous × Heterozygous always gives 3:1 phenotypic ratio.
Hardy-Weinberg: p + q = 1 | p² + 2pq + q² = 1 (p = dominant allele freq, q = recessive)
6. Evolution Key Terms
- Evolution: Change in allele frequencies in a population over generations
- Natural selection: Individuals with favourable traits survive and reproduce more
- Adaptation: Heritable trait that increases fitness in an environment
- Homologous structures: Same structure, different function (common ancestor)
- Analogous structures: Different structure, same function (convergent evolution)
- Vestigial structures: Reduced/nonfunctional remnants of once-useful structures
- Speciation: Formation of a new species (requires reproductive isolation)
- Convergent evolution: Unrelated species become similar (similar environments)
- Divergent evolution: Related species become different (different environments)
- Artificial selection: Humans choose which organisms reproduce (selective breeding)
7. Ecological Levels (Smallest to Largest)
10% Rule: Only ~10% of energy passes from one trophic level to the next. The rest is lost as heat.
Carrying Capacity (K): Maximum population an environment can sustain long-term.
8. Body Systems Quick Overview
| System | Key Organs | Main Function |
|---|---|---|
| Digestive | Mouth, stomach, small/large intestine, liver, pancreas | Break down food, absorb nutrients |
| Circulatory | Heart, blood vessels (arteries, veins, capillaries) | Transport O₂, nutrients, waste; immune cells |
| Respiratory | Lungs, trachea, bronchi, alveoli, diaphragm | Gas exchange (O₂ in, CO₂ out) |
| Nervous | Brain, spinal cord, nerves | Process info, coordinate responses, senses |
| Endocrine | Pituitary, thyroid, pancreas, adrenal glands | Hormones regulate growth, metabolism, reproduction |
| Immune | White blood cells, lymph nodes, thymus, spleen | Defend against pathogens |
| Musculoskeletal | Bones, muscles, joints, tendons, ligaments | Support, protection, movement |
| Excretory | Kidneys, bladder, ureters, skin | Remove waste, regulate water/salt balance |
🐱 Cat Biology Fun Fact!
A cat has 230 bones — more than humans, who have 206! Cat cells contain the exact same organelles as human cells: nucleus, mitochondria, ribosomes, ER, Golgi — the works. Every single one of those 230 bones started as a single fertilised egg cell that divided over and over through mitosis. Cats also have a tapetum lucidum — a reflective layer behind their retinas that bounces light back through the photoreceptors, giving them incredible night vision. This is an evolutionary adaptation for hunting at dawn and dusk!
🎵 Len Kagamine Biology Connection!
If Len Kagamine were a real person, his voice would be produced by vibrations of his vocal cords (in the larynx), powered by air from his lungs (respiratory system), controlled by his brain (nervous system), and fuelled by ATP from cellular respiration (biochemistry). To sing those high notes, he would need approximately 6 litres of lung capacity and incredibly fast nerve impulses to his laryngeal muscles. Every Vocaloid performance is a biology lesson in disguise — respiration, nervous control, and muscle contraction all working together!