General Biology
"Life Science! Mula cells hanggang organisms. Biology ang foundation ng lahat ng health sciences - Medicine, Nursing, at iba pa. Master this para strong ang base mo sa STEM!"
1 The Central Dogma of Molecular Biology
DNA → RNA → Protein
The flow of genetic information in all living organisms
1. DNA Replication
DNA copies itself before cell division
- • Helicase: Unwinds DNA
- • DNA Polymerase: Adds nucleotides
- • Leading strand: Continuous
- • Lagging strand: Okazaki fragments
2. Transcription
DNA → mRNA (in nucleus)
- • Initiation: RNA polymerase binds
- • Elongation: mRNA synthesized
- • Termination: Stop signal
- • mRNA Processing: Splicing, capping
3. Translation
mRNA → Protein (in ribosomes)
- • Codon: 3-base sequence
- • tRNA: Brings amino acids
- • Anticodon: Matches codon
- • AUG: Start codon (Methionine)
2 Cell Division - Mitosis vs Meiosis
| Aspect | Mitosis | Meiosis |
|---|---|---|
| Purpose | Growth, repair, asexual reproduction | Sexual reproduction (gamete formation) |
| Cell Type | Somatic (body) cells | Germ cells (sex cells) |
| Daughter Cells | 2 identical (diploid, 2n) | 4 unique (haploid, n) |
| Divisions | 1 division | 2 divisions (Meiosis I & II) |
| Crossing Over | None | Yes (genetic variation) |
Mitosis Phases (PMAT):
Prophase → Metaphase → Anaphase → Telophase
3 Cell Structure and Organelles
Eukaryotic Cell Organelles
- Nucleus: Control center, contains DNA
- Ribosome: Protein synthesis (free or on RER)
- Rough ER: Protein modification (has ribosomes)
- Smooth ER: Lipid synthesis, detoxification
- Golgi Apparatus: Packaging and shipping
- Mitochondria: Powerhouse (ATP production)
- Lysosome: Digestion (suicide bags)
- Vacuole: Storage (large in plant cells)
Plant vs Animal Cells
| Structure | Plant | Animal |
|---|---|---|
| Cell Wall | Present | Absent |
| Chloroplast | Present | Absent |
| Centrioles | Absent | Present |
| Vacuole | Large central | Small/multiple |
4 Genetics and Heredity
Mendel's Laws
- Law of Dominance: Dominant allele masks recessive
- Law of Segregation: Alleles separate during gamete formation
- Law of Independent Assortment: Genes on different chromosomes sort independently
Key Terms
- Genotype: Genetic makeup (AA, Aa, aa)
- Phenotype: Physical expression
- Homozygous: Same alleles (AA or aa)
- Heterozygous: Different alleles (Aa)
- Dominant: Uppercase (A)
- Recessive: Lowercase (a)
Punnett Square (Aa x Aa)
| A | a | |
| A | AA | Aa |
| a | Aa | aa |
Ratio: 1 AA : 2 Aa : 1 aa (3:1 phenotype)
5 Energy in Living Systems
Photosynthesis (Plants)
6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂
- Location: Chloroplast
- Light Reaction: Thylakoid (makes ATP)
- Calvin Cycle: Stroma (makes glucose)
- Pigment: Chlorophyll (absorbs light)
Cellular Respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
- Location: Mitochondria
- Glycolysis: Cytoplasm (2 ATP)
- Krebs Cycle: Matrix (2 ATP)
- ETC: Inner membrane (34 ATP)
Key Insight:
Photosynthesis and Cellular Respiration are OPPOSITE reactions! Plants do both (day: photosynthesis dominant, night: respiration only).
6 Evolution and Biodiversity
Darwin's Theory of Natural Selection
- Variation: Individuals differ in traits
- Inheritance: Traits are passed to offspring
- Selection: Favorable traits increase survival
- Adaptation: Population changes over time
Evidence of Evolution
- • Fossil records
- • Comparative anatomy
- • Molecular biology
- • Biogeography
- • Embryology
Homologous vs Analogous
- Homologous: Same structure, different function (human arm vs whale flipper)
- Analogous: Different structure, same function (bird wing vs insect wing)
Classification (Taxonomy)
King Philip Came Over For Good Soup
- Kingdom → Phylum → Class → Order → Family → Genus → Species
7 Ecology and Ecosystems
Levels of Organization
Organism → Population → Community → Ecosystem → Biome → Biosphere
Ecological Relationships
- Mutualism: Both benefit (+/+)
- Commensalism: One benefits, other unaffected (+/0)
- Parasitism: One benefits, other harmed (+/-)
- Predation: Predator-prey (+/-)
- Competition: Both harmed (-/-)
Food Chain and Energy Flow
Sun → Producers (10%) → Primary Consumers (1%) → Secondary → Tertiary
10% Rule: Only 10% of energy transfers to the next trophic level
Practice Questions
1. What is the correct sequence of the Central Dogma?
Show Answer
DNA → RNA → Protein. This describes the flow of genetic information from DNA through transcription to RNA, then translation to Protein.
2. How many daughter cells are produced in meiosis and what is their ploidy?
Show Answer
4 haploid (n) daughter cells. Meiosis involves two divisions and results in genetically unique cells for sexual reproduction.
3. In a cross between Aa x Aa, what is the phenotypic ratio?
Show Answer
3:1 (3 dominant phenotype : 1 recessive phenotype). Genotypic ratio is 1 AA : 2 Aa : 1 aa.
4. Where does the Krebs Cycle occur?
Show Answer
Mitochondrial matrix. Glycolysis occurs in the cytoplasm, and the Electron Transport Chain occurs in the inner mitochondrial membrane.
Exam Tips for General Biology
- ✓ Memorize PMAT for mitosis phases: Prophase, Metaphase, Anaphase, Telophase
- ✓ Central Dogma: DNA → RNA → Protein (remember the arrow directions!)
- ✓ Photosynthesis vs Respiration: They are opposite reactions - learn both equations
- ✓ Taxonomy mnemonic: King Philip Came Over For Good Soup
- ✓ Punnett Squares: Practice solving monohybrid and dihybrid crosses
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