BIOLOGY REVIEWER
I. The Study of Life
1. Definition of Biology
- Biology is the study of living organisms and their interactions with the
environment.
2. Characteristics of Living Things
- Composed of cells
- Use energy (metabolism)
- Respond to stimuli
- Grow and develop
- Reproduce
- Maintain homeostasis
- Adapt through evolution
3. Levels of Biological Organization
- Cell → Tissue → Organ → Organ System → Organism → Population →
Community → Ecosystem → Biosphere
II. Cell Biology
1. Parts of the Cell (Functions)
- Nucleus: Control center; contains DNA.
- Mitochondria Powerhouse of the cell; produces ATP.
- Chloroplasts (plants): Photosynthesis occurs here.
- Ribosomes: Protein synthesis.
- Endoplasmic Reticulum: Transport of materials (rough: with ribosomes;
smooth: lipid synthesis).
- Cell Membrane: Regulates entry/exit of substances.
2. Types of Cells
- Prokaryotic: No nucleus, simple structure (e.g., bacteria).
- Eukaryotic: With nucleus, complex structure (e.g., plants and animals).
3. Cell Cycle
- Stages: Interphase (G1, S, G2), Mitosis, Cytokinesis.
- Mitosis Phases: Prophase → Metaphase → Anaphase → Telophase.
III. Genetics
1. Mendelian Genetics
- Law of Segregation: Alleles separate during gamete formation.
- Law of Independent Assortment: Genes for different traits are inherited
independently.
- Punnett Square: Tool to predict offspring genotypes.
2. DNA Structure and Function
- Components: Phosphate, sugar (deoxyribose), nitrogenous bases
(Adenine-Thymine, Cytosine-Guanine).
- Replication: DNA makes an identical copy during the S phase.
3. Central Dogma of Molecular Biology
- DNA → RNA → Proteinl
- Transcription: DNA → mRNA.
- Translation: mRNA → Protein.
IV. Human Anatomy and Physiology
1. Body Systems
- Circulatory System: Transports blood, nutrients, oxygen.
- Heart, blood vessels (arteries, veins, capillaries).
- Respiratory System: Gas exchange (oxygen in, carbon dioxide out).
- Lungs, trachea, diaphragm.
-Digestive System: Breaks down food into nutrients.
- Mouth, esophagus, stomach, intestines.
-Nervous System: Controls and coordinates body activities.
- Brain, spinal cord, nerves.
2. Key Processes
- Homeostasis: Maintaining stable internal conditions.
- Circulation: Blood flow through the heart and body.
V. Ecology
1. Levels of Ecology
- Population: Group of individuals of the same species.
- Community: Different populations interacting.
- Ecosystem: Community + abiotic factors.
- Biosphere: All ecosystems on Earth.
2. Food Chain and Web
- Producers: Plants (make their own food via photosynthesis).
- Consumers: Herbivores, carnivores, omnivores.
- Decomposers: Break down organic material (e.g., fungi, bacteria).
3. Energy Flow
- Energy decreases as it moves up the trophic levels (10% Rule).
VI. Evolution and Classification
1. Theory of Evolution
- Natural Selection: Survival of the fittest; Charles Darwin.
- Evidence: Fossils, comparative anatomy, molecular biology.
2. Taxonomy
- Hierarchy: Kingdom → Phylum → Class → Order → Family → Genus →
Species.
- Binomial Nomenclature: Two-part naming system (Genus + species).
- Example: Homo sapiens (humans).
VIII. Quick Reference Cheat Sheet
- Mitosis Stages: PMAT (Prophase, Metaphase, Anaphase, Telophase).
- DNA Bases: A-T, C-G.
- 7 Characteristics of Life: Movement, Respiration, Sensitivity, Growth,
Reproduction, Excretion, Nutrition (MRS GREN).
- Photosynthesis Equation:
6CO_2 + 6H_2O → C_6H_{12}O_6 + 6O_2
Advanced and Expanded Biology Reviewer/Notes
I. Molecular Biology and Biochemistry
1. Structure of Biomolecules
Carbohydrates:
- Monosaccharides (e.g., glucose) are the basic units of carbohydrates.
- Disaccharides (e.g., sucrose) are formed by the bonding of two
monosaccharides.
- Polysaccharides (e.g., starch, cellulose) are large polymers formed by
repeating units of monosaccharides.
Diagram of a Glucose Molecule (C₆H₁₂O₆):
- Carbon backbone with hydroxyl (OH) groups attached.
- Glucose is a hexose sugar (6 carbon atoms).
Proteins:
- Proteins are composed of amino acids linked by peptide bonds.
- Diagram of a Protein Structure:
- Primary structure: Sequence of amino acids.
- Secondary structure: α-helix or β-pleated sheet.
- Tertiary structure: 3D folding pattern.
- Quaternary structure: Multiple polypeptide chains interacting.
Lipids:
- Diagram of a Phospholipid:
- Hydrophilic head (glycerol + phosphate group) and hydrophobic tail (fatty
acid chains).
- Key components of cell membranes
2. Enzymes and Metabolism
Enzyme-Substrate Interaction:
- Enzymes lower the activation energy of reactions, facilitating the
conversion of substrates to products.
Diagram of Enzyme Action:
- Shows the enzyme active site, substrate binding, and product formation.
- Lock and Key Model: The enzyme’s active site is complementary to the
substrate’s shape.
3. Cellular Respiration
Cellular respiration involves the breakdown of glucose to produce ATP, the
cell’s energy currency.
Aerobic Respiration:
1.Glycolysis: Breakdown of glucose to pyruvate (occurs in the cytoplasm).
2. Krebs Cycle: Occurs in mitochondria, generating NADH and FADH₂.
3. Electron Transport Chain (ETC) Located in the inner mitochondrial
membrane, produces ATP.
Diagram of Aerobic Respiration:
- Glucose → Glycolysis → Pyruvate → Krebs Cycle → Electron Transport Chain
→ ATP.
- ATP is produced during the final stages in the mitochondria.
II. Advanced Genetics
1. DNA Replication
Process of DNA Replication:
- DNA replication is semi-conservative, meaning each new DNA molecule
consists of one original and one newly synthesized strand.
Diagram of DNA Replication:
- Helicase unwinds the DNA double helix.
- DNA polymerase adds nucleotides in the 5’ → 3’ direction.
- Leading strand is synthesized continuously, while the lagging strand is
synthesized in Okazaki fragments.
2. Transcription and Translation
Transcription (DNA → RNA):
- RNA polymerase reads the DNA and synthesizes mRNA.
Diagram of Transcription:
- RNA polymerase attaches to the promoter region of DNA.
- The mRNA strand is complementary to the DNA template strand.
Translation (RNA → Protein):
- mRNA is translated into a sequence of amino acids at the ribosome,
creating a polypeptide chain.
Diagram of Translation:
- mRNA codons match tRNA anticodons, bringing in amino acids.
- Ribosome links amino acids into a protein chain.
3. Genetic Mutations
Types of Mutations:
- Point mutations: Substitution, insertion, or deletion of a single nucleotide.
- Frame shift mutations: Insertion or deletion that shifts the reading frame.
Diagram of Point Mutation:
- Normal DNA: ATG CCG TGA → Mutated DNA: ATG CCA TGA (substitution
of a single nucleotide).
III. Advanced Physiology
1. Neurobiology
Action Potential:
- Action potential is the electrical impulse that travels along neurons,
essential for nerve signal transmission.
Diagram of Action Potential:
- Resting potential: Na⁺ outside, K⁺ inside.
- Depolarization: Na⁺ channels open, Na⁺ enters.
- Repolarization: K⁺ channels open, K⁺ exits.
- Hyperpolarization: Overshoot of K⁺ exiting.
- Return to resting potential.
2. Endocrine System
Feedback Mechanisms:
- Negative feedback: Homeostasis regulation (e.g., insulin secretion in
response to high blood glucose levels).
- Positive feedback: Amplification of a response (e.g., oxytocin during
childbirth).
Diagram of Negative Feedback (Insulin Regulation):
- High blood glucose → Pancreas releases insulin → Insulin allows cells to
absorb glucose → Blood glucose returns to normal.
IV. Advanced Ecology
1. Biogeochemical Cycles
Carbon Cycle:
- The movement of carbon through the atmosphere, biosphere, and
geosphere.
- Carbon is absorbed by plants during photosynthesis and released by
organisms during respiration.
Diagram of the Carbon Cycle:
- Photosynthesis → Plants → Herbivores → Decomposers → Fossil fuels
(combustion).
2. Population Dynamics
Carrying Capacity (K):
- The maximum population size an environment can support.
- Populations grow rapidly in the absence of limiting factors but stabilize at K
due to environmental resistance.
Diagram of Logistic Growth:
- Population grows exponentially initially, but growth slows and stabilizes
as resources become limited, forming an S-shaped curve.
V. Molecular Biology and Biochemistry
1. Structure of Biomolecules
- Carbohydrates:
- Monosaccharides (e.g., glucose, fructose).
- Disaccharides (e.g., sucrose, lactose).
- Polysaccharides (e.g., starch, glycogen, cellulose).
- Lipids
- Triglycerides: Glycerol + 3 fatty acids.
- Phospholipids: Amphipathic molecules (key in cell membranes).
- Steroids: Cholesterol and hormones (e.g., testosterone).
- Proteins:
- Made of amino acids (linked by peptide bonds).
- Levels of protein structure: Primary, secondary (α-helix, β-pleated
sheets), tertiary, quaternary.
- Nucleic Acids:
- DNA: Double helix; bases (A-T, G-C).
- RNA: Single-stranded; bases (A-U, G-C).
2. Enzymes
- Biological catalysts; lower activation energy.
- Key Properties:
- Highly specific.
- Affected by pH, temperature, and substrate concentration.
- Enzyme activity graph: Optimal conditions show peak activity.
3. Cellular Respiration
- Aerobic Respiration:
C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + 36-38 \, ATP
- Stages: Glycolysis → Krebs Cycle → Electron Transport Chain (ETC).
- Anaerobic Respiration: Occurs without oxygen (e.g., lactic acid
fermentation).
4. Photosynthesis
- Light-dependent reactions: Occur in thylakoid membranes; produce ATP
and NADPH.
- Light-independent reactions (Calvin Cycle): Occur in stroma; synthesize
glucose.
VI. Advanced Genetics
1. DNA Replication
- Semi-conservative process: One parental strand and one new strand.
- Enzymes involved:
- Helicase: Unwinds DNA.
- DNA polymerase: Adds nucleotides.
- Ligase: Seals Okazaki fragments on lagging strand.
2. Gene Expression
- Transcription: DNA → mRNA (occurs in nucleus).
- Translation: mRNA → Protein (occurs in ribosomes).
- Codons: Triplets of bases in mRNA.
- Start codon: AUG (Methionine).
- Stop codons: UAA, UAG, UGA.
3. Genetic Mutations
- Types:
- Point mutations: Substitution, insertion, deletion.
- Chromosomal mutations: Inversion, duplication, translocation.
- Effects: Silent, missense, nonsense mutations.
4. Biotechnology
- Polymerase Chain Reaction (PCR): Amplifies DNA.
- Gel Electrophoresis: Separates DNA fragments by size.
- CRISPR-Cas9: Genome editing tool.
VII. Advanced Physiology
1. Neurobiology
- Neuron Structure: Cell body, dendrites, axon, synapse.
- Action Potential: Depolarization (Na+ influx), repolarization (K+ efflux),
hyperpolarization.
- Neurotransmitters: Acetylcholine, dopamine, serotonin.
2. Endocrine System
- Hormones: Chemical messengers transported in blood.
- Examples: Insulin (lowers blood glucose), Glucagon (raises blood
glucose).
- Feedback Mechanisms:
- Negative feedback (e.g., blood glucose regulation).
- Positive feedback (e.g., oxytocin during childbirth).
3. Immunology
- Innate Immunity: Non-specific defenses (e.g., skin, phagocytes).
- Adaptive Immunity: Specific defenses (e.g., B-cells, T-cells).
- B-cells: Produce antibodies.
- T-cells: Cytotoxic T-cells destroy infected cells.
VIII. Advanced Ecology
1. Biogeochemical Cycles
- Carbon Cycle: Includes photosynthesis, respiration, combustion.
- Nitrogen Cycle: Nitrogen fixation, nitrification, denitrification.
- Water Cycle: Evaporation, condensation, precipitation.
2. Population Dynamics
- Carrying Capacity (K): Maximum population an environment can sustain.
- Logistic Growth: S-shaped curve (population stabilizes at K).
- Exponential Growth: J-shaped curve (unchecked growth).
3. Ecosystem Stability
- Keystone species: Disproportionate effect on ecosystem stability.
- Biodiversity: Increases resilience to disturbances.
