HESI A2 Biology Review Notes

Introduction

• Overview of key concepts for HESI A2 Biology.
• Importance of understanding scientific methods, macromolecules, genetics, cell structures, and biological processes.

Scientific Method

1. Observation
   • Initial stage; involves noticing and describing events.
2. Hypothesis
   • A testable prediction based on observations.
3. Experiments
   • Conducting tests to gather evidence; involves variables and control groups.
4. Conclusion
   • Final stage; interpretation of data to support or refute the hypothesis.

Importance of Water

• Essential for life; human body ~60% water, Earth's surface ~71% water.

Levels of Biological Organization

1. Atoms and Molecules
   • Atoms form molecules.
2. Macromolecules
   • Large molecules like nucleic acids and proteins.
3. Organelles
   • Structures within cells, e.g., mitochondria, nucleus.
4. Cells
   • Basic unit of life, e.g., red blood cells.
5. Tissues
   • Groups of cells performing similar functions.
6. Organs
   • Structures composed of tissues, e.g., heart, lungs.
7. Organ Systems
   • Groups of organs working together, e.g., respiratory system.
8. Organism
   • Complete living entity.
9. Population
   • Group of organisms of the same species.

Macromolecules

1. Carbohydrates
   • Saccharides, cellulose, starch, glycogen.
2. Nucleic Acids
   • DNA and RNA, carriers of genetic information.
3. Proteins
   • Composed of 20 amino acids.
4. Lipids
   • Includes triglycerides, phospholipids, waxes, steroids.

DNA and RNA

• DNA: Double helix; nucleotides adenine (A), thymine (T), cytosine (C), guanine (G).
• RNA: Single-stranded; nucleotides adenine (A), uracil (U), cytosine (C), guanine (G).
• Genetic sequence knowledge important for HESI.

Genetics and Punnett Squares

• Genotype: Genetic makeup.
• Phenotype: Physical traits.
• Alleles: Versions of a gene; dominant (capitalized) and recessive (lowercase).
• Heterozygous: Different alleles.
• Homozygous: Same alleles.
• Punnett Squares: Tool to predict genetic patterns and genotype ratios.

Organelles

1. Nucleolus: Ribosome formation site.
2. Nucleus: Monitors cell activity, DNA/RNA synthesis.
3. Centrosomes: Cell division involvement.
4. Mitochondria: "Powerhouse," energy production.
5. Ribosomes: Protein synthesis.
6. Endoplasmic Reticulum
   • Rough ER: Protein synthesis, membrane production.
   • Smooth ER: Lipid/steroid storage, detoxification.
7. Lysosomes: Waste disposal.
8. Vacuoles: Storage.
9. Golgi Apparatus: Packing, processing, and shipping.

Plant Cell Structures

• Cell Wall: Not present in animal cells.
• Chloroplast: Contains chlorophyll for photosynthesis.

Eukaryotic vs. Prokaryotic Cells

• Eukaryotic Cells: Larger, more complex, nucleus present.
• Prokaryotic Cells: Smaller, simpler, no true nucleus.

Cell Reproduction

• Mitosis: Growth/repair, results in two diploid cells.
• Meiosis: Sexual reproduction, results in four haploid cells.

Stages of Mitosis and Meiosis

• Prophase: Chromosome condensation.
• Metaphase: Chromosome alignment.
• Anaphase: Separation of chromatids/ chromosomes.
• Telophase: Formation of new nuclei.
• Cytokinesis: Cell division.

Taxonomy and Classification

• Mnemonic: Dear King Philip Came Over From Germany Saturday.
  • Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Metamorphosis Stages

1. Egg: Hatch into larva.
2. Larva: Caterpillar phase; energy storage.
3. Pupa: Transformation stage (cocoon).
4. Adult: Butterfly, focuses on reproduction.