Biology UIL 2024-2025

1. Relationship Between Structure and Function

This topic focuses on how biological structures are adapted to their functions.

Basic Biochemistry

All living things are made of four macromolecules:

  • Proteins: Made of amino acids; used for structure (collagen), enzymes (catalysts like DNA polymerase), transport (hemoglobin), and signaling (insulin).

  • Carbohydrates: Composed of sugars (monosaccharides like glucose, disaccharides like sucrose, and polysaccharides like starch). They provide energy and structural support.

  • Lipids: Hydrophobic molecules including fats, oils, phospholipids (cell membranes), and steroids (hormones).

  • Nucleic Acids: DNA and RNA, which store and transfer genetic information.

Cell Biology & Membrane Transport

Cells are the fundamental units of life, with prokaryotes (bacteria, archaea) and eukaryotes (plants, animals, fungi, protists) differing in complexity.

  • Organelles & Functions:

    • Nucleus stores genetic material.

    • Mitochondria produce ATP through respiration.

    • Ribosomes make proteins.

    • Endoplasmic Reticulum (ER) processes proteins (rough ER) and lipids (smooth ER).

    • Golgi Apparatus packages proteins for export.

    • Lysosomes break down waste.

    • Chloroplasts (in plants) perform photosynthesis.

Membrane transport is critical for maintaining homeostasis:

  • Passive Transport: No energy required (diffusion, osmosis, facilitated diffusion).

  • Active Transport: Requires ATP (pumps like Na+/K+ pump, endocytosis, exocytosis).

2. Cellular and Acellular Replication

How cells and viruses replicate.

Cell Cycle & Regulation

The cell cycle has distinct phases:

  1. G1 (Growth 1): Cell grows and prepares for DNA replication.

  2. S (Synthesis): DNA replication occurs.

  3. G2 (Growth 2): Cell prepares for division.

  4. M (Mitosis): The cell divides into two identical daughter cells.

  5. Cytokinesis: Cytoplasm splits, completing cell division.

Cell cycle regulation is controlled by cyclins and cyclin-dependent kinases (CDKs) to prevent cancerous growth.

DNA Replication

  • Helicase unwinds DNA.

  • DNA Polymerase builds new strands.

  • Ligase joins fragments on the lagging strand (Okazaki fragments).

Meiosis & Sexual Reproduction

Meiosis produces haploid (n) gametes from diploid (2n) cells in two divisions:

  • Meiosis I: Homologous chromosomes separate.

  • Meiosis II: Sister chromatids separate (like mitosis).

  • Crossing over (prophase I) and independent assortment (metaphase I) create genetic diversity.

Viral Replication

Viruses require a host to reproduce. Two main cycles:

  • Lytic Cycle: Virus injects DNA, hijacks host, makes new viruses, bursts the cell.

  • Lysogenic Cycle: Viral DNA integrates into host genome (provirus) and can stay dormant before activating.

3. Energy Transformations

How organisms obtain and use energy.

Cellular Respiration (Aerobic)

  1. Glycolysis (cytoplasm)

    • Glucose → 2 Pyruvate + 2 ATP + 2 NADH

  2. Krebs Cycle (mitochondria)

    • Pyruvate → CO₂ + NADH + FADH₂ + 2 ATP

  3. Electron Transport Chain (ETC) & Chemiosmosis (inner mitochondrial membrane)

    • NADH & FADH₂ → H₂O + 34 ATP

    • Oxygen is the final electron acceptor.

Anaerobic respiration (fermentation) produces less ATP and leads to lactic acid (animals) or ethanol + CO₂ (yeast).

Photosynthesis

  1. Light-dependent reactions (thylakoid membrane)

    • Water split → O₂, ATP, NADPH

  2. Calvin Cycle (stroma)

    • CO₂ + ATP + NADPH → Glucose

4. Gene Expression

Protein Synthesis

  1. Transcription (Nucleus): DNA → mRNA

    • RNA polymerase makes mRNA from DNA.

  2. Translation (Ribosome): mRNA → Protein

    • tRNA brings amino acids to ribosomes to build proteins.

Mutations & Regulation

  • Point mutations: One base change (silent, missense, nonsense).

  • Frameshift mutations: Insertion/deletion shifts reading frame.

Gene expression is regulated via operons (e.g., lac operon in bacteria).

5. Genetics and Inheritance

  • Mendelian genetics: Dominant/recessive alleles, Punnett squares.

  • Non-Mendelian genetics:

    • Incomplete dominance (red + white = pink)

    • Codominance (blood type AB)

    • Polygenic traits (skin color, height).

DNA technology: PCR, gel electrophoresis, gene editing (CRISPR).

6. Evolution

  • Natural selection (survival of the fittest).

  • Microevolution (mutation, gene flow, genetic drift).

  • Macroevolution (speciation, extinction).

Evidence includes fossils, DNA comparisons, and homologous structures.

7. Origin and Diversity of Life

  • Phylogeny & taxonomy: Domains (Bacteria, Archaea, Eukarya), classification.

  • Animal & plant behavior: Innate vs. learned behaviors, symbiosis.

8. Ecology and Environment

  • Population dynamics: Carrying capacity, logistic vs. exponential growth.

  • Biogeochemical cycles: Carbon, nitrogen, water cycles.

  • Ecosystem stability & food webs.

9. Human Anatomy & Physiology

  • Tissue types: Epithelial, connective, muscle, nervous.

  • Organ systems: Digestive, circulatory, nervous, etc.

  • Homeostasis: Negative feedback loops (e.g., blood sugar regulation).

10. Diseases (Focus: Malaria)

  • Cause: Plasmodium parasite, transmitted by mosquitoes.

  • Symptoms: Fever, chills, anemia, organ failure.

  • Treatment: Antimalarial drugs (quinine, artemisinin).