Notes on Biology OCR A-Level Lecture

Introduction

• Dr. Albert and Dr. Edwards team teaching OCR A-Level Biology
• Suggestions: watch at 2x speed, access chapters via timestamps/description
• Website resources: multiple-choice questions, predictive paper video walkthroughs
• Key cell biology concepts to understand: structures/functions of eukaryotic cells (plants/animals), prokaryotic cells, microscopy basics, measuring cells, cell replication, biochemistry basics

Eukaryotic Cells

• Common structures in both plant and animal cells: nucleus, cell surface membrane, mitochondria, ribosomes, Golgi apparatus
  • Nucleus: Contains chromosomes (DNA), nuclear envelope, nucleolus (ribosome production)
  • Cell Surface Membrane: Controls movement in/out of cell, composed of lipids/proteins
  • Mitochondria: Double membrane, inner membrane folded, site of respiration and ATP production
  • Ribosomes: Found on rough ER/in cytoplasm, site of protein synthesis
  • Golgi Apparatus: Produces new lipids/proteins, forms Golgi vesicles for storage/transport
• Unique to plant cells: chloroplasts, cell wall, central vacuole
  • Chloroplasts: Site of photosynthesis, double membrane, thylakoids
  • Cell Wall: Maintains cell structure
  • Central Vacuole: Contains sap, maintains cell shape/pressure

Prokaryotic Cells

• Features: Cytoplasm, ribosomes, cell surface membrane, cell wall
• Unique features: Flagella, DNA in cytoplasm (single coiled strand), plasmid DNA, capsules
• Most structures in prokaryotes similar to eukaryotes, aside from organization and membrane-bound organelles

Measurement & Microscopy

• Units of measurement: Millimeters (mm), micrometers (µm), nanometers (nm)
• Relationships: 1 mm = 1000 µm, 1 µm = 1000 nm
• Types of microscopes: Optical (light) microscopes, electron microscopes (TEM/SEM)
  • Optical: Light-based, living specimens, color images, max magnification ~1500x
  • Electron: Electron-based, dead specimens, black-and-white images, high magnification (up to 1.5 million x)
• Microscope calculations: Magnification = image size / actual size
• Biological drawings: Sharp pencil, include scale, clear lines, no shading, title, accuracy

Biochemistry Basics

• Bonding: Covalent, ionic, hydrogen bonding
• Water: Polarity, hydrogen bonding, properties (cohesion, solvent abilities), metabolite
• Biological molecules: Role and structure of carbohydrates, lipids, proteins, nucleic acids
• Enzymes: Biological catalysts, lower activation energy, depend on substrate specificity
  • Lock and Key vs. Induced Fit Models: Specific substrate fits enzyme active site

Cell Division (mitosis and meiosis)

• Mitosis: Produces 2 identical daughter cells, stages include prophase, metaphase, anaphase, telophase, and cytokinesis
• Meiosis: Produces 4 non-identical gametes, involves two rounds of division (meiosis I and II), key for genetic diversity (crossing over, independent assortment)
• Stem cells and differentiation: Importance in development, potential uses in medicine, ethical considerations

Genetics

• DNA structure and replication: Semi-conservative replication, role of DNA polymerase and helicase
• Transcription and translation: mRNA synthesis in nucleus (transcription), protein synthesis in cytoplasm (translation)
• Gene expression and regulation: Transcription factors (activators/repressors), environmental influences, epigenetics

Metabolism

• Photosynthesis: Light-dependent and light-independent reactions, role of chlorophyll, electron transport chain
• Respiration: Glycolysis, link reaction, Krebs cycle, oxidative phosphorylation, ATP production
• Practical applications and experiments: Chromatography for separating mixtures, use of respirometers for measuring respiration rates

Ecology and Ecosystems

• Energy transfer: Food chains/webs, trophic levels, biomass pyramids, limitations of energy transfer
• Nutrient cycles: Role of decomposers, nitrogen cycle, carbon cycle
• Succession: Primary and secondary succession, climax communities, human impacts on succession
• Biodiversity and conservation: Importance of maintaining biodiversity, conservation strategies, human impact on ecosystems

Biotechnology and Genetic Engineering

• Applications: GMOs, medical uses (gene therapy, production of pharmaceuticals), ethical considerations
• Techniques: PCR, electrophoresis, cloning (in vivo and in vitro), gene editing technologies
• Genetic fingerprinting: Use in forensics, medical diagnosis, population genetics

Summary

• Important themes: Cell structure/function, biochemistry, genetic principles, cell division, metabolism, ecology, conservation, biotechnology
• Practical skills and applications: Microscopy, enzyme investigations, genetic experiments, ecological sampling, genetic modifications