Lecture Notes: A-Level Biology Paper 1 Overview

Introduction

• Lecture by Miss Estrick
• Comprehensive review for AQA A-Level Biology Paper 1
• Tips: Use 2x speed to save time, use time codes, and refer to additional resources in the description

Basic Concepts: Monomers and Polymers

• Monomers: Smaller units that can create larger molecules
  • Examples: Glucose, amino acids, nucleotides (RNA & DNA)
• Polymers: Made from monomers bonded together
  • Examples: Starch, cellulose, glycogen, proteins, DNA, and RNA
• Reactions: Condensation and Hydrolysis
  • Condensation Reaction: Joins two molecules, creating a chemical bond and removing water (3 marks in exams)
  • Hydrolysis Reaction: Breaks chemical bonds using water (3 marks in exams)

Carbohydrates

• Monosaccharides: 1 sugar unit
  • Examples: Glucose, fructose, galactose
• Disaccharides: 2 sugar units
  • Examples: Sucrose, maltose, lactose
• Polysaccharides: Many sugar units
  • Examples: Starch, cellulose, glycogen
• Alpha and Beta Glucose Structures:
  • Alpha glucose: C6H12O6, H on top, OH on bottom (carbon 1)
  • Beta glucose: OH on top, H on bottom (carbon 1)
• Glycosidic Bonds: Formed between monosaccharides via condensation reactions
• Polysaccharide Function and Structure:
  • Starch: Energy store in plants (alpha glucose)
  • Cellulose: Structural strength in plant cell walls (beta glucose)
  • Glycogen: Energy store in animals, particularly liver and muscle cells (alpha glucose)

Lipids

• Types: Triglycerides and phospholipids
• Structure: Both have glycerol; triglycerides have 3 fatty acids, phospholipids have 2 fatty acids and a phosphate group
• Formation: Condensation reactions forming ester bonds
• Fatty Acids: Saturated (no double bonds) vs. unsaturated (one or more double bonds)
• Functions:
  • Energy store (high carbon to hydrogen bond ratio)
  • Metabolic water source
  • Do not affect water potential due to insolubility
  • Light mass, useful for storage

Proteins

• Amino Acids: Monomers that make up proteins
  • Structure: Central carbon, hydrogen atom, R group, amino group (NH2), and carboxyl group (COOH)
• Protein Synthesis:
  • Primary Structure: Order of amino acids
  • Secondary Structure: Folding into alpha helices or beta sheets (hydrogen bonds)
  • Tertiary Structure: Further folding into 3D shapes (ionic, hydrogen, disulfide bonds)
  • Quaternary Structure: Multiple polypeptide chains

Enzymes

• Function: Catalyze reactions by lowering activation energy
• Specificity: Due to unique active site shape
• Models: Induced fit model (accepted model)
• Factors Affecting Rate: Temperature, pH, substrate concentration, enzyme concentration, inhibitors

Biochemical Tests

• Starch: Add iodine -> blue-black
• Reducing Sugars: Add Benedict’s reagent + heat -> green/yellow/orange/red
• Non-Reducing Sugars: Add acid, boil, neutralize, add Benedict’s + heat -> orange/red
• Proteins: Add Biuret solution -> purple
• Lipids: Dissolve in ethanol, add water -> white emulsion

DNA and RNA

• DNA: Contains genetic code
  • Structure: Double helix, complementary base pairs (A-T, C-G)
  • Replication: Semi-conservative, involving helicase and polymerase
• RNA: Almost identical to DNA but single-stranded and shorter
  • Types: mRNA, tRNA, rRNA
• ATP: Immediate energy source, composed of adenine, ribose, and three phosphates
  • Hydrolysis releases energy

Water Properties

• Metabolite: Involved in reactions
• Solvent: Due to polarity
• High Heat Capacity: Buffers temperature
• Large Latent Heat of Vaporization: Cooling effect
• Cohesion: Due to hydrogen bonds, important for transport in plants

Organelles and Their Functions

• Nucleus: Contains DNA, site of replication and transcription
• Endoplasmic Reticulum: Protein (rough ER) and lipid (smooth ER) synthesis
• Golgi Apparatus: Modifies and packages proteins
• Lysosomes: Contain digestive enzymes
• Mitochondria: Site of aerobic respiration (ATP production)
• Ribosomes: Protein synthesis
• Vacuole (Plants): Storage and turgidity maintenance
• Chloroplasts: Site of photosynthesis
• Cell Wall: Provides strength and prevents bursting in plants
• Plasma Membrane: Controls entry and exit
• Prokaryotic vs. Eukaryotic Cells: Key differences and structure

Cell Division and Microscopy

• Mitosis: Nuclear division producing two genetically identical diploid cells
• Meiosis: Produces four genetically different haploid gametes
• Binary Fission: Prokaryotic cell division
• Microscopy: Types (optical, SEM, TEM) and comparisons (resolution, magnification)
• Cell Fractionation: Isolating organelles through homogenization and ultracentrifugation

Immunity

• Self vs. Non-Self: Lymphocytes distinguish cells
• Phagocytosis: Non-specific response, macrophages engulf pathogens
• T and B Cells: Specific responses, including cell-mediated (T-cells) and humoral (B-cells)
• Antibodies: Structure and function in immune response
• Vaccines: Introducing antigens to create memory cells for immunity
• HIV Structure & Replication: Impact on the immune system
• Monoclonal Antibodies: Uses in treatment and diagnostics

Gas Exchange

• Human System: Alveoli structure and gas exchange
• Insects and Fish: Tracheal system and gills
• Plants: Gas exchange through stomata

Digestion and Absorption

• Carbohydrates: Enzymes like amylase break down into monosaccharides
• Proteins: Broken down by endopeptidases, exopeptidases, and dipeptidases
• Lipids: Digested by lipase and bile salts
• Absorption: Villi and microvilli increase absorption in intestine
• Co-Transport: Mechanism for glucose and amino acids

Transport in Plants and Animals

• Transpiration: Water movement and evaporation in plants
• Xylem and Phloem: Transport water and nutrients (cohesion-tension theory, translocation)
• Cardiovascular System: Heart structure, blood vessels, and blood flow
• Hemoglobin: Oxygen transport and dissociation curves

Biodiversity and Classification

• Genetic Diversity: Importance for species survival and adaptation
• Natural Selection: Mechanisms and types (directional, stabilizing)
• Species and Taxonomy: Organization and classification (hierarchy, binomial system)
• Measuring Biodiversity: Index of diversity, impact of human activities