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A-Level Biology Complete Guide
Jul 9, 2024
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Review flashcards
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
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