IGCSE Edexcel Biology Lecture Notes

Introduction

• Welcome to the IGCSE Edexcel Biology video (9-1)
• Covers every specification point for achieving a grade 9
• Mention of revision guides available at www.sciencewithhazel.co.uk

Features of Living Organisms

• Mrs Nerg/Mrs Gren:
  • Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction, Growth
• Viruses are non-living, e.g., they do not move, respire, or excrete

Basic Cell Biology

Animal and Plant Cells

• Shared organelles: Cell membranes, cytoplasm, nucleus, ribosomes, mitochondria
• Plant-specific organelles: Cell wall (cellulose), vacuole (cell sap), chloroplasts (chlorophyll)

Cell Functions

• Nucleus: Controls cell activities
• Cytoplasm: Site of chemical reactions
• Cell Membrane: Regulates entry/exit
• Ribosomes: Site of protein synthesis

Types of Cells

• Eukaryotes: Animal cells, contain membrane-bound organelles
• Prokaryotes: Viruses and bacteria, no membrane-bound organelles

Bacterial Cell Structure

• Features: Cell wall, slime capsule, flagellum, nucleoid, plasmids
• Pathogens vs. non-pathogenic bacteria

Viruses

• Smaller than bacteria, consist of protein coat and DNA or RNA
• Always pathogenic, examples: flu, cold, HIV

Protoctists and Fungi

Protoctists

• Varied organisms, e.g., algae (plant-like) and amoeba (animal-like)

Fungi

• Similar to plant cells but have chitin cell walls
• Examples: Mucor, mushrooms, yeast

Biological Classification

• Five kingdoms: Plants, Animals, Protoctists, Bacteria, Fungi
• Storage of carbohydrates: Animals (glycogen), Plants (starch), Fungi (glycogen)

Organization within Organisms

• Cell: Group of organelles
• Tissue: Group of cells
• Organ: Group of tissues
• Organ System: Group of organs
• Organism: Group of organ systems

Digestive System Overview

• Organs: Stomach, esophagus, pancreas, small and large intestines
• Tissues in Stomach: Glandular tissue secretes acid; muscular tissue churns food

Stem Cells and Differentiation

• Differentiation: Cells become specialized
• Types of stem cells: Embryonic (can become any cell), Adult (limited to one type)

Enzymes

• Biological catalysts, have active sites for substrate binding
• Digestive Enzymes: Amylase (starch to glucose), Protease (proteins to amino acids), Lipase (fats to fatty acids and glycerol)
• Temperature and pH: Affect enzyme activity

Transport Mechanisms

• Diffusion: Passive movement from high to low concentration
• Osmosis: Net movement of water across a semi-permeable membrane
• Active Transport: Movement against concentration gradient requiring energy

Plant Processes

Photosynthesis

• Takes place in chloroplasts; produces glucose and oxygen
• Limiting factors: Carbon dioxide, light intensity, temperature

Leaf Structure

• Adaptations for photosynthesis: Large surface area, thin structure, waxy cuticle, palisade mesophyll

Transpiration

• Loss of water vapor from leaves, affected by humidity, temperature, wind, and light

Human Digestive System

• Mechanical (chewing, churning) vs. Chemical digestion (enzymes)
• Bile: Emulsifies fats, neutralizes stomach acid

Balanced Diet and Nutrients

• Nutrients: Carbohydrates, proteins, fats, vitamins, minerals, water, fiber
• Deficiency diseases like scurvy (vitamin C) and rickets (vitamin D)

Respiration

• Aerobic: Uses oxygen, produces CO2, water, and energy
• Anaerobic: Occurs without oxygen, produces lactic acid (in muscles) or ethanol (in yeast)

Breathing System

• Structure: Trachea, bronchi, bronchioles, alveoli
• Ventilation: Inhalation increases thorax volume, exhalation decreases it

Circulatory System

• Heart Structure: Left/right atria and ventricles, valves
• Double Circulation: Blood passes heart twice per cycle

Blood Components

• Red blood cells (oxygen transport), white blood cells (immune response), plasma (carries nutrients), platelets (clotting)

Immune System

• Phagocytes: Engulf pathogens
• Lymphocytes: Produce antibodies
• Vaccinations: Introduce antigens to produce immunity

Plant Transport

• Xylem: Water and minerals upwards
• Phloem: Sugars in both directions

Human Excretory System

• Kidneys: Filter blood, produce urine
• Osmoregulation: Control of water content using ADH

Coordination and Response

Plants

• Tropisms: Responses to stimuli (light, gravity)
• Auxins: Plant hormones affecting growth direction

Humans

• Nervous System: Electrical impulses for communication
• Hormonal Communication: Chemical messengers in blood

Eye Structure and Function

• Cornea: Refracts light
• Lens: Focuses light on the retina
• Pupil Reflex: Adjusts pupil size based on light

Homeostasis

• Skin: Thermoregulation, protection
• Responses to cold/hot environments

Genetic Concepts

• Genome, Gene, Alleles: Definitions and roles
• DNA Structure: Double helix, bases (A, T, C, G)
• RNA Differences: Single-stranded, uracil instead of thymine
• Protein Synthesis: Transcription and translation processes

Inheritance Patterns

• Dominant vs. Recessive: Traits requiring one or two alleles
• Punnett Squares: Predicting offspring genetic outcomes
• Pedigree Analysis: Understanding inheritance from family trees

Cell Division

• Mitosis: Produces identical cells for growth and repair
• Meiosis: Produces varied gametes for sexual reproduction

Ecology and Environment

• Carbon Cycle: Photosynthesis, respiration, decomposition
• Nitrogen Cycle: Nitrates, nitrogen fixation, denitrification
• Human Impact: Eutrophication, greenhouse effect, acid rain

Genetic Engineering

• GMOs: Transgenic organisms for desired traits
• Insulin Production: Using bacteria to produce human hormones

These notes summarize the key points covered in the lecture, providing a comprehensive overview of IGCSE Edexcel Biology topics.