IGCSE Biology Video 91 Lecture Notes

Introduction

• Lecture is an all-in-one guide for IGCSE Biology.
• Aims to cover every specification point for confidence in exams.
• Mention of available revision guides online.

Shared Features of Living Organisms

• MRS. NERG: Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction, Growth.
• Non-living things like viruses do not exhibit these functions.

Basic Cell Biology

• Animal & Plant Cells Share: Cell membranes, cytoplasm, nucleus, ribosomes, mitochondria.
• Plant Cell Specific Organelles: Cell wall, vacuole, chloroplasts.
• Functions:
  • Nucleus: Control center of cell activities.
  • Cytoplasm: Site of chemical reactions.
  • Cell membrane: Regulates entry and exit of substances.
  • Ribosomes: Protein synthesis.
  • Cell wall (plant): Structure and protection.
  • Vacuole (plant): Maintains cell structure.
  • Chloroplasts (plant): Site of photosynthesis.

Eukaryotes vs. Prokaryotes

• Eukaryotes: Cells with membrane-bound organelles (e.g., animal cells, plants).
• Prokaryotes: Cells without membrane-bound organelles (e.g., bacteria, viruses).
• Bacterial Cells: Contain cell wall, sometimes slime capsule or flagella, no distinct nucleus, plasmids.

Pathogens

• Pathogenic Bacteria: Pneumococcus (pneumonia), Tuberculosis (TB).
• Useful Bacteria: Lactobacillus bulgaricus (yogurt production).
• Viruses: Non-living, always pathogenic (examples: flu virus, HIV).

Protists

• Algae & Chlorella: Plant-like with chloroplasts.
• Amoeba: Animal-like, no chloroplasts.
• Plasmodium: Pathogenic, causes malaria.

Fungi

• Structure: Similar to plant cells but no chloroplasts, cell wall made of chitin.
• Nutrition: Saprotrophic nutrition, secreting enzymes on dead matter.
• Uses: Yeast in beer and bread making, anaerobic respiration produces ethanol and CO2.

Classification and Storage

• Five Kingdoms: Plants, Animals, Protists, Bacteria, Fungi.
• Carbohydrate Storage: Glycogen in animals and fungi, starch in plants.

Organization in Organisms

• Definitions: Cell, Tissue, Organ, Organ System, Organism.
• Digestive System Example: Organs - Stomach, esophagus, pancreas, intestines.

Reproduction and Growth

• Zygote: Formed from fertilization between sperm and egg.
• Enzymes: Biological catalysts with active sites.

Enzymes in Digestion

• Amylase: Breaks down starch to glucose.
• Protease: Breaks down proteins to amino acids.
• Lipase: Breaks down lipids to fatty acids and glycerol.

Enzyme Activity

• Factors: Temperature, pH.
• Denaturation: Enzymes lose function beyond optimal conditions.

Transport Mechanisms

• Diffusion, Osmosis, Active Transport.
• Amoeba: Uses diffusion due to large surface area to volume ratio.

Photosynthesis and Leaves

• Photosynthesis Equation: Carbon dioxide + Water → Glucose + Oxygen.
• Limiting Factors: Light, temperature, carbon dioxide.
• Leaf Structure: Adaptations for photosynthesis.

Plant and Human Nutrition

• Mineral Ions: Nitrates and magnesium absorbed by active transport.
• Deficiency Symptoms: Yellow leaves (lack of magnesium), stunted growth (lack of nitrates).

Human Digestion

• Processes: Mechanical and chemical digestion.
• Enzymes: In the mouth, stomach, and intestines.
• Bile: Emulsification and neutralization of stomach acid.

Balanced Diet and Nutrients

• Nutrients Needed: Carbohydrates, proteins, fats, minerals, vitamins, water, fiber.
• Vitamin and Mineral Deficiencies: Scurvy (vitamin C), rickets (vitamin D), anemia (iron).

Respiration

• Aerobic Respiration Equation: Oxygen + Glucose → Carbon Dioxide + Water + Energy.
• Anaerobic Respiration: In muscles during strenuous exercise, produces lactic acid.

Circulatory System

• Heart Structure: Four chambers, double circulatory system.
• Blood Flow: Oxygenated and deoxygenated pathways.
• Blood Components: Red blood cells, white blood cells, plasma, platelets.

Lungs and Breathing

• Breathing Process: Inhalation and exhalation mechanics.
• Alveoli: Gas exchange surface area, thin walls for diffusion.

Excretion

• In Plants: Release of oxygen and carbon dioxide.
• In Humans: Sweat, urea, carbon dioxide.

Coordination and Response

• Homeostasis: Maintaining steady internal environment.
• Human Nervous System: Stimulus, receptor, response pathway.
• Hormones: Chemical messengers in the blood.

Reproduction

• Sexual vs. Asexual Reproduction: Genetic variation vs. genetic uniformity.
• Human Reproductive Systems: Structure and function of male and female systems.

Protein Synthesis

• DNA and Genes: Genotype, phenotype, alleles.
• Punnett Squares: Predicting offspring traits.

Genetic Engineering

• Applications: Production of insulin, GM plants.
• Processes: Use of plasmids as vectors, restriction and ligase enzymes.

Ecology

• Community and Ecosystem Definitions: Components and interactions.
• Food Chains and Webs: Energy flow, trophic levels, pyramids of numbers and biomass.

Human Impact on the Environment

• Eutrophication: Effects of fertilizers and sewage.
• Greenhouse Effect: Global warming causes and effects.
• Acid Rain and Pollution: Sources and environmental impacts.

Biological Resources Management

• Agricultural Practices: Greenhouses, fertilizers, pesticides.
• Fermenters: Use in microbial growth and production.
• Selective Breeding: Methods and benefits in agriculture.

Conclusion

• Encouragement to use revision guides for further study.