GCSE Biology: Organization Topic

Introduction

• Focus on organization topic in GCSE Biology.
• Includes exam questions and answers from various past papers (2018-2022).
• Document available for download to follow along.

Principles of Organization

• Key Question: Describe the relationship between cells, genes, DNA, and chromosomes.
  • Cells contain a nucleus.
  • Nucleus contains chromosomes.
  • Chromosomes are made of DNA.
  • Genes are sections of DNA coding for proteins.

Digestive System

• Role of Enzymes in Digestion:
  • Enzymes are biological catalysts.
  • Break down large insoluble molecules to small soluble molecules for absorption.
• Role of Bile:
  • Neutralizes stomach acid, optimizing pH for lipase.
  • Emulsifies fats, increasing surface area for enzyme action.
• Protease in the Stomach:
  • Works effectively in acidic conditions (low pH) provided by stomach acid.

Food Tests Required Practical

• Preparation:
  • Break food into small particles using pestle and mortar.
  • Mix with water (or ethanol for fats).
  • Filter to remove solids.
• Tests:
  • Starch: Iodine solution (turns blue-black if present).
  • Protein: Biuret solution (turns violet if present).
  • Fats: Sudan III test (red layer forms).
  • Sugars: Benedict's solution with hot water (turns orange).

Rates of Enzymes

• Effect of pH on Enzymes Practical:
  • Use buffer solution for constant pH.
  • Monitor starch breakdown with iodine.
• Protease in Baby Food:
  • Breaks down proteins into amino acids, making food softer for babies.

Human Circulatory System

• Levels of Organization:
  • Muscle cells, cardiac tissue, heart, circulatory system.
• Left Side of Heart:
  • Thicker to withstand higher pressure for systemic circulation.

Blood and Blood Vessels

• Artery vs Vein:
  • Arteries have thicker walls, narrower lumens, no valves.
  • Veins have valves, wider lumens.
• Double Circulatory System:
  • Blood pumped to lungs and body via separate pathways.

Ventilation and Gas Exchange

• Lung Adaptations:
  • Alveoli increase surface area.
  • Capillaries reduce diffusion path.
  • Good blood supply.

Non-Communicable Diseases

• Coronary Heart Disease Risk Factors:
  • Lack of exercise, obesity, smoking, stress, alcohol, poor diet.
• Cholesterol Blockers vs Statins:
  • Assess benefits and drawbacks.
• Pacemaker for Arrhythmia:
  • Regulates heartbeat.

Cancer

• Benign vs Malignant Tumors:
  • Benign are non-invasive.
  • Malignant can spread and invade.

Leaf Structure and Plant Processes

• Stomata Function:
  • Opens/closes to regulate gas exchange, water loss.
• Transpiration vs Translocation:
  • Transpiration: movement of water and minerals via xylem.
  • Translocation: movement of sugars via phloem.

Conclusion

• Comprehensive review of exam questions related to the organization topic in GCSE Biology.
• Emphasis on understanding concepts to apply in different contexts.