amazon.co.ukB2: Cell Structure, Transport and Immunology
Ultrastructure of eukaryotic and prokaryotic cells, fluid mosaic membranes, co-transport, cell-mediated and humoral immunity.
📋 Key Definitions and Core Concepts
Fluid Mosaic Model: Phospholipid bilayer with lateral mobility of lipids and embedded mosaic of transport/receptor proteins.
Antigen: A cell-surface glycoprotein or macromolecule that triggers an immune response.
🔍 Key Principles & Specification Requirements
- Transport: simple diffusion (small/non-polar), facilitated diffusion (channels/carriers), active transport (ATP against gradient), co-transport (Na⁺-glucose in ileum).
- Humoral immunity: B-cells differentiate into plasma cells producing specific monoclonal antibodies.
- Cell-mediated immunity: cytotoxic T-cells destroy virus-infected and cancerous cells via perforins.
💡 Worked Example Question
Exam-Style Question
Question:
Explain the co-transport of glucose in the mammalian ileum epithelium.
Model Solution & Mark Scheme:
1. Na⁺/K⁺ ATPase actively pumps Na⁺ out of epithelial cell into bloodstream, lowering intracellular [Na⁺]. 2. Na⁺ diffuses down gradient from lumen into cell via sodium-glucose co-transporters, dragging glucose against its gradient. 3. Glucose exits into capillary blood via facilitated diffusion.
❓ Practice Questions & Mark Schemes
Q1: Compare TEM and SEM electron microscopes.
Show Model Answer
Answer: TEM: transmits electrons through ultra-thin section (2D internal ultrastructure, 0.1 nm resolution). SEM: scans electron beam across surface (3D topography, 20 nm resolution).
Q2: Describe the role of memory B-cells in secondary immune response.
Show Model Answer
Answer: Memory B-cells circulate in blood; upon re-exposure to antigen, they rapidly divide into plasma cells producing high antibody titers before symptoms develop.
🎬 Video Resources
- Cell Structure, Transport and Immunology - Overview -- YouTube Search
- Cell Structure, Transport and Immunology - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
- AQA A-Level - Past Papers -- AQA
- Edexcel A-Level - Past Papers -- Edexcel
- OCR A-Level - Past Papers -- OCR
🔗 Further Reading & Resources
- Physics & Maths Tutor -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths -- Free resources, slides, and interactive questions
- BBC Bitesize -- BBC Bitesize revision resources