Home / IB DP Biology- C3.2 Defense against disease- IB Style Questions For HL Paper 2

IB DP Biology- C3.2 Defense against disease- IB Style Questions For HL Paper 2 -FA 2025

IBDP Biology HL Paper 2 -FA 2025- All Chapters

Question

Emergent properties arise when multiple components of a multicellular organism—such as cells, tissues, organs, and organ systems—work together in an integrated way.
(a) Outline how cell organelles coordinate their functions to synthesize and secrete proteins.
(b) Describe how different muscles act together to achieve inhalation in the lungs.
(c) Explain how various blood cells work cooperatively to generate adaptive immunity.

Most-appropriate topic codes (CED):

• TOPIC B2.2: Organelles and compartmentalization — part (a)
• TOPIC B3.1: Gas exchange — part (b)
• TOPIC C3.2: Defence against disease — part (c)
▶️ Answer/Explanation
Detailed solution

(a)
Protein production and secretion involve coordinated activity among several organelles:
1. Nucleus: Contains DNA and produces mRNA containing the gene instructions for the protein.
2. Ribosomes/Rough ER: Ribosomes on the rough endoplasmic reticulum (RER) translate the mRNA into a polypeptide. The RER encloses these proteins in transport vesicles.
3. Golgi apparatus: Vesicles fuse with the Golgi, where proteins are processed, modified, and packaged for secretion.
4. Vesicles/Plasma membrane: Secretory vesicles travel to the membrane and release proteins through exocytosis.

(b)
Inhalation occurs through the coordinated contraction and relaxation of muscles:
1. The diaphragm contracts, flattening and moving downward.
2. The external intercostal muscles contract, lifting the ribcage upward and outward.
3. The internal intercostal muscles relax, allowing rib expansion.
4. These actions increase thoracic volume and reduce lung pressure, drawing air into the lungs.

(c)
Adaptive immunity relies on coordinated interactions between blood cells:
1. Antigen presentation: Macrophages ingest pathogens and display antigens on their surface.
2. Helper T-cell activation: A helper T-cell binds to the antigen-presenting macrophage and becomes activated.
3. B-cell activation: Activated helper T-cells stimulate specific B-cells to divide and differentiate.
4. Antibody production: Activated B-cells become plasma cells, which release antibodies targeting the pathogen.
5. Memory cell formation: Some B-cells and T-cells differentiate into memory cells, enabling a much faster response if the same pathogen infects again.

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