Interaction and Interdependence: notes and practice questions
C. Interaction and interdependence (SL 31 h, HL 48 h). Components acting on each other. Enzymes and metabolism, respiration and photosynthesis at molecular level; chemical signalling (HL only) and neural signalling at cell level; body system integration and immunity at organism level; populations and energy flow at ecosystem level. This is the theme with the widest SL-to-HL gap, because respiration and photosynthesis both roughly double at HL. The hard parts are the biochemistry pathways at HL, the immune response sequence, and the statistics in C4.1 (Lincoln index, chi-squared). It is examined through graph interpretation, calculation, and sequenced outline items.
Subtopics
- Practice questionsEnzymes and Metabolism
This topic covers the role of enzymes as biological catalysts in metabolic pathways and the factors affecting their activity. Enzymes are globular proteins with specific active sites that bind to substrates via the induced-fit model.
- Practice questionsCell Respiration
This topic explores how cells release energy from carbon compounds to produce adenosine triphosphate (ATP). ATP is the energy currency of cells, used for processes like active transport, macromolecule synthesis, and cellular movement.
- Practice questionsPhotosynthesis
This topic explains photosynthesis as the transformation of light energy into chemical energy to produce carbon compounds. The overall word equation is: carbon dioxide + water glucose + oxygen.
- Practice questionsNeural Signalling
This topic covers neuron structure, electrical signal generation and propagation, and synaptic transmission. Neurons transmit electrical impulses along axons and dendrites.
- Practice questionsIntegration of Body Systems
This topic covers how different body systems coordinate and interact to maintain overall function and emergent properties in multicellular organisms. Body systems are organized hierarchically from cells to tissues, organs, and systems.
- Practice questionsDefence Against Disease
This topic explores how organisms defend against infectious diseases caused by pathogens. Primary defenses include physical barriers like skin and mucous membranes, and blood clotting.
- Practice questionsPopulations and Communities
This topic covers populations as interacting groups of the same species and communities as all interacting organisms in an ecosystem. Population size can be estimated using random quadrat sampling for sessile organisms or capture-mark-release-recapture for motile organisms.
- Practice questionsChemical SignallingHL only
This topic covers how cells receive and respond to chemical signals, focusing on the mechanisms of signal transduction and the diversity of signalling molecules and receptors. Receptors are proteins with specific binding sites for signalling chemicals, called ligands.
- Practice questionsTransfer of Energy and Matter
This topic explores the transfer of energy and the recycling of matter within ecosystems. Ecosystems are open systems, allowing both energy and matter to enter and exit.
