Learning Objectives
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# Learning Objectives - Understand what biological networks represent - Know different types of biological networks - Appreciate the network perspective in biology ## 1. What Are Biological Networks?
Learning Objectives
- Understand what biological networks represent
- Know different types of biological networks
- Appreciate the network perspective in biology
1. What Are Biological Networks?
Living systems are complex networks of interacting molecules. Network biology represents these as graphs: nodes = biological entities, edges = interactions.
Why Network Perspective? Reveals system-level properties not visible from individual components. Identifies key players (hubs, bottlenecks). Predicts functions of unknown genes/proteins.
2. Types of Biological Networks
| Network | Nodes | Edges | Scale |
|---|---|---|---|
| Protein-Protein Interaction (PPI) | Proteins | Physical binding | ~20k nodes |
| Gene Regulatory Network (GRN) | Genes + TFs | Regulatory | ~20k nodes |
| Metabolic Network | Metabolites | Reactions | ~5k nodes |
| Signaling Network | Proteins | Signal transduction | ~2k nodes |
| Co-expression Network | Genes | Expression correlation | ~20k nodes |
3. Graph Representations
Undirected (PPI), Directed (GRN), Weighted (co-expression), Bipartite (drug-target).
Q1: Why study biology from a network perspective?Biological systems are highly interconnected. Understanding individual components doesn't explain system behavior. Networks reveal how components work together, which are critical, how disruptions cause disease. Q2: What is the difference between PPI and GRN?PPI: physical binding (undirected, stable/transient). GRN: regulatory (directed, causal). PPI links proteins; GRN links TFs to regulated genes. Q3: What is a bipartite network in biology?Two types of nodes, edges only between types. Example: drug-target network where drugs connect to targets but not to other drugs. Q4: How do co-expression networks differ from PPI?Co-expression: edges = correlation (inferred, functional). PPI: edges = physical binding (experimental). Co-expression easier to measure globally but noisier. Join Discord NextNetwork Properties & Metrics