Membrane Structure and Function - 1.5 | Cell Theory | IB MYP Grade 12 Biology
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1.5 - Membrane Structure and Function

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Practice

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • The cell membrane is primarily composed of a phospholipid bilayer.

  • Proteins and carbohydrates in the membrane contribute to its function.

  • Selective permeability is essential for cellular homeostasis.

  • Passive and active transport regulate substance movement.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Passive Transport: Oxygen diffusing into a cell.

  • Facilitated Diffusion: Glucose entering cells via a carrier protein.

  • Active Transport: Sodium-potassium pump maintaining ion balance.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🧠 Other Memory Gems

  • PLiP – Phospholipids, Lipids, Proteins.

🎨 Fun Analogies

  • The membrane is like a security gateβ€”some enter freely, others need permission.

🎡 Rhymes Time

  • "A bilayer that's smart and keen, keeps the cell environment clean!"

Flash Cards

Review key concepts with flashcards.

Membrane Structure and Function

1. Phospholipid Bilayer

  • The fundamental structure of the membrane is the phospholipid bilayer.
  • Each phospholipid has a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails.
  • The bilayer arrangement ensures that hydrophobic tails are shielded from water, while heads face outward toward watery environments.

2. Fluid Mosaic Model

  • Describes the cell membrane as a dynamic, flexible structure.
  • "Fluid" refers to the lateral movement of phospholipids and proteins.
  • "Mosaic" reflects the patchwork of proteins, cholesterol, and carbohydrates embedded in or attached to the bilayer.

3. Membrane Proteins

  • Integral Proteins: Span the bilayer; involved in transport and signal transduction.
  • Peripheral Proteins: Attached to the surface; often involved in structural support and signaling.

4. Membrane Carbohydrates

  • Found on the extracellular side of the membrane.
  • Serve as recognition sites (e.g., for cell-cell communication or immune responses).

5. Selective Permeability

  • Allows specific molecules (e.g., O2, CO2, small lipids) to pass freely.
  • Others (e.g., ions, glucose) require protein channels or carriers.
  • Enables active and passive transport:
  • Passive Transport: Diffusion, osmosis, facilitated diffusion.
  • Active Transport: Requires ATP (e.g., sodium-potassium pump).