Make a concept map of Cellular Transport Mechanisms for small and large molecules. Include the terms, biological membrane, active transport, passive transport; facilitated transport, simple diffusion, osmosis, exocytosis, endocytosis, membrane potential and other key terms in this chapter.
The Correct Answer and Explanation is:
✅ Concept Map: Cellular Transport Mechanisms
scssCopyEdit ┌────────────────────────────┐
│ **Cellular Transport** │
└────────────┬───────────────┘
│
┌────────────────────────────────────┴────────────────────────────────────┐
│ │
┌────────────────────────────┐ ┌────────────────────────────┐
│ **Passive Transport** │ │ **Active Transport** │
└────────────┬───────────────┘ └────────────┬───────────────┘
│ │
┌────────────┴────────────┐ ┌────────────┴────────────┐
│ Simple Diffusion │ │ Carrier Proteins │
│ (small, nonpolar) │ │ (use ATP) │
├─────────────────────────┤ ├─────────────────────────┤
│ Osmosis (H₂O) │ │ Sodium-Potassium Pump │
└─────────────────────────┘ └─────────────────────────┘
│ │
▼ ▼
┌────────────────────────────┐ ┌────────────────────────────┐
│ **Facilitated Diffusion** │ │ **Bulk Transport** │
│ (via channel/carrier) │ └────────────┬───────────────┘
└────────────┬──────────────┘ │
▼ ▼
┌──────────────────────┐ ┌────────────────────┐
│ Membrane Proteins │ │ Endocytosis │
└────────────┬─────────┘ │ (into cell) │
▼ ├────────┬───────────┤
┌──────────────────────┐ │Phagocytosis│Pinocytosis│
│ Membrane Potential │ └──────┬─────┘
│ (ion gradient) │ ▼
└──────────────────────┘ ┌────────────────────┐
│ Exocytosis │
│ (out of cell) │
└────────────────────┘
📘 Explanation
Cellular transport refers to the movement of substances across the biological membrane—a selectively permeable lipid bilayer that regulates what enters and exits the cell. This process is essential for maintaining homeostasis, acquiring nutrients, removing wastes, and communicating with the environment.
Transport mechanisms are broadly classified into passive and active transport.
Passive transport does not require energy and occurs due to concentration gradients. It includes:
- Simple diffusion, where small, nonpolar molecules (like oxygen and carbon dioxide) move directly across the membrane.
- Osmosis, a special case of diffusion involving water molecules through a semi-permeable membrane.
- Facilitated diffusion, where larger or polar molecules (like glucose or ions) cross the membrane via specific channel or carrier proteins.
Active transport, on the other hand, requires energy, usually in the form of ATP, because substances move against their concentration gradients. Examples include the sodium-potassium pump, which moves Na⁺ out and K⁺ into the cell, establishing a membrane potential (an electrical gradient across the membrane).
For transporting large molecules, the cell uses bulk transport mechanisms:
- Endocytosis is the process of taking materials into the cell. This includes phagocytosis (cell “eating” solid particles) and pinocytosis (cell “drinking” fluids).
- Exocytosis expels materials like waste or hormones by fusing vesicles with the membrane.
Together, these transport systems enable cells to function properly by controlling their internal environment and responding to external changes effectively.
