Lecture Notes on Co-Transport

Introduction

• Co-Transport: A type of cell membrane transport involving a transport protein that moves two substances simultaneously.
• Not mentioned in the passive (diffusion, osmosis) or active transport, and bulk transport sections.
• Relevant in Chapter 7 (Plant Transport) and Chapter 14 (Homeostasis).

Key Concepts

What is Co-Transport?

• Involves a transport protein.
• Transports two substances across the cell membrane at the same time.
• Example: Hydrogen Ion-Sucrose Co-Transporter
  • Transports hydrogen ions and sucrose simultaneously.

Mechanism

• Phospholipid Bilayer: Part of the cell structure through which transport occurs.
• Transport Protein: Facilitates the co-transportation.
• Hydrogen Ion-Sucrose Co-Transporter:
  • Hydrogen ions represented as red dots.
  • Sucrose represented as green triangles.

Concentration Gradients

• Hydrogen ion concentration varies across the membrane.
• Focus on the first particle (hydrogen ion) in the transporter name.
  • Higher concentration on one side (Area A) than the other (Area B).
  • Hydrogen ions diffuse from high to low concentration through the co-transporter.
  • Sucrose follows hydrogen ions effortlessly.

Important Notes

• No ATP Required:
  • Even though sucrose moves from low to high concentration, it doesn't require ATP.
  • Movement is not active transport because sucrose accompanies the hydrogen ion.

Additional Information

• Symports and Antiports: Types of co-transporters.
  • Not necessary to memorize for exams.
• Understand that transport proteins can move two substances following the concentration gradient of one.

Summary

• Co-transport involves transport proteins moving two substances simultaneously.
• It follows the concentration gradient of one of the substances (e.g., hydrogen ions in hydrogen ion-sucrose transporter).
• No ATP is used in this process, differentiating it from active transport.

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Study Tip

• Focus on understanding the examples and the basic process of how co-transport works rather than memorizing specific details or definitions.