Learn Novel Biology: Transport Across Membranes

Introduction

• Today's session covers active transport and Co-transport across membranes.
• Recap from GCSE and A-level knowledge of membrane transport.

Types of Transport Across Membranes

1. Simple Diffusion
   • Movement down concentration gradient.
   • Does not involve a protein.
2. Facilitated Diffusion
   • Movement down concentration gradient through a protein.
3. Active Transport
   • Movement against concentration gradient through a protein.
   • Requires energy (ATP).

Active Transport

• Movement from low to high concentration through a carrier protein.
• Requires ATP as it moves against the gradient.
• Transport Process:
  1. Carrier Proteins: Specific to certain molecules that fit receptor sites.
  2. ATP Interaction: ATP attaches and hydrolyzes to ADP, with phosphate attaching to carrier protein.
  3. Protein Shape Change: Causes release of ions (sodium example) to the other side.
  4. Phosphate Release: Restores protein to original shape.

Co-Transport

• Example: Co-transport of Glucose and Sodium Ions in the Ileum.
• Why Co-Transport: High glucose concentration in epithelial cells requires active transport from the ileum.

Steps in Co-Transport Process

1. Active Transport of Sodium Ions:
   • Sodium ions moved from epithelial cells to the blood, lowering sodium concentration inside cells.
   • Facilitates sodium movement from lumen to cells by facilitated diffusion.
2. Co-transport Protein:
   • Sodium ions bind to a co-transporter protein, facilitating glucose attachment.
   • Both ions and glucose transported together across membrane.
3. Facilitated Glucose Diffusion:
   • High glucose concentration moves into blood by facilitated diffusion.
   • Blood flow maintains concentration gradient.

Additional Details

• Microvilli: Increase surface area, aiding in absorption.
• Flowing Blood: Prevents glucose buildup by constant circulation.

Summary

• Active Transport: Moves molecules through a membrane with ATP.
• Co-Transport: Type of active transport; involves glucose and amino acids moving from ileum to bloodstream.

Conclusion

• Practice questions available at Miss Ester's site.
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