Page 42 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Movement across cell membranes

• Transport Mechanisms - moving material in and out of the cell

• Concentration gradient - the difference in the amount of a substance inside

and outside of the cell

1. Going “with the gradient”- moving from high to low concentration
2. Going “against the gradient”- moving from low to high concentration

3. Equilibrium exists when the concentration of molecules is the same inside
and outside the cell.

Types of Cellular Transport
A- Passive Transport

• Going with the gradient

• Cell doesn’t use energy

1- Diffusion
2- Facilitated diffusion

3- Osmosis

B- Active Transport
• Going against the

gradient

• Cell use energy

1- Protein pumps

2- Endocytosis
3- Exocytosis

C- Bulk transport

General Microbiology & Immunology (PM 401) theoretical handbook Page 31