Biology 11
Cell transport
Tan Liu
Company tour!
New protein graduates
Cell membrane
Transport department
What’s our department looks like?
Semi-permeable bilayer
structure
Head: Polar, hydrophilic
Tail: Non-polar, hydrophobic
What services do we do?
Passive
Active
Transport
Transport
Don’t requires energy
Energy involved!
Passive transport-Simple diffusion
e.g.: CO2; O2
1. No protein involved
1. High gradient towards low gradient
1. 2 conditions (size and polarity)
Passive transport- Facilitated diffusion
e.g.: H2O
1. Move from high to low
gradient
1. use specific protein
1. No energy cost
Active transport: Membrane pumps
e.g.: Sodium-potassium pump
1. Protein involved
1. ATP involved, using ATP
to change the
conformation of carrier
proteins
Active transport: Endocytosis and Exocytosis
1. Protein mediated
2. ATP required
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