Membranes Function'

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Membranes Function. 1. Transport

• Simple diffusion.
• Channels and pores.
• Facilitated transport
• 1) Passive (incl. Gated pores)
• 2) Active

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A. Simple diffusion non-facilitated transport.

Always down a concentration gradient. No energy
required. Proteins not required. Rate is
proportional to concentration. Does not
saturate. Molecules diffuse through the lipid
bilayer. O2, CO2, lipid soluble vitamins. Not
specific.
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B. Pores and Channels.
Allows hydrophilic molecules to pass
through.
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Always from high to low concentration. Energy not
required. Proteins are required. Rate is
proportional to concentration. Does not
saturate. Not specific.
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Porin
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C. Facilitated transport 1) Passive 2) Active.
Both types Require proteins Are
specific Saturate (enzyme-like)
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3 types. Uniport
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Symport
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Antiport
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Gated pores.
Only some molecules can Fit through the gate.
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Passive no energy required high to low
concentration
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Passive Facilitative transport
Glucose transporter in Red blood cells (C F)
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Active Can go from a low to a high concentratio
n Requires energy - ATP
Two types. Primary Secondary
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Primary active transport. Bacteriorhodopsin Hydro
gen ion transport driven by electron
transport. Na-K ATPas
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Electron transport-driven proton transport.
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Na- K ATPase
K
Na
Requires energy
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Na-K-ATPase
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Secondary active transport. Energy provided by a
primary active transport pump.
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Electron-transport driven
primary proton transport.
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