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Alberts • Johnson • Lewis • Morgan • Raff • Roberts • Walter

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1 Alberts • Johnson • Lewis • Morgan • Raff • Roberts • Walter
da Alberts • Johnson • Lewis • Morgan • Raff • Roberts • Walter Molecular Biology of the Cell Sixth Edition con integrazioni e modifiche Chapter 11 Membrane Transport of Small Molecules and the Electrical Properties of Membranes Copyright © Garland Science 2015


3 Ion concentration is different inside and outside cells

4 Synthetic lipid bilayers have different permeability to different classes of molecules

5 Permeability coefficients of different molecules are very different

6 The two main classes of membrane transport proteins are: transporters and channels

7 Transport across membranes can be:
Passive or Active

8 The electrochemical gradient affects ion transport


10 Conformational changes of a transporter can mediate passive transport

11 Transporter-mediated diffusion reaches a maximum

12 Active transport is carried out in three main ways

13 Transporters can transfer one ion or two ions, in the same or in the opposite direction

14 Glucose transport is driven by Na gradient
Ion gradients represent an energy source

15 Glucose crosses the intestinal epithelium

16 There are three types of ATP-driven pumps

17 ER calcium pump is a P-type transporter

18 Na-K ATPase is also a P-type pump

19 ABC transporters are the largest family of membrane transport proteins


21 Water crosses the membrane through channels: the aquaporins

22 Channels can have a closed or open conformation

23 Channels can be regulated by several mechanisms

24 Ion distribution determines membrane potential

25 Channel structure determines ion selectivity

26 Mechanosensitive channels open and close

27 Ion transport is fundamental for nerve cell function

28 Sodium channels have a key role in the generation of a membrane potential

29 Individual ion channels can be monitored by patch clamp

30 Release of neurotransmitter occurs at synapses

31 Various channels are activated in sequence at the neuromuscular junction

32 Single neurons are complex computation devices


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