Question 5

 

What is the current model for the molecular architecture of cell membranes and what are the various mechanisms by which substances cross cell membranes? [Chapter 8]

 

 

Membrane Structure (read pages 138-144)

 

  1. Models of membranes change to fit new data. The Davson-Danielli model has been replaced by the fluid mosaic model. Compare and contrast these two models.

 

  1. Membranes are fluid. Phospholipids and proteins can move laterally within the membrane. How is this possible?

 

  1. Membranes are mosaics of structure and function. Describe the components of the membrane and what their functions are.

 

  1. Membrane carbohydrates (oligosaccharides) are important for cell recognition.

 

Traffic Across Membranes (read pages 144-152)

 

  1. Membrane structure results in selective permeability

 

  1. Passive transport is diffusion across a membrane.

 

  1. Osmosis is the passive transport of water.

 

  1. Cell survival depends on balancing water uptake and loss.

 

  1. Specific proteins facilitate the passive transport of water and selected solutes.

 

  1. Active transport is the pumping of solutes against their gradients.

 

  1. Some ion pumps generate voltage across membranes.

 

  1. Cotransport couples the transport of two solutes.

 

  1. Exocytosis and endocytosis transport large molecules or particles. 

 

  1. Pinocytosis transports droplets of water.

 

 

 

 

John C. Murphy

           Science

Phone:  (815) 436-3200, ext. 2120

 

jmurphy@psd202.org

 


 

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