12: Membranes and Membrane Proteins
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- 12.1: Basic Concepts in Membranes
- The orderly movement of compounds through cell membranes is critical for the cell to be able to 1) get food for energy; 2) export materials; 3) maintain osmotic balance; 4) create gradients for secondary transport; 5) provide electromotive force for nerve signaling; and 6) store energy in electrochemical gradients for ATP production (oxidative phosphorylation or photosynthesis). In some cases, energy is required to move the substances (active transport).
- 12.2: Membrane Bilayer and Monolayer Assemblies - Structures and Dynamics
- Fatty acids can be saturated (contain no double bonds in the acyl chain), or unsaturated (with either one -monounsaturated - or multiple - polyunsaturated - double bond(s)).
- 12.4: Transport in Membranes
- It is essential for cells to be able to uptake nutrients. This function along with movement of ions and other substances is provided by proteins/protein complexes that are highly specific for the compounds they move. Selective movement of ions by membrane proteins and the ions’ extremely low permeability across the lipid bilayer are important for helping to maintain the osmotic balance of the cell and also for providing for the most important mechanism for it to make ATP - the process of oxidat
- 12.6: Membranes and Membrane Proteins
- One easily understandable function of membrane bilayers is to separate the inside and outside of the cell or intracellular organelles. Yet as we mentioned before, such barriers can not be so rigid and impenetrable that they prevent movement of materials across the membrane. Let's turn our attention to proteins that associate with the membrane and confer added functionalities to it.