BIOL 2021 Lecture Notes - Lecture 2: Membrane Transport Protein, Nuclear Pore, Potassium Channel
19 Jan 2018
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Document Summary
Membrane is permeable to small, nonpolar molecules oxygen, nitrogen, etc: hydrophobic molecules can go through, sometimes water, glucose and sucrose are hard to get through. Smaller the molecules, & the less strongly it associates with water, more rapidly the molecule will diffuse across the bilayer. Highly impermeable to ions cant go through the membrane without assistance. Cells use membrane transport proteins to: ingest nutrients glucose, excrete waste urea, regulate ion concentrations. Transport needs to occur across plasma membrane as well as internal organelle membranes. Ions and small molecules and sugars transport protein. Macromolecules (proteins, mrna) protein translocators and nuclear pores. Large particles or engulfing other cells endocytosis and phagocytosis. Ion gradients exist across membranes there are concentration differences b/t inside & outside the cell. There"s excess of negative charge inside cell which is why there is a negative membrane potential. Membrane potential spans from -20mv to -150mv. Work is proportional to the electrical and chemical parts together.
