Membrane transport_ part 1.pdf

11/10/23 Membrane transport: 1 Structure and function of plasma and nuclear membranes: the material in made which 9 unionincludes living cons Continuous, surrounds the protoplasm. nudesand Plasma membrane: are cytoplasm Persists throughout the life of the cell Semi permeable Nuclear membrane: Discon...

11/10/23 Membrane transport: 1 Structure and function of plasma and nuclear membranes: the material in made which 9 unionincludes living cons Continuous, surrounds the protoplasm. nudesand Plasma membrane: are cytoplasm Persists throughout the life of the cell Semi permeable Nuclear membrane: Discontinuous with complex pores, surrounds the nucleus Disappears during cell division Regulated ow of material bet ween the nucleoplasm and the cytoplasm The membrane is a complex lipid based structure which forms pliable sheets of a variety of lipids and proteins. They separate the cell from it’s surroundings. The uidity is mainly determined by the fatty acid composition. Very few molecules can enter or leave the cell without the help of a protein. Only small non polar molecules can passively diffuse through. Passive diffusion of polar molecules requires de-salvation, this has a high activation barrier. Proteins that facilitate transport are called transporters or permeases. Even water movement is accelerated by the help of proteins. Example: blood brain barrier: Brain endothelial cells form the physical barrier. Function: Keeps out toxins Allows in essential nutrients Prevents brain penetration of over 98% of small compound drugs. Types of transport: Ionophores, ion channels and passive transporters simply speed transmembrane movement of solutes down their electrochemical gradients. Primary active transporters can pump solutes again their gradients using ATP Secondary active transports use the gradient of a second solute to provide the energy.