1.4 - Membrane Transport Flashcards
What allows vesicles to be constructed, moved around, and then deconstructed?
The fluidity of membranes, which allows structures surrounded by a membrane to change shape and move
What carries out the formation of a vesicle?
Proteins in the membrane, using energy from ATP
Describe endocytosis
Vesicle is formed by pinching off a small piece of the plasma membrane of cells
Vesicle is formed on the inside of the plasma membrane
Vesicle contains material that was outside the cell, so this is a method of taking materials into the cell
What do vesicles taken in by endocytosis contain?
Water and solute a from outside the cell, but they also contain larger molecules needed by the cell that cannot pass across the plasma membrane
Example of substances in vesicles which are passed across through endocytosis in humans
In the placenta - proteins from the mothers blood, including antibodies, are absorbed into the fetus by endocytosis
What do vesicles move?
The contents of the vesicles
Proteins in the membrane of the vesicle
Process of moving vesicle contents in secretory cells
Protein is synthesized by ribosomes on the rER and accumulates inside the rER
Vesicles containing the proteins bud off the rER and carry them to the Golgi apparatus
The vesicles fuse with the Golgi apparatus, which processes the protein in its final form
Vesicles bud off the Golgi apparatus and move to the plasma membrane, where the protein is secreted
Process of vesicle movement in growing cells
In a growing cell, the area of the plasma membrane needs to increase
Phospholipids are synthesized next to the rER and become inserted into the rER membrane
Ribosomes on the rER synthesized membrane proteins which also become inserted into the membrane
Vesicles bud off the rER and move to the plasma membrane
They fuse with it, each increasing the area of the plasma membrane by a very small amount
This method can also be used to increase the size of organelles in the cytoplasm such as lysosomes and mitochondria
Describe exocytosis
When a vesicle fuses with the plasma membrane, the contents are then outside the membrane therefore outside the cell
Describe the process of digestive enzymes being released from gland cells by exocytosis
The polypeptides in the enzymes are synthesized by the rER
Polypeptides are processed in the Golgi apparatus, and then carried to the membrane in vesicles for exocytosis
In this case - release is called ‘secretion’, because a useful substance is being released, not a waste product
What are the 4 methods of moving particles across membranes?
Simple diffusion
Facilitated diffusion
Osmosis
Active transport
What is diffusion?
The spreading out of particles in liquids and gases that happens because the particles are in continuous random motion
