Chapter 5.4 - Active Transport Flashcards
Why do some biological processes require active transport
Depend on presence of concentration gradient.
Maintain concentration gradient by moving particles up at faster rate than diffusion
Energy required
Active transport
Movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration. Requires energy and carrier proteins
Why is energy needed
Particles are being moved up a concentration gradient, opposite to diffusion
Where does energy come from
Metabolic energy supplied by ATP
What do carrier membranes do
Span membranes
Act as pumps
General process of active transport
1 - molecule/ion binds to receptors in channel of carrier protein on outside of cell
2 - on inside, ATP binds to carrier protein. hydrolysed to ADP and phosphate
3 - binding oh phosphate causes carrier protein to change shape opening up inside of cell
4 - molecule/ion released into cell
5 - phosphate molecule released and recombined with ADP to make ATP
6 - protein carrier returns to original shape
Describe process of carrier protein active transport
Selective as specific substances are transported by specific carrier proteins
Bulk transport
Active transport Large molecules (enzyme, bacteria) Too large to move through carrier and channel.
Endocytosis
Bulk transport into cell
Phagocytosis - solids
Pinocytosis - liquids
Cell surface membrane invaginates after contact is made
Membrane enfolds and forms vesicle around material
Vesicle pitches off into cytoplasm to transfer for further processing
Exocytosis
Vesicles formed by Golgi apparatus
Fuse with cell surface membrane
Contents released outside of cell
When is energy from ATP required
Movement of vesicle along cytoskeleton
Changing shape of cells to engulf materials
Fusion of cell membranes as vesicles form
