Active Transport...Proton Pump (video link –please watch –1:04)•Moves protons (H+) against the...
Transcript of Active Transport...Proton Pump (video link –please watch –1:04)•Moves protons (H+) against the...
Active Transport
Topics 2.6 and 2.9
Active Transport Overview
• Requires free energy (ATP) to move molecules
Active Transport: Membrane Pumps
• Uses membrane proteins embedded in the membrane to move solutes against their gradients
• Allows cells to maintain concentration gradients that differ from their surroundings
• Some pumps establish and maintain membrane potentials (voltage)
• Examples: sodium-potassium pump, proton pump
Factors Affecting Cellular Transport
• Chemical driving force
• Electrical driving force
• Electrochemical driving force (combination)
Sodium-Potassium Pump(video link – please watch – 2:26)
• Pumps sodium ions (Na+) out of the cell and potassium ions (K+) into the cell
• Regulates osmolarity of cytosol by controlling the solute concentration inside the cell
• Maintains and restores the resting potential of cells, such as neurons, cardiac and kidney
• Primary pump in animal cells
Nerve Cell Signaling(video link – please watch – 2:52)
Proton Pump(video link – please watch – 1:04)
• Moves protons (H+) against the concentration gradient in order to generate a proton gradient across the membrane
• Used in the synthesis of ATP during cellular respiration
• Causes changes in pH
Active Transport: Bulk Transport
• Involves changes in the membrane structure
• Transports macromolecules (proteins, polysaccharides, etc.) by packaging the materials into vesicles
Exocytosis
• Cell secretes large molecules by fusion of the vesicles with the cell membrane
Exocytosis Example
• Release of neurotransmitters between neurons
Endocytosis• Region of the cell membrane sinks inward and
pinches off to form a vesicle to bring extracellular material into the cell
Endocytosis: Phagocytosis
• Cells engulf large particles or other cells using pseudopods
• Example: white blood cell consuming bacteria, ameba consuming food
Endocytosis: Pinocytosis
• Droplets of extracellular fluid are taken into the cell in small vesicles
• Example: Uptake of nutrients by the microvilliof the small intestine
Receptor-Mediated Endocytosis
• Enables cells to acquire specific substances from extracellular fluid
• Molecules bind to receptors
• Example: cholesterol uptake from the blood
Review of Cellular Transport(video link – please watch – 4:44)