Active Transport Notes

Active Transport: requires additional input of energy (in the form of ATP)

  • Types: Pump Proteins, Bulk Transport —> Exocytosis & Endocytosis (Pinocytosis & Phagocytosis)

Passive Transport: does not require an additional input of energy ——> uses energy already present in the system in the form of molecular movement

  • EX: simple diffusion, facilitated diffusion, Osmosis

Pump Proteins:

Pump Proteins: transport proteins that move molecules/substances across a phospholipid bilayer against their concentration gradient

  • moves molecules from a low —> high concentration

  • must be transmembrane ——> requires additional input of energy (ATP)

  • EX #1: Proton Pumps —> pump H+ ions (protons) up a gradient (found in several different organelle membranes

  • EX #2: Sodium Potassium Pumps: pump Na+ out of the neuron & K+ ions into the neuron —> so an action potential can occur (found in nerve cells and others)

Exocytosis (Bulk Transport):

Exocytosis: bulk transport of material to be secreted/excreted out of the cell via vesicles

  • Exo-outside/external cyto-cell sis-process

  • Process: a vesicle (secretory or excretory) containing secretory or excretory material fuses w/ the membrane ——> vesicle contents are discharged to the extracellular space

    • excretory-waste products

    • secretory- “purposeful” materials, not waste

  • EX #1: Secretion of Glycolipids —> packaged into secretory vesicles by Golgi & fuses to the membrane

  • EX #2: Excretion of Wastes —> waste products/undigested food materials are excreted using exocytosis

  • EX #3: Secretion of neurotransmitters

Endocytosis:

Endocytosis: bulk transport of particles into the cell (Endo-inside/internal)

  • Process: cell membrane progressively invaginates (dips inward) & eventually engulfs the particles, pinching off ——> creating vesicle surrounding the engulfed particles

  • EX #1: Phagocytosis

  • EX#2: Pinocytosis

Phagocytosis: ingestion of large solid particles

  • phago = eating/devouring (“cellular eating”)

  • Process/EX: White Blood Cells (WBCs)

    • engulf pathogenic bacteria when fighting an infection

    • bacterium contained w/in a phagosome (food vacuole)

    • lysosome fuses w/ a phagosome to break down the bacterium (Hydrolysis)

Pinocytosis: ingestion of liquids

  • pino = to drink (“cellular drinking”)

  • Process: vesicle engulfs extracellular fluids/solutes —> the vesicles created are much smaller than the ones created in phagocytosis

Vesicles:

4 Types:

  1. Transport Vesicles: move materials w/in the cell

  2. Secretory Vesicles: store/transport materials to be secreted out of the cell

  3. Lysosomes: contain hydrolytic enzymes

  4. Peroxisomes: contain enzymes involved in detoxification & lipid metabolism

Clathrin: a protein that’s important to vesicle formation

  • creates a framework/cage to help form the vesicle

  • individual clathrin molecules come together to make a Clathrin-coated pit (CCP) ——> helps membrane invaginate & pinch off

  • vesicles created are clathrin-coated vesicles (CCV)

  • facilitates scission & disassembles after vesicle formation