Levels of Organization & the Plasma Membrane Pt. 3 Flashcards
Membrane Transport
What are the 4 main categories of transport processes?
Bulk Flow; Diffusion; Protein-Mediated Transport; and Vesicular Transport.
Protein-Mediated Transport:
The majority of solutes transported across the membrane are in the form of protein mediated transport (b/c the solutes are either lipophobic or electrically charged)
- Requires a gradient (concentration, electrical, or pressure) as the driving force
What are the 2 sub-groups of Protein-Mediated Transport?
Channel Transporters
and Carrier Transporters
Channel Transporters
Channels with fluid filled chambers that have a direct link between the intracellular and extracellular compartments which allows very rapid transport of small ions and water across the membrane
- Can be open or gated channels
Channel Transporters: Open Channels (Leak Channels)
Channels with pores open at all times that allow molecules moving in and out without restriction
- the only contributing factor for the direction of flow (high->low) is the gradient
Second Messenger System
Intracellular messenger molecules (signal has to go off/be sent for the gates to be opened)
Channel Transporters: Gated Channels
Is in a closed state most of the time + movement of molecules can only occur when the gate is opened.
- the opening of the gates can be regulated by: second messenger system, chemically gated channels, voltage-gated channels, and mechanically gated channels.
Chemically Gated Channels
binds ligand to the extracellular receptor to open the gates (Ligand is the key and the receptor is the keyhole)
Voltage-Gated Channels
changes the electrical state of the membrane
Mechanically Gated Channels
Stimulation to the membrane in the form of pressure
Carrier Transporters
The 2nd sub-group of protein mediated transport.
there is no direct contact of the substrate between the intracellular and extracellular compartment at any given moment
- One end of the channel is always in a closing state
- slower than channel transporters (but can move bigger molecules)
Uniport
carriers that move only 1 kind of substrate
Symport
carriers that move more than 1 kind of substrates in the SAME direction
Antiport
Carriers that move more than 1 kind of substrates in the OPPOSITE direction
Facilitated Diffusion
a process where transported molecules move down their concentration gradient (similar to simple diffusion)
- No energy is required for the transport process
Active Transport
a process where transported molecules move AGAINST their concentration gradient (creates a state of disequilibrium)
- Requires ATP
- 2 types: Primary and Secondary
Primary (Direct) Active Transport:
A process that requires energy in the form of ATP to create a higher concentration gradient b/w intracellular and extracellular compartments.
(these primary active transporters are also known as ATPase)
Secondary (indirect) Active Transport
A process that uses the potential energy created by the primary active transport + convert them into kinetic energy for the transport of substrate against the concentration gradient
Vesicular Transport
A way of transporting macromolecules that are too large for the protein-mediated transport systems (ATP is required) by the means of endocytosis and exocytosis
Endocytosis
To internalize the macromolecules
3 types: Receptor-mediated Endocytosis, Phagocytosis, + Pinocytosis
Receptor-Mediated Endocytosis (type of endocytosis)
Also known as clathrin-mediated endocytosis
A highly selective process that requires a receptor. receptors for specific ligand are found on the extracellular surface of the membrane.
Phagocytosis (type of endocytosis)
Involves engulfing large solid particles via phagocytes (macrophages and neutrophils). The process begins when the particle binds to a plasma membrane receptor on the phagocyte.
- is non specific (engulf anything foreign)
- Eats the macromolecule using pseudopods
Pinocytosis (type of endocytosis)
Process that involves enclosing the extracellular fluid non-selectively + is also known as bulk-phase endocytosis (no receptor proteins are involved)
- Pino = “gobble it up with water”
Which transport process requires cytoplasmic vesicle to fuse with the plasma membrane, following by the secretion of vesicular contents into the extracellular fluid?
Exocytosis
