Active Transport: Protein-Mediated Movement Up the Gradient Flashcards
How does active transport differ from facilitated diffusion?
active transport makes it possible to move solutes up a concentration gradient, or against an electrochemical gradient (away from equilibrium)
active transport always requires?
an input of energy
active transport couples…
endergonic transport to an exergonic process, usuallu ATP hydrolysis
Active transport performs three important cellular functions..
- uptake of essential nutrients
- removal of waste
- maintenance of non equilibrium concentrations of certain ions
active transport allows..
the creation and maintenance of an internal cellular environment that differs greatly from the surrounding environment
in active transport, diffusion is non directional with respect to the membrane…
diffusion is directed by concentrations of the transported substances. ie active transport have an intrinsic directionality
examples of active transport?
- Na+/K+ pump in animal cells
- The Na+/glucose symporter
- Light driven proton transport
How can active transport mechanisms be divided? What are the different mechanisms?
Can be divided based on the sources of energy and whether or not two solutes are transported at the same time. Either direct or indirect
What is indirect active transport?
the accumulation of solute molecules or ions on one side of the membrane is coupled directly to an exergonic chemical reaction, most commonly the hydrolysis of ATP
indirect active transport:
transport proteins driven directly by ATP hydrolysis are called..
transport ATPases, or ATPase pumps
direct active transport depends on…what are the differences and what are the similarities?
Four types of transport ATPases, which differ in size, structure, mechanism, locomotion, and roles, all use the energy of ATP hydrolysis to transport solutes against a concentration gradient or electrochemical potential
What are the four types of transport ATPases used in direct active tranport?
- P-type ATPase (P for phosphorylation)
- V-type ATPase ( V for vacuole)
- F-type ATPase ( F for factor)
- ABC-type/ATP Binding Cassette transporters
How do P-type ATPases work in direct active transport?
P-type ATPases are reversibly phosphorylated by ATP as part of the transport mechanism, with a specific aspartic acid residue becoming phosphorylated in each case
structure of P-Type ATPases involved in direct active trasport?
they have 8-10 transmembrane segments in a single polypeptide, which crosses the membrane multiple times
Where are the P-Type ATPases located that are involved in direct active transport?
most P-type pumps are located in the plasma membrane where they are responsible for maintaining an ion gradient across the membrane (example Na+/k+ pump)
What do the V-type ATPases do in direct active transport?
pump protons in to such organelles as vacuoles, vesicles, lysosomes, endosomes, and the golgi complex
Structure of V-type ATPases used in direct active transport?
- have two multisubunit components
1. an integral component embedded within the membrane
2. a peripheral component that juts out from the membrane surface - contains ATP binding site
Where are the F-Type ATPases used in direct active transport located?
Found in bacteria, mitochondria, choloroplasts
What are F-type ATPases involved in and what is the structure?
involved in proton transport and have two multisubunit components
- integral membrane component, called Fo, which is a transmembrane pore for proteins
- peripheral membrane component, called F1, which includes the ATP binding site
How do F-Type ATPases work in direct active transport?
They can use the energy of ATP hydrolysis to pump protons against their electrochemical gradient
How can F-type ATPases facilitate the reverse process of what they do in direct active transport?
ATP is synthesized, driven by the exergonic flow of proteins down their gradients: ATP synthases
ATP can be used as an energy source to generate ion gradients: can be used as an energy source to synthesize ATP
What does the “cassette” part in ABC (ATP binding cassette) transporters mean? (direct active transport)
the cassette describes the catalytic domain of the protein that binds ATP as an integral part of the transport process
What is the ABC transporter involved in?
- Importers involved in the uptake of nutrients
- exporters pump antibiotics or drugs out of the cell; drug resistance
ABC transporters have how many domains? (direct active transport) where are they?
-four domains: on separate polypeptides in most cases
two are highly hydrophobic and are embedded in the membrane
other two are peripheral and are associated with the cytoplasmic side of the membrane
