ATP Powered Pump Flashcards
What are ATP-powered pumps?
ATP-powered pumps (or simply pumps) are ATPases that use the energy of ATP hydrolysis to move ions or small molecules across a membrane against a chemical concentration gradient or electric potential or both.
What is the process that involves moving ions or small molecules ‘uphill’ against an electrochemical gradient called?
Active transport
What are the three classes of ATP-powered transport proteins?
P-class ion pumps
V-class proton pumps
ABC superfamily
What do all P-class ion pumps possess?
Two identical catalytic α subunits that contain an ATP-binding site.
What is the significance of the phosphorylation in P-class ion pumps?
At least one of the α subunits is phosphorylated during the transport process.
What is the function of the Muscle Ca2+ ATPase?
Pumps Ca2+ ions from the cytosol into the sarcoplasmic reticulum.
What triggers muscle contraction in skeletal muscle cells?
Release of stored Ca2+ ions from the sarcoplasmic reticulum into the cytosol.
What are the two conformational states of the Ca2+ ATPase protein?
E1 and E2.
What occurs in Step 1 of the Ca2+ ATPase mechanism?
Two Ca2+ ions bind to high-affinity sites and ATP binds to the cytosolic surface.
What happens to ATP during the Ca2+ ATPase mechanism?
It is hydrolyzed to ADP and a phosphate is transferred to a specific aspartate residue.
What is the role of Mg2+ in the Ca2+ ATPase mechanism?
It is required for the hydrolysis of ATP.
What is the effect of the conformational change from E1 to E2 in the Ca2+ ATPase?
It generates lower-affinity Ca2+ binding sites accessible to the SR lumen.
What is the main function of the Na+/K+ ATPase?
Maintains intracellular Na+ and K+ concentrations in animal cells.
What is the composition of the Na+/K+ ATPase?
A tetramer of subunit composition ɑ2β2.
What happens in Step 1 of the Na+/K+ ATPase mechanism?
The enzyme has three high-affinity Na+ sites and two low-affinity K+ sites accessible from the cytosolic surface.
What is the outcome of the E2 conformational state in the Na+/K+ ATPase?
It exposes low-affinity Na+ sites and high-affinity K+ sites to the exoplasmic face.
What do V-class proton pumps primarily do?
Maintain low pH in plant vacuoles and lysosomes by pumping protons.
What type of ions do V-class ATPases transport
H + ions.
What is the effect of proton pumping by V-class pumps?
It generates an electric potential across the membrane.
What is the structural organization of ABC transport proteins?
Two transmembrane (T) domains
Two cytosolic ATP-binding (A) domains
What is the role of the MDR1 protein?
Exports a large variety of drugs from the cytosol to the extracellular medium.
What is the pH of the cytosol compared to that of lysosomes?
Cytosol pH is about 7.2, while lysosomes maintain an acidic pH of about 5.0.
What do ABC transport proteins typically transport?
Ions
Sugars
Amino acids
Phospholipids
Peptides
Polysaccharides
Proteins
Fill in the blank: ATP-powered pumps (or simply pumps) are ATPases that use the energy of _______ to move ions or small molecules across a membrane _______.
ATP hydrolysis; against a chemical concentration gradient or electric potential.
