Membrane Transport II (Lecture 10) Flashcards
True or False: GLUT receptors undergo conformational changes while aquaporins do not.
True
Protein-mediated transport is faster than simple diffusion, highly specific, and the transport rate is limited by the number of transporters (____) and transporter affinity (____) for the molecule/ion
Vmax, Km
True or False: In ATP powered pumps, One or more bindings sites for ATP located on regions facing the inner lumen.
False, facing the cytosol
What are the four classes of ATP-powered pumps
P-class V-class F-class ABC superfamily
______ and ______ class pumps mostly transport H+ only, no phosphoprotein intermediate
V and F
______ pumps transport a wide array of substrates, including toxins, drugs, phospholipids, peptides, and proteins, into or out of the cell
ABC superfsmily
______ pumps are found in vacuolar membranes in plants, yeast and other fungi.
V-class
______ pumps are found in the inner mitochondrial membrane, bacterial plasma membrane and thylakoid membrane.
F-class
______ pumps transfer amino acids, sugars and peptides.
ABC superfamily
P-class pumps have ______ α subunits and ______ β subunits.
2,2
True or False: P-class pumps are often involved with generating ion gradients across membranes (ie. Na+, K+, Ca2+)
True
______ generally function to generate the low pH of plant vacuoles and of lysosomes and other acidic vesicles in animal cells by pumping protons from the cytosolic to the exoplasmic face of the membrane against a proton electrochemical gradient.
V-class pumps
______ are reverse proton pumps, also called ATP synthases
F-class
What does ABC stand for in pumps?
ATP-binding cassette
ABC pumps have two transmembrane ______ domains; form passageway
for cargo to pass through the membrane and Two cytosolic ATP-binding ______ domains; bind and hydrolyze ATP
T, A
True or False: Up to 50% of ATP produced by red blood cells is used for ion transport!
True
What pump is the most expensive?
Na/K
True or False: Ions spontaneously move through channels in the plasma membrane down their electrochemical gradients
True
In skeletal muscle cells, Ca2+ ions are concentrated and stored in the ______.
Sarcoplasmic reticulum
Ca2+ from the SR lumen into to the cytosol causes?
Muscle contraction
______ pumps in the SR membrane pumps Ca2+ from the cytosol back into the lumen of the SR, thereby inducing muscle ______.
P-class, relaxation
______ is a high-affinity Ca2+ binding protein bind large amounts of Ca2+, thus reducing the ‘free’ concentration
Calsequestrin
______ Makes up more than 80% of integral membrane
protein in muscle SR membranes
P-class Ca2+ ATPase
In the P-class Ca2+ ATPase, E1 states have the binding sites facing the \_\_\_\_\_\_ and E2 states have the binding sites facing the \_\_\_\_\_\_.
cytosol, exoplasmic face
Phosphorylation of ______ causes a E1 to E2 conformational change in P-class Ca2+ ATPase.
Aspartate
______ state has a high affinity for Ca2+ and ______ state has a low affinity for Ca2+.
E1, E2
E1 high affinity state: ______ oxygen atoms surround Ca2+ ions in two high affinity sites between helices ______, ______, ______, and ______ inside the membrane.
7
4, 5, 6, 8
P-class Na+/K+ ATPase moves ______ Na+ ions ______ of and ______ K+ ions ______ the cell per ATP molecule hydrolyzed
3 out, 2 into
If Km < free concentration (in the cytoplasm or external environment, depending on
direction pump is facing), then ions will ______.
Bind
All V-class only transport H+ ions to?
Acidify the
lumen of particular organelles
WHat are the two ways V-Class H+ ATPases can address positive charge build up?
Let in an equal number of anions to balance the charge
Move an equal number of a different cation out of the
organelle lumen
In ABC proteins, each transmembrane T domain has ______ membrane spanning alpha helices.
10
In ABC proteins, the two cytosolic ATP (A) binding domains are involved in?
Binding and hydrolysis drive change in conformation of the T domains
______ flips phosphatidylcholine from cytosolic to exoplasmic leaflet
ABCB4
True or False: Greater fluorescence (less quenching) in the presence of ATP than in its absence – indicates ABCB4 has flipped some of the labeled phospholipid to the inside leaflet
True
______ in the exocrine tissue transports Cl ions and cystic fibrosis occurs when protein is defective.
CFTR
Is CFTR a pump? why or why not?
Its not, its a Cl channel but uses T and A domains, and uses ATP.
True or False in ABC CFTR, channel opening is triggered by protein phosphorylation and by binding of ATP to the two A domains
True
