1. In myosin a) there are two heavy chains and two light chains b) the heavy cha
ID: 41994 • Letter: 1
Question
1. In myosin
a) there are two heavy chains and two light chains
b) the heavy chains associate by forming a double-stranded coiled coil c) the actin binding sites are located on the light chains
d) the globular heads are the sites for interaction with tropomyosin
2. In muscle contraction
a) for each power stroke a single molecule of ATP is hydrolyzed by actin
b) calcium binding to troponin C allows the binding of tropomyosin to actin c) binding of ATP to myosin causes it to dissociate from actin
d) the power stroke occurs when ATP is hydrolyzed to ADP plus phosphate
3. Integral membrane proteins of the plasma membrane
a) freely flip over within the phospholipid bilayer
b) have oligosaccharides attached to the cytoplasmic portion of the polypeptide c) often contain multiple polypeptide chains
d) always have the N-terminus on the cytoplasmic side of the membrane
4. Which statement about Na+-K+ ATPase is NOT true?
a) Three Na+ ions bind to the protein on the cytoplasmic side of the membrane.
b) Na+ binding is followed by the phosphorylation of the hydroxyl group of a threonine residue. c) The phosphorylated protein binds K+ on the extracellular side of the membrane.
d) The action of the protein causes the inside of the cell to acquire a negative charge.
5. In the intestinal glucose transporter, the energy for glucose uptake comes from a) the simultaneous import of sodium ions
b) the simultaneous import of potassium ions
c) the collapse of an H+ gradient
d) an opening of the channel caused by Na+ binding
6. Which of these statements about the aldolase reaction is NOT true?
a) It is an example of electrophilic catalysis.
b) Fructose-1,6-bisphosphate binds covalently to the active site.
c) The first product released after cleavage is dihydroxyacetone-P.
d) A carbanion intermediate is stabilized by conjugation to a positively charged nitrogen.
7. The lactate dehydrogenase reaction
a) is the final reaction of glycolysis under aerobic conditions
b) is used to regenerate NAD+ from NADH when O2 is limiting c) catalyzes an essential step in the production of ethanol by yeast d) produces NAD+ which can be oxidized in the mitochondria
8. The reaction which involves a phosphohistidine intermediate is
a) phosphofructokinase
b) phosphoglucoisomerase
c) phosphoglyceromutase
d) enolase
9. The only type of compound listed below which is NOT a "high-energy phosphate" is
a) phosphate ester
b) acyl phosphate
c) enol phosphate
d) phosphoanhydride
Explanation / Answer
1) actin binding site are located on light chain
2) d is not correct. the bound ATP dissociates into ADP +Pi, and when Pi is released, a power stroke is generated.
3)
4)
5) from symport of Na+ ions
6)fructose 1,6-bis phosphate binds covalently to active site is incorrect.
7) a) it is the final step of glycolysis under anaerobic conitions
8) enolase
9)acyl phosphate
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