Part a - the glucose-sodium cotransporter

the glucose-sodium cotransporter in animals, Na+ moves back into the cell down its electrochemical gradient, providing the energy for glucose to move into the cell against its concentration gradient.  
It makes sense css  glucose is cotransported with Na+ ions
In cotransport, the energy required to move one solute against its concentration or electrochemical gradient is provided by an ion moving into the cell down its electrochemical gradient. 

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature

Ithink b hope that