Question

The carrier proteins through which sugar enters pancreatic beta cells have _______________ (A Lower Km or A Higher Km or The Same Km) than the carriers through which sugar enters muscle cells at fasting blood sugar levels. In order for muscle cells to increase sugar import ______________ (Blood sugar levels must be high or Insulin must be present or Glycogen must be presentor gen Glucagon must be present). Oh, and glucokinase has a _______________ (High Km or Low Km ) when compared to hexokinase.

_______________ (Proton Pumps or Iron Reductases or Ferriportins orIron Oxidases) are responsible for the release of transferrin from the transferrin receptor and iron form transferrin. _______________ (Proton Pumps or Iron Reductasesor Ferriportins or Iron Oxidases) Convert the iron to the active form in which it may be exported. This happens in the ________________ (Lysosome orCytoplasm or Intermembrane Spaceor Interstitial Fluid ).

Answer 1

The carrier proteins through which sugar enters pancreatic beta cells have Higher Km (A Lower Km or A Higher Km or The Same Km) than the carriers through which sugar enters muscle cells at fasting blood sugar levels.

• Explanation: A high Km value indicates low affinity for the substrate. The carrier protein (GLUT4) which is present on the muscle cells has a higher affinity for glucose (low Km 1.8-4.8mM) thereby ensuring maximum glucose transport in tissues when glucose concentration falls. On the other hand the carrier proteins found on beta cells (GLUT2) have a high Km ~20mM, as a higher Km allows for glucose sensing.

In order for muscle cells to increase sugar import Insulin must be present (Blood sugar levels must be high or Insulin must be present or Glycogen must be present or gen Glucagon must be present). Oh, and glucokinase has a High Km (High Km or Low Km ) when compared to hexokinase.

• Explanation: Glucokinase has a lower affinity (higher Km) for glucose as it only operates under conditions of high glucose levels in serum.

Proton pumps (Proton Pumps or Iron Reductases or Ferriportins or Iron Oxidases) are responsible for the release of transferrin from the transferrin receptor and iron form transferrin.

• Explanation: H+ ATPases decrease the pH of the vesicle and causes transferrin to release iron.

Iron Reductases (Proton Pumps or Iron Reductases or Ferriportins or Iron Oxidases) Convert the iron to the active form in which it may be exported. This happens in the Lysosome (Lysosome or Cytoplasm or Intermembrane Space or Interstitial Fluid ).

• Explanation: Ferric iron is converted to ferrous iron (active form) by the action of ferric reductase