Give a brief description of one positive feedback cycle ?

Outline how gut endothelial cells transport glucose from the gut lumen to the blood. Include all relevant transport mechanisms and the concentration gradients involved (is glucose going up or down its concentration gradient?
What was Gorter and Grendel’s contribution to our understanding of membrane structure? Outline their experiment that led to their model of membrane
What is the difference between a cofactor and a coenzyme? How are they similar?
Myoglobin (pictured below) is globular, oxygen-binding protein found in muscle and was the first protein whose structure was determined by x-ray crystallography. What level of protein organization does it represent? Label the levels of protein organization that can be seen in its structure.
Give a brief description of one positive feedback cycle ?