Glucose does not readily penetrate cell membranes as cell membranes are composed of phospholipids and glucose is hydrophilic and lipophobic due to the hydroxyl groups (Klein, 2013). Insulin, the major hormone that controls plasma glucose concentrations, increases the permeability of the liver, muscle and adipose or fat cell membranes to glucose (West & Passey, 1967). This allows for an increased rate of glucose transport from the plasma in the blood, across the cell membrane and uptake into these cells (Dimitriadis, Mitrou, Lambadiari, Maratou, & …show more content…
In this experiment, the administration of insulin caused plasma glucose concentration in the sheep to fall so low that homeostasis was disrupted and a stress response was triggered. In the experimental results, the maximum recorded serum cortisol concentration was 20 minutes after the minimum recorded plasma glucose concentration which occurred 40 minutes after insulin administration. This indicates that the cortisol response is rapidly triggered due to the low plasma glucose concentration whereas the effect of insulin on lowering the plasma glucose concentration is slower. Therefore, cortisol has an antagonistic effect on the stimulatory effects of insulin on the utilisation of glucose in adipose tissue in sheep (Plested, Taylor, Brindley, & Vernon, 1987) which supports the hypothesis of the experiment. The cortisol regulated the level of plasma glucose concentration and is essential when the concentration has been lowered by the insulin. The heightened serum cortisol concentration ensures a steady supply of glucose via activating the enzymes that are essential in gluconeogenesis (Randall,