Mary wants to protect virgin forests from destruction. She climbs a tree to prev

Question

Mary wants to protect virgin forests from destruction. She climbs a tree to prevent loggers from cutting the oldest tree in the forest. Mary did not eat for twelve hours until a friend, Brian, took over the vigilance. Match the correct levels of blood glucose concentration, blood insulin concentration and relative membrane insulin receptor concentration for a skeletal muscle cell 20 hours into Brian’s fast and one hour after Mary had eaten a peanut butter and banana sandwich and a bowl of sweet potato soup. Provide a short explanation for your choices.

Plasma Glucose: 90 mg/dl; 125 mg/dl

Plasma Insulin: 10iuU/ml (70 pmol/L); 40iuU/ml (280 pmol/L)

Relative membrane insulin receptor concentration: increasing (high); decreasing (low)

Fasting (Brian)

Relative Membrane

Insulin Receptor Levels

Fasting (Brian)

Satiety (Mary) Plasma Glucose Plasma Insulin

Relative Membrane

Insulin Receptor Levels

Explanation / Answer

Relative Membrane Insulin

Receptor levels

Connecting 3 scenarios, usually whenever a person eats a meal, blood (plasma) glucose levels rise. This in turn stimulates production of insulin which is responsible for increasing gluocose uptake by tissues (skeletal muscles too). Increase in insulin levels in turn increase insulin receptor levels at the membrane of the cell in order to transport glucose into the cells.

Fasting (Brian) Explanation Satiety (Mary) Explanation Plasma Glucose 90 mg/dl Starvation reduces plasma gluocose levels but on prolonged starvation (more than 8 hours), glycogen is broken down to produce gluocose by muscle cells. 125 mg/dl Immediately after eating (Mary), plasma gluocose levels begin to rise and are usually less than 140 mg/dl for a non-diabetic person. Plasma Insulin 70 pmol/L Insulin levels are low due to low plasma glucose levels 280 pmol/L Insulin production is induced in reponse to elevated glucose levels in the plasma (homeostasis). This increases uptake of glucose into the cells.

Relative Membrane Insulin

Receptor levels

decreasing (low) As insulin levels are low due to low glucose levels in plasma, membrane receptor levels are also low. increasing (high) Insulin receptors levels at membrane increase due to increased insulin levels in muscle cells due to which we observe higher levels compared to fasting (in Brian)

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