Homeostasis · Paper 2 — Free Biology SL Practice Questions

A research team investigates the effect of a new drug, GlucoStat, on blood glucose regulation in healthy laboratory rats. Rats are divided into a control group (injected with saline) and an experimental group (injected with GlucoStat). After 30 minutes, both groups receive an intravenous injection of glucose solution ($0.5\,\text{g kg}^{-1}$ body mass). Blood glucose concentration is measured every 15 minutes for 120 minutes. - Baseline blood glucose (both groups): $4.8\,\text{mmol L}^{-1}$ - Control group: peak at 15 min = $10.2\,\text{mmol L}^{-1}$; returns to baseline by 90 min - GlucoStat group: peak at 15 min = $9.1\,\text{mmol L}^{-1}$; returns to baseline by 60 min

A researcher investigates insulin action using cultured human skeletal muscle cells (myocytes). Cells are incubated in medium containing $20\,\text{mmol}\,\text{L}^{-1}$ glucose. One group is treated with $100\,\text{nM}$ insulin; a control group receives no insulin. After 30 minutes, GLUT4 glucose transporter proteins are counted. Group — GLUT4 on cell surface membrane — GLUT4 internal vesicles Control — 200 per cell — 4800 per cell Insulin-treated — 4800 per cell — 200 per cell Total GLUT4 per cell (surface + internal) = 5000 in both groups.

A clinical study investigated blood glucose regulation in two groups of healthy adults ($n = 15$ each) following an oral glucose tolerance test (OGTT). Participants fasted for 12 hours, then consumed $75\,\text{g}$ of glucose dissolved in water. Blood samples were taken every 30 minutes for 180 minutes. Mean blood glucose concentration ($\text{mmol}\,\text{L}^{-1}$): Time (min) — Group A (control) — Group B (soluble fibre) 0 — 4.8 — 4.7 30 — 8.2 — 6.9 60 — 7.5 — 6.1 90 — 6.0 — 5.2 120 — 5.1 — 4.9 180 — 4.9 — 4.8 Group B consumed $10\,\text{g}$ of soluble fibre 30 minutes before the glucose drink.