Question

feedback loop analysis activity

purpose: whether or not a process is controlled by negative or positive feedback loops can often be determined by examining graphs of relevant data. in this exercise, you will make graphs using various sets of data. you can then use the graphs to determine whether a positive or negative feedback loop is at work.

feedback scenario #1: after a meal, the concentration of glucose in a person’s blood will start to change from its baseline value, as shown in data table 1.

table 1: glucose levels in the blood after eating

time after eating (min)	blood glucose concentration (ng/ml)
15	130
30	175
45	162
60	150
75	145
90	140
120	119
150	100
180	80

1. use table 1 to find the correct statement below. table 1 shows blood glucose levels over time after eating. which statement best describes the trend that would appear if this data were graphed?

a) blood glucose rises slowly after eating, peaks near 30 minutes, and continues increasing until 180 minutes have passed.
b) blood glucose stays about the same from the time of eating until 180 minutes have passed.
c) blood glucose rises quickly after eating, peaks near 30 minutes, then gradually returns to the starting level by 180 minutes.
d) blood glucose drops steadily from the start, reaching its lowest level at 180 minutes after eating.

Explanation:

• Analyze each option by checking the data in Table 1:
• Option a: The glucose level starts at 80, rises to 175 at 30 min, then decreases (e.g., 162 at 45, 150 at 60, etc.), so it does not continue increasing until 180 min. Eliminate a.
• Option b: The glucose level changes significantly (from 80 to 175 and back to 80), so it does not stay about the same. Eliminate b.
• Option c: At 0 min, glucose is 80. It rises to 175 at 30 min (quick rise initially), then decreases: 162 (45), 150 (60), 145 (75), 140 (90), 119 (120), 100 (150), and back to 80 at 180 min. This matches the description of rising quickly, peaking near 30 min, then returning to the starting level.
• Option d: The glucose level increases first (from 80 to 175), so it does not drop steadily from the start. Eliminate d.

Answer:

c) Blood glucose rises quickly after eating, peaks near 30 minutes, then gradually returns to the starting level by 180 minutes.