Question
Topic – 2.5 Membrane Transport
(a) – Topic – 2.8 Mechanisms of Transport
(b) –
(c) -Topic – 2.6 Facilitated Diffusion
(d) –
To investigate whether red blood cells of animals lose the ability to take in glucose from their environment as they age, scientists collected red blood cells from guinea pigs that ranged in age from one day old to seven
months old. Scientists incubated an equal number of red blood cells in separate culture dishes that contained a 300 nM solution of radioactively labeled glucose. The amount of radioactively labeled glucose present inside the red blood cells of each group was measured over time.
(a) Describe a difference between passive transport and active transport.
(b) Justify why the scientists used an equal number of red blood cells in each culture dish as a control.
(c) Glucose transporters are required for the facilitated diffusion of glucose into red blood cells. The scientists claim that the expression of the gene encoding these transporters decreases as guinea pigs age. If the
scientists’ claim is supported by experimental data, predict the effect of increased age on the amount of radioactively labeled glucose present inside the cells of each group.
(d) Justify your prediction in part (c).
▶️Answer/Explanation
3(a) Describe a difference between passive transport and active transport.
Accept one of the following:
• Active transport requires energy/ATP (while passive transport does not).
• Passive transport does not require energy/ATP (while active transport does).
• In passive transport, substances move from a high concentration to a low concentration, (while in active transport substances move from a low concentration to a high concentration).
• In active transport, substances move from a low concentration to a high concentration (while in passive transport substances move from a high concentration to a low concentration).
3(b) Justify why the scientists used an equal number of red blood cells in each culture dish as a control.
Accept one of the following:
• (Scientists used an equal number of cells) to attribute differences in results/glucose transport to guinea pig age, (rather than to the number of cells used in the experiment).
• (Scientists used an equal number of cells) to compare results from the different dishes (containing cells from guinea pigs of different ages).
• (Scientists used an equal number of cells) to eliminate the number of cells as a variable (that might affect the amount of glucose in each group).
• (Scientists used an equal number of cells) because the number of cells used might affect the results/amount of glucose (present inside the red blood cells).
3(c) Glucose transporters are required for the facilitated diffusion of glucose into red blood cells. The scientists claim that the expression of the gene encoding these transporters decreases as guinea pigs age. If the scientists’ claim is supported by experimental data, predict the effect of increased age on the amount of radioactively labeled glucose present inside the cells of each group.
• (As guinea pig age increases) the amount of glucose (inside the cells) decreases.
4(d) Justify your prediction in part (c).
• With fewer transporters, fewer glucose molecules will be moved into the cells.