Question

Researchers studied the relationship between glucose concentration, oxygen level, and ATP production in one type of mammalian cell. Cells were isolated and cultured in growth medium containing either 1.5mM glucose or 25 mM glucose and at oxygen levels that varied from 0% to 21% . The researchers determined the concentration of ATP per cell under the different conditions. The ATP concentrations are shown as relative to the maximum ATP concentration obtained when cells were cultured in the presence of 25 mM glucose and 21% oxygen, standard culture conditions. The data are shown in Table 1.

Answer 1

Complete Question:

(a)  Describe the role of oxygen in cellular respiration.

(b) Using the template,  construct an appropriately labeled graph to represent the data in Table 1.

(c)  Describe the relationship between the concentration of glucose in the culture medium and the  ATP concentration in the cells.

(d) In a further experiment, the researchers add a compound to the cell growth medium that both binds and releases protons  (H+) and also passes through lipid membranes.  Predict the effect of this added compound on  ATP production by the cells.  Justify your prediction.

Answer and Explanation:

(a)  Describe the role of oxygen in cellular respiration.

Oxygen is essential for aerobic respiration only. This process occurs in the mitochondria and is abbreviated as :

C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + ≈38  

...this requires glucose, which is then broken down through several processes that begin in the cytoplasm, to produce energy in the form of ATP. To terminate the reaction, oxygen acts as the final electron acceptor after the electrons have traveled along the electron transport chain and ATPase. This forms water as a byproduct.

(b) Using the template,  construct an appropriately labeled graph to represent the data in Table 1.

An appropriate graph or data plot should be  a line graph. In the graph, (as seen in the attached example)

• the responding variable relative concentration of ATP should be placed on the y axis,
• the independent variable, the O2 concentration should be placed on the x axis.

Each varying concentration of glucose, should be plotted on a separate line within the graph, denoted in the legend.

(c)  Describe the relationship between the concentration of glucose in the culture medium and the  ATP concentration in the cells.

Glucose fuels the respiration process, and is broken down over a series of steps in glycolysis, the Kreb's cycle, and oxidative phosphorylation. With higher concentrations of glucose in the culture media, the rate of aerobic respiration increases as more glucose is processed. However, the breakdown of glucose shows higher efficiency (Table 1)  in  the presence of higher concentration of Oxygen.

(d)In a further experiment, the researchers add a compound to the cell growth medium that both binds and releases protons  (H+) and also passes through lipid membranes.  Predict the effect of this added compound on  ATP production by the cells.  Justify your prediction.

An electron transport chain, in Oxidative phosphorylation includes NADH and FADH2 which donate electrons and are converted to NAD+ and FAD. The donated electrons move down a chain of membrane proteins and release energy, the energy pumps protons out of the mitochondrial matrix.

The protons H+ build up and form a gradient in the intermembrane space of the mitochondria; they flow back into the matrix through ATP synthase in a process that leads to the production of ATP through the phosphorylation of ADP.

This cannot occur without the proton motive force formed through the buildup of H+ and the resulting chemiosmosis- here the H+ are not funneled through ATPase, disrupting the electron transport chain and reducing the amount of energy produced.