biology - chapter 5: Respiration - exam questions

Describe the process of glycolysis

Malonate inhibits a reaction in the Krebs cycle. Explain why malonate would decrease the uptake of oxygen in a respiring cell

In muscles, pyruvate is converted to lactate during prolonged exercise. Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration.

Yeast cells can respire aerobically or anaerobically. A student used the apparatus shown in Figure 1 to measure the rate of respiration in yeast. She:

• positioned the flask in a water bath so that the yeast culture reached a constant temperature

• then left the apparatus for one hour before starting her investigation.

(a) Suggest one reason why it was important that the student left the apparatus for one hour after the yeast culture reached a constant temperature.

Yeast cells can respire aerobically or anaerobically. A student used the apparatus shown in Figure 1 to measure the rate of respiration in yeast. She:

• positioned the flask in a water bath so that the yeast culture reached a constant temperature

• then left the apparatus for one hour before starting her investigation.

(b) During her investigation, the coloured liquid moved to the right. Explain why it moved to the right.

During her investigation, the coloured liquid moved to the right. Explain why it moved to the right.

Explain why a log scale is used to record the number of cells

Many yeast cells die during the death phase. Suggest one reason why

The following equation can be used to make predictions of the growth in the population of yeast cells under ideal laboratory conditions. Xt = X0 ert

Xt = the population after a certain time

X0 = the population at the start

e = 2.72 (base of natural logarithm)

r = growth rate

t = time period in hours over which r applies A population of 2000 yeast cells was left for 10 hours. The value for the growth rate was 0.5

Assuming no yeast cells died, calculate the predicted size of the population after 10 hours. Show your working.

AMP-activated protein kinase (AMPK) is an enzyme that regulates a number of cellular processes. Exercise leads to activation of AMPK. The diagram shows one effect of activation of AMPK during exercise. CPT1 is a channel protein that transports fatty acids into mitochondria.

Using the diagram above, explain the benefit of activation of AMPK during exercise

The figure below shows the apparatus used for measuring the rate of oxygen consumption in aerobic respiration by seeds

For the first 10 minutes, the tap attached to tube A was left open and the syringe from tube B was removed. Suggest three reasons why the apparatus was left for 10 minutes.

The figure below shows the apparatus used for measuring the rate of oxygen consumption in aerobic respiration by seeds

Suggest and explain why the chosen temperature was 20 °C for this experiment.

After 10 minutes, the tap attached to tube A was closed and the syringe was attached to tube B. Every minute, the syringe plunger was moved until the levels in the U-tube were the same. The reading on the syringe volume scale was then recorded. The results are shown in the table below.

During the experiment, the coloured liquid in the tubing moved towards tube B. Explain what caused this.

The mass of the seeds was 1.6 g. Use the information in the table above to calculate the rate of oxygen consumption in cm3 g–1 hour–1 by the seeds. Show your working.