State the functions of the following organelles of a eukaryotic animal cell: lysosome, Golgi apparatus, free ribosomes, plasma membrane, rough endoplasmic reticulum.

Distinguish between anaerobic and aerobic cell respiration in eukaryotes.

Explain the mechanism of ventilation in the lungs in order to promote gas exchange for cell respiration.

lysosome:
a. (from Golgi apparatus) with digestive enzymes / break down food/organelles/ cell;

Golgi apparatus:
b. site that processes/modifies/packages and releases proteins;

free ribosomes:
c. site of synthesis of proteins (released to cytoplasm);

plasma membrane:
d. controls entry and exit of materials/substances in cell;

rough endoplasmic reticulum:
e. synthesis and transport of proteins; (both needed)

Award [1] for each contrasting characteristic.   

Table format is not necessary for the marks.

a. inspiration/inhalation brings air into lungs;
b. external intercostal muscles contract;
c. and move rib cage upwards and outwards;
d. diaphragm flattens/contracts;
e. increasing thoracic volume;
f. pressure decreases from atmospheric pressure so air rushes into lungs;
g. expiration/exhalation forces air out;
h. internal intercostal muscles contract / external intercostal muscles and diaphragm relax;
i. abdominal/abdomen wall muscles contract and push diaphragm upwards;
j. decreasing thoracic volume;
k. increasing pressure in lungs so air is forced out;
l. a concentration gradient between air sacs and blood needs to be maintained;

Question 6 was the most popular to answer.

The major confusions were found when explaining the functions of the Golgi Apparatus and the rough endoplasmic reticulum. Some candidates did not make any reference to proteins when explaining the function of the Golgi, for which they did not receive the mark.

Marks were not awarded generally for incomplete answers. E.g. Not mentioning one of the end products of anaerobic respiration, either CO₂ or ethanol or in products of aerobic respiration, water was often omitted. The comparisons were sometimes difficult to spot, given that they did not use a chart or did not follow a proper order. Finally some candidates simply failed to compare, explaining only one type of cell respiration.

There were quite a few students who gave very good descriptions of gas exchange and even respiration in some cases, and the properties of the alveoli that made them well adapted for gas exchange. Unfortunately the question was "Explain the mechanism of ventilation in the lungs in order to promote gas exchange for cell respiration". Many candidates did not read the question correctly. Some candidates even gave more detail of aerobic respiration here than they did in part b. Among the most common errors found were to say that "...inspiration brings oxygen into the lungs" and that "...expiration releases CO₂". In some of the answers there was no differentiation between external and internal intercostal muscles. Some candidates referred to changes in the lung volume, instead of thoracic volume.