Respiration (cont'd)
Monacia Williams, Contributor

How are you today? It seems like such a long time since we last communicated with each other. Was it just last week?

In these crazy pre-exam days, time seems to be doing some weird things to us. Don't worry too much though, we will survive!

Last week, we looked at aerobic respiration, which is respiration with oxygen, a process in which glucose is converted to carbon dioxide, water and energy. This week we will continue our study of respiration, but we will be looking at respiration without oxygen. This form of respiration is known as anaerobic respiration. And guess what? It also occurs in both plants and animals! There are, however, some differences in both. It is important for you to know these differences as well as the differences between aerobic and anaerobic respiration.

Let us now take a look at anaerobic respiration in plants. Anaerobic respiration in plants is also known as fermentation. Have you ever heard that word before? I bet you have, especially if you are doing food and nutrition or if you are a member of the 4H Club. This word is associated with alcohol, that's right, wines and rum! In fermentation, glucose is converted to alcohol, carbon dioxide and energy.

Glucose = alcohol + carbon dioxide + energy

The amount of energy produced is much less than that which is produced in aerobic respiration because some of it still remains trapped in the alcohol. If you were to react the alcohol with oxygen, it would release energy.

In one of the laboratory exercises that you will be required to carry out, the organism that is used to carry out fermentation is yeast. Yeast is used in wine-making, also in bread-making. It is easy to see the direct connection in wine-making, after all alcohol is produced but, how can it be used in baking you may ask? Remember the end products of fermentation? Alcohol, carbon dioxide and energy; carbon dioxide is a gas and as the yeast respires, carbon dioxide is produced and it is this gas which will cause the dough to rise. Again there is another but; but alcohol is produced you should be exclaiming now! What happens to it? The answer is that the high temperatures that are used in baking will cause all the alcohol to evaporate so there will be no taste of it in the finished product.

In animals, the products of anaerobic respiration are lactic acid and energy.

Glucose = lactic acid + energy

Humans carry out anaerobic respiration during periods of sustained physical activity. The activity causes the muscles to become fatigued and to stop contracting efficiently. The lungs and the heart cannot get oxygen to the muscles fast enough so that aerobic respiration can be carried out fast enough to provide the energy needed. This causes the muscles to carry out anaerobic respiration. As the glucose is broken down anaerobically, lactic acid builds up in the muscles. The build-up of lactic acid can poison the muscles and cause cramps. Our bodies must get rid of the lactic acid. How do we this? We do it by continuing to breathe faster and deeper even after we have finished the activity. The extra oxygen that we take in is used to convert the lactic acid to carbon dioxide and water. The oxygen that is used in the conversion is known as the oxygen debt. Sprinters tend to build up a lot of lactic acid during a 100 metre race because many of them tend to hold their breaths while running. This translates to very little aerobic respiration taking place . In order to repay the oxygen debt created, they need to breathe very deeply to provide the seven litres of oxygen which will be required to repay this debt.

I hope that you will take the time to make sure that you thoroughly understand this topic. It is a very important one that is tested fairly often in the examinations.

Next week, we will take a look at some of the experiments that should be carried out while you are doing the topic. In many instances, the questions are based on the experiments! Have a wonderful week!

Sheer poetry in motion. - Ricardo Makyn/Staff Photographer.