THE CHINGCHOK Hunter
Two amazing chemical reactions that form the circle of life
DAVID CANACAN
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| The elephant eats the grass as food for energy. The grass uses carbon dioxide breathed out by the elephant and nutrients produced in the elephant’s dung to produce oxygen, which is breathed in by the elephant. A brilliant combination! AMANDA SIM |
Every second an important chemical reaction takes place within the cells of all living things. One such reaction is respiration, which is the process by which all living things get energy.
During daylight, another chemical reaction, called photosynthesis, takes place in plants, certain bacteria and protists, such as algae, phytoplankton and seaweed. Every living organism, either directly or indirectly, relies on photosynthesis to respire (breathe).
Respiration
Respiration occurs in two ways. Aerobic respiration uses oxygen. Anaerobic respiration uses no oxygen. All higher organisms carry out both forms of respiration, and both are equally important to an organism's survival.
When you are not excited or under a threat, you respire calmly and aerobically. As you breathe in oxygen, it dissolves into your bloodstream through a process called diffusion.
Your red blood cells then transport the oxygen to all of the cells in your body where - along with glucose from your food absorbed into the bloodstream in your small intestine - the oxygen travels to special organelle structures in your cells called mitochondria.
Here, the oxygen and glucose react chemically and produce carbon dioxide, water and energy in the form of a molecule called adenosine triphosphate (ATP). With one glucose molecule reacting with six oxygen molecules, you can make 36 units of ATP, which is the energy currency for the cell.
But if a lion makes a dash for you, you'll need to react quickly, and this is where anaerobic respiration kicks in. The glucose breaks down without oxygen and forms lactic acid and two lots of ATP. This can give you a quick surge of energy in an emergency.
Oxygen debt
When you undergo heavy physical exercise, your lungs cannot supply your muscles with enough oxygen. You therefore undergo anaerobic respiration, which results in a build-up of lactic acid, which is toxic to the muscles. In order to stop this build-up, you need to begin respiring aerobically.
This is where you produce an oxygen debt, and immediately begin to pant after hard exercise to pay off the debt. One-hundred-metre sprinters complete the distance using anaerobic respiration, but they have to repay the debt as soon as possible.
This is why we can cover short distances in shorter average times than long distances, because you need to respire aerobically over long distances or the lactic acid build-up would be too much.
To experience anaerobic respiration and how it affects your muscles, try this little experiment. Place one of your arms straight above your head and then, as quickly as you can, open and close your fist repeatedly. You will soon feel the "burn" in your forearm, and you will no longer be able to continue opening and closing your fist at such a rapid rate.
Practical uses of anaerobic respiration
Unlike animals, when plants and fungi respire anaerobically, it is known as fermentation, and glucose, instead of being broken down into lactic acid, is broken down into carbon dioxide and ethanol.
Yeast, a fungus, is famous for its uses due to its ability to respire in the absence of oxygen. Like plants, it also produces carbon dioxide and ethanol, and this ability can be put to good use. Yeast is used to make bread - the bubbles you see are a result of the carbon dioxide produced during respiration, and they make the bread rise.
The ethanol produced also has a use, as ethanol is the same as alcohol (ethyl alcohol: C2H5OH). Therefore, yeast is used in the production of beer because of its ability to produce ethanol. Don't you just love respiration?
Photosynthesis
The reverse of respiration is photosynthesis. Whereas respiration uses glucose and oxygen to produce carbon dioxide and water, photosynthesis uses carbon dioxide and water to produce glucose and oxygen.
A photosynthetic organism's ability to utilise relatively simple molecules to make complex organic molecules such as glucose is why they make up the foundation of all food chains. Most of what we eat comes initially from plants. Poultry and meats are no exceptions, as chickens and cows eat mostly plants.
Plants produce organic compounds from inorganic molecules and water by utilising the energy from the sun. Some cells in leaves contain chloroplasts. Chloroplasts contain a chemical called chlorophyll, which absorbs red and blue light energy and transforms this energy into the chemical energy that drives photosynthesis.
Chlorophyll is the reason plants are green. Plants use red and blue light, but they cannot use green light. So, the green light is reflected and is not absorbed by the leaves.
Deforestation
Oxygen produced by plants keeps the oxygen levels in the atmosphere stable. Plants also take in carbon dioxide, a gas we are producing in excess. The excess carbon dioxide contributes to global warming.
Trees are felled at an unprecedented rate. Deforestation will be detrimental to our atmosphere and all life on Earth. Trees also provide complex habitats, which is why rainforests are so biologically diverse.
The interdependence of animals and plants - whereby each party produces materials for the other party's survival - creates a balance in nature and promotes the circle of life. The symbiotic relationship must be appreciated and protected.
The Plant A Tree Today project (http://www.plant-a-tree-today.org) realises the significance of trees to the reduction of global warming. It works extensively in Thailand, planting trees and helping the environment.
The next time you take a deep breath of fresh clean air, give thanks to a tree, and give something back.
Dave Canavan has an MSc in Behavioural Ecology and is the Head of Secondary at Garden International School. Dave is fascinated by science and loves animals, especially the dangerous kind! You may contact Dave at davidc@gardenbangkok.com .
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