Respiration
Monacia Williams, Contributor

How are you today? All set to go? I hope you have been benefitting from the questions that we have been going through over the last couple of weeks. Last week, I told you that this week we would start a new topic, respiration.

There are a few misconceptions associated with this topic. Let us see if we can clear up some of them now. The first is the concept that most students have of the respiration; most tend to equate respiration with breathing and this is not so. Breathing is not a part of respiration it is the means by which the respiratory gas, oxygen, gets into the lungs. Think about it, if breathing were respiration, what would happen to aquatic animals? They do not breathe! The second misconception is the belief that respiration only occurs in animals. This is not so. Respiration occurs in both plants and animals.

What is respiration?

Respiration is the process by which the energy in food is made available to a cell to do the work necessary to keep it alive. The process occurs at the level of the cell and, hence, is called cellular or tissue respiration. Like all the other reactions which take place within the cell, the process requires enzymes. The organelle within the cell which is involved in respiration is the mitochondrion (please note that the plural form is mitochondria). Cells which are very active, for example, liver, muscle, root and stems tips, have large numbers of mitochondria.

What is involved in the process?

Do you remember the topic we just completed? Food, especially carbohydrate, is taken into the body and during digestion is converted to glucose. The glucose is absorbed in the small intestine and enters the blood stream from there. It is this glucose that is the food mentioned in the definition and it is known as the respiratory substrate. How is the energy released for it to be made available to the cell? This requires the use of oxygen, which is known as the respiratory gas.

Glucose is oxidised in stages, each stage releasing a certain amount of energy. The released energy is stored in a molecule called adenosine tri phosphate (ATP).

ATP is made from two molecules within the cell. These molecules are ADP (adenosine di phosphate) and Pi (high-energy phosphate molecule). It requires a lot of energy to join the phosphate group to ADP and this energy becomes trapped in the molecule. When glucose is oxidised, the energy released at each stage is used to join these two molecules. The energy stored in the ATP molecule can be released readily when the ATP is converted back to ADP and Pi. This system of storage conveys certain advantages to the organism.

These are as follows:

• The amount of energy wasted as heat is reduced.
• ATP can diffuse into and out of cells and can, therefore, go where it is needed.
• ATP breaks down rapidly so energy is readily available.
• This energy can be used to drive many reactions within the cell.
• Energy can be stored as ATP in one part of the cell and transported to be used in another part.

What are the other end products of respiration?

These are:

• Carbon dioxide
• Water

The process can be summarised in the following equation:

C₆H₁₂O₆ + 6O₂ = 6CO₂ + 6H₂O + energy

The energy that is produced in respiration is used to do the following:

• Mechanical work, for example, contraction of heart muscle, skeletal muscle and gut muscle.
• Chemical work in the liver, kidneys, nerve impulses.
• Growth and repair - cell division for growth of new tissues and the repair of old ones.
• Anabolism - making proteins (enzymes and hormones) carbohydrates.
• To provide heat - this heat is used to maintain body temperatures in warm- bloodied animals.

This type of respiration where oxygen is used to oxidise glucose is known as aerobic respiration.

Join me again next week when we will look at another type of respiration known as anaerobic respiration.

Kingston College students celebrate with members of the triumphant Television Jamaica's Schools' Challenge Quiz team, during a tour of the school's Melbourne campus, April 1. The team members, who are all based at the school's North Street campus, marched to the lower school yesterday. They beat Ardenne High School 42-14 during the finals on March 31. In blazers from left are Oral Lawson, Kenneth Peart, Roland Douglas and Alain N'Dalla. - Norman Grindley/Chief Photographer