Mitochondria convert the energy from the food that we eat into a chemical energy that we can use in the form of ATP. Adenosine triphosphate (ATP) is a chemical compound which serves as the chemical fuel of living organisms. ATP is composed of adenine, ribose, and 3 phosphate groups.

C. ATP

The first step in releasing the energy in glucose is glycosis. Glycolysis occurs when glucose is broken down into half to produce energy. The end products of this process include 2 pyruvic acid molecules, 2 NADH molecules, and a net gain of 2 ATP molecules.

B. glycolysis

Cellular respiration is the metabolic reaction that takes place when an energy is released by the breakdown of molecules, such as glucose, in the presence of oxygen.

B. cellular respiration

Cellular respiration is the release of energy from food with the help of oxygen.

All organisms must get energy from the chemical energy of food, regardless of whether they created the food themselves or took it from the environment, hence all perform cellular respiration.

D

During glycolysis, there are 2 ATP molecules, 2 pyruvic acid molecules, and 2 NADH molecules that are produced.

B. 2 ATP molecules

When oxygen is not present, glycolysis is usually followed by fermentation; hence, fermentation is anaerobic. Anaerobic is a term that is used to describe a process or an activity which do not require oxygen.

B. anaerobic

C. mitochondrion

The high-energy electrons from glycolysis and Krebs cycle are utilized by the electron transport chain to convert ADP into ATP.

B. convert ADP to ATP

During glycolysis (anaerobic), there are 2 ATP molecules that are produced. On the other hand, during cellular respiration (aerobic), there are 36 ATP molecules that are produced.

A. cellular respiration

Heavy exercise results in the buildup of lactic acid since the supply of oxygen is not enough to keep up with the demands of the muscle cells. Hence, the cells need to switch to lactic acid fermentation to continue producing energy due to the lack of oxygen.

The accumulation of lactic acid in muscle cells results in a condition called **oxygen debt**. This corresponds to the amount of oxygen that is needed to remove the lactic acid and replenish the oxygen reserves in muscle cells when oxygen is adequately supplied again.

B

The term calorie is described as the amount of energy that is needed to raise the temperature of one gram of water by 1 degree Celsius. The calories we get from the food that we eat serve as a fuel to provide us with energy in the form of heat. Cells use high-calorie molecules such as glucose in a process called cellular respiration. During cellular respiration, oxygen is required. Once a glucose molecule is broken down, there are 36 ATP molecules that are produced.

Glycolysis occurs when glucose is broken down into half to produce energy. Since glucose has 6 carbons and pyruvic acid has 3 carbons, there are 2 pyruvic acids that are produced for each one glucose molecule in the process of glycolysis. The end products of this process include 2 pyruvic acid molecules, 2 NADH molecules, and a net gain of 2 ATP molecules.

Glycolysis is followed by two different pathways. The first pathway is called the Krebs cycle, which is the second stage of cellular respiration. In this process, oxygen is required for the final step of releasing the energy from the glucose. On the other hand, the second pathway leads to fermentation, which releases energy from the glucose molecules in the absence of oxygen.

Here is a sample diagram which show how glucose is broken down in the mitochondrion.

Cellular respiration and fermentation are both involved in the process of releasing chemical energy. However, they differ in terms of the reactants involved in the process.

In cellular respiration, the process starts with oxygen and glucose (6-carbon molecule) to produce ATP. Cellular respiration is aerobic since oxygen is required for releasing the energy from the glucose.

On the other hand, fermentation starts with pyruvic acid (3-carbon molecule) and NADH. The end products of fermentation can either be an alcohol and carbon dioxide, or lactic acid. This process releases energy from the glucose molecules in the absence of oxygen; hence, it is anaerobic.

ATP synthase, which is an enzyme found in the mitochondria, is responsible for converting adenosine diphosphate (ADP) into adenosine triphosphate (ATP) during cellular respiration. ATP is a chemical compound which serves as the chemical fuel of living organisms. It is the energy source of a cell in doing its metabolic activities. Without the ATP synthase, ATP molecules will never be formed.

We rely on ATP when our bodies need energy. To obtain the energy needed, the body uses the ATP produced from three sources – stored ATP, ATP from lactic acid fermentation and cellular respiration. Stored ATP and ATP from lactic acid fermentation can only supply energy for 90 seconds. Therefore, in order for a runner to withstand a 20-minute race, he will use the ATP from cellular respiration. Cellular respiration can store energy that can last for 15 to 20 minutes. After this, the body will start to break down other molecules like fats in order to produce energy.

1. Carbon dioxide and water
Photosynthesis uses light energy by converting carbon dioxide and water into glucose and oxygen. This process takes place in the chloroplast.

2. Cellular respiration
In cellular respiration, the process starts with oxygen and glucose (6-carbon molecule) to produce ATP. This process takes place in the mitochondria.

1 – Carbon dioxide and water
2 – Cellular respiration

All eukaryotes possess mitochondria, which is known as the site of the electron transport chain during cellular respiration. In photosynthetic organisms, such as plants and algae, electron transport chain happens in the thylakoid membrane of chloroplasts. On the other hand, prokaryotes lack mitochondria. Since they do not possess membrane-bound organelles, they perform the electron transport chain in their cell membranes.

Since there are habitats that lack oxygen, some organisms rely on breaking down fuels in the absence of oxygen. Bacteria and archaea such as methanogens living in the soil, release energy using anaerobic respiration. Anaerobic is the term that describes a process or an activity that does not require oxygen.

Mitochondria is the center for ATP (energy) production. Therefore, if you have more mitochondria in muscle cells, you would increase the ATP production giving your cells the ability to generate energy to be consumed in energy-consuming activities more easily.

In cellular respiration, 38 ATP molecules are produced per glucose, whereas 2 ATP molecules are produced in fermentation. In this case, fermentation is considered as less efficient when using the energy from glucose. In order for the yeast cells to grow more rapidly, they must carry out cellular respiration.

After using all the ATP supply, the body will start to need more oxygen for cellular respiration. If the body could not get enough oxygen, anaerobic respiration will occur and there would be a lactic acid build up in the body. The lactic acid build up causes the muscles to feel tired or painful. In this case, if the muscles are pumped up with blood that contains sufficient oxygen, cellular respiration (aerobic) will be maintained and it will avoid lactic acid build up. The reason why people must do aerobic exercises because this kind of exercise will help strengthen the heart and lungs to utilize the oxygen supply properly.

To test, ask two persons to participate in this experiment. The first person (person A) must be asked to do a jogging exercise for ten days straight, while the second person (person B) must refrain from doing any exercises for ten days straight. On the eleventh day, ask them to ride a bicycle. They must keep cycling for thirty minutes with no rest. Once done, ask them if they feel any muscle discomfort, nausea, or weakness. If person B experiences muscle discomfort that is more painful that what person A felt, this means that there is more lactic build up in person B than person A.

In the given scenario, it was observed that a small amount of lactic acid is present after a heart attack. Lactic acid is produced through fermentation, which occurs under anaerobic conditions.

The presence of lactic acid in the heart muscle cells suggests that the cells have undergone fermentation. This implies that the cells had been under anaerobic (oxygen-free) conditions.

Therefore, we would conclude that the nature of a heart attack is due to the absence of oxygen. This explains why the heart muscle cells had produced lactic acid after a heart attack.

Carbon monoxide competes and replaces oxygen in the bloodstream. Because of this, blood cells bind to carbon monoxide instead of oxygen. This causes the level of carbon monoxide in the body to increase and the level of oxygen in the body to decrease. As a result, the organism is deprived of oxygen and eventually dies.