Respiration

Respiration

Is the metabolic activity or reaction in which complex food substances are broken down step by step to release energy within a cell.

Cellular respiration

Is a set of metabolic reaction and process that takes place in the cell of organisms to convert biochemical energy from nutrients into ATP.

Types of respiration

1. Aerobic Respiration
2. Anaerobic Respiration

Aerobic respiration

Aerobic respiration is the process in which oxygen is used to break down glucose, producing energy, carbon dioxide, and water. The energy is released in the form of ATP (adenosine triphosphate), with a total of 38 ATP molecules produced per molecule of glucose.

This type of respiration occurs in two stages:

Glycolysis

This occurs in the cytoplasm and does not require oxygen, making it a common phase for both aerobic and anaerobic respiration. During glycolysis, glucose is broken down into pyruvic acid, producing 2 ATP molecules.

Kreb's Cycle (Citric Acid Cycle)

This occurs in the mitochondria, where pyruvic acid is further broken down in the presence of oxygen. During this cycle, citric acid (a six-carbon molecule) is formed, which leads to the production of ATP and other energy-rich molecules.

Anaerobic respiration

Anaerobic respiration occurs in the absence of oxygen and involves the breakdown of glucose without the use of oxygen. In plants, anaerobic respiration is also known as fermentation, which produces alcohol, carbon dioxide, and energy. The chemical equation for fermentation in plants is:

• Glucose → Ethanol + Carbon dioxide + Energy

In animals, anaerobic respiration results in the production of lactic acid and energy:

• Glucose → Lactic acid + Energy

During strenuous activity, anaerobic respiration occurs when the oxygen supply to muscles is insufficient. This causes the accumulation of lactic acid in the muscles, which can be toxic. To recover, the body needs to "repay" the oxygen debt by breathing deeply and quickly to convert lactic acid back into carbon dioxide and water. Some lactic acid can also be converted back into glucose.

Types of anaerobes

There are two types of anaerobes:

1. Obligate Anaerobes: These organisms can only survive and respire in the absence of oxygen and die when exposed to oxygen.
2. Facultative Anaerobes: These organisms can survive and respire both in the presence and absence of oxygen.

Differences between aerobic and anaerobic respiration

Aerobic Respiration	Anaerobic Respiration
Oxygen is used	Oxygen is not used
Large amounts of energy are produced	Small amounts of energy are produced
Water molecules are produced	Water is not produced
Food substances are completely broken down	Food substances are not completely broken down
Takes place in the mitochondria and cell membrane	Takes place in the cytoplasm
Carbon dioxide and water are the end-products	Lactic acid is produced in animals and alcohol is produced in plants

Factors affecting the rate of respiration

Temperature

Enzyme Function: Respiration is enzyme-controlled, and enzymes work best at an optimal temperature. At low temperatures, respiration slows down. As the temperature rises, the rate of respiration increases until it reaches the optimal temperature. Beyond this point, if the temperature is too high, enzymes become denatured, and the rate of respiration decreases.

Activity

Energy Demand: The rate of respiration increases with physical activity. When an organism is more active, such as during exercise, it needs more energy, leading to a faster rate of respiration. For example, a human breathes faster during a race than when sitting.

Size

Surface Area to Volume Ratio: Smaller organisms have a larger surface area relative to their volume, causing them to lose heat more quickly. To compensate for energy lost as heat, small organisms tend to respire faster than larger organisms.

Age

Growth and Energy Needs: Young organisms generally respire faster than older ones. This is because they need more energy for growth, and they are typically more active than older organisms, which also demands higher respiration rates.

Health

Increased Respiration in Illness: When an organism is sick, its metabolism speeds up to remove toxins and waste produced by pathogens. This leads to an increase in the rate of respiration to support the body's defense mechanisms.