1. Metabolism of autotrophs vs. heterotrophs
Autotrophs (also known as producers) are the organisms that can produce their own food (e.g. complex organic compounds) through photosynthesis or chemosynthesis and use later on for metabolic purposes. On the other hand, heterotrophs (also known as consumers) are the organisms that cannot produce their own food rather rely on pre-existed energy sources. Autotrophs use simple inorganic substances such as CO2 and fix them in the presence of sunlight or other free energy sources (e.g. CO2 + H20 + Sunlight -> Glucose, H20). On the other hand, heterotrophs use complex organic compounds produced by autotrophs, breaks them into simpler inorganic compound and obtain stored energy for metabolic purposes (e.g. Glucose + H20 -> CO2 + H20 + Energy).
2. Role of ATP in metabolism
Adenosine triphosphate (ATP) is an energy-carrying molecule or energy currency of the cell because it stores chemical energy produced during cellular respiration. Furthermore, ATP is used to transport chemical energy in many important metabolic processes, for example, fermentation, photosynthesis, glycolysis, protein synthesis, etc.ATP consists of a five-carbon sugar (ribose), a nitrogenous base (adenine), and three phosphate groups. These three phosphate groups are attached by two phosphoanhydride bonds. The phosphoanhydride bonds are high-energy bonds. Energy is released when one high-energy bond break and ATP converts to Adenosine diphosphate molecule (ADP). By breaking the second high-energy bond, ADP converts to Adenosine monophosphate molecule (AMP) and more energy release. This process knows as hydrolysis because it happens in the presence of water.
3. What is fermentation? What is muscle fatigue? How are these related?
Fermentation: Fermentation is a type of energy extraction process (in parallel to respiration) through which carbohydrates (energy rich molecules) are broken down into alcohol or acid in the absence of oxygen (anaerobically) by the action of enzymes.
There are three basic types of fermentation.
Lactic acid fermentationEthyl alcohol fermentationAcetic acid fermentation
Muscle fatigue: In humans and many other aerobic organisms, fermentation occurs during low or no supply of oxygen. Normally, respiration yields energy in these organisms. However, when oxygen supply is limited, body still struggles to generate energy in an alternative path which is defined above as fermentation. The product of this pathway (fermentation) is Lactic Acid in humans and similar animals. Muscle fatigue is the result of this phenomenon where acid accumulates within the muscles and causes fatigue. However, it is important to consider that our bodies are not mainly designed for fermentation thus energy-yielding process via fermentation happens only during forceful exercise.
How fermentation and muscle fatigue are related: When a person is running or exercising, his/her body needs more energy to perform metabolic reactions quickly. However, the uptake of oxygen is limited, which is why lungs respire fast. But, if oxygen is still not enough for the workout to produce sufficient energy, the body will shift to anaerobic respiration (fermentation) during which stored energy in the muscles (glycogen) will be used to yield energy. Nevertheless, this process produces lactic acid produces as an output. Lactic acid continues building around muscles and results in muscle fatigue. This phenomenon is known as a lactic acid fermentation. Therefore, muscle fatigue and Lactic acid fermentation are related to each other.
