How Many ATP Molecules Could Optimally Be Generated

Introduction

• ATP is a type of energy that powers each cell in your body and keeps it functioning. The biological mechanism for storing and using energy is called adenosine triphosphate (ATP).

• The molecule that carries the most energy in your body is called ATP. In order to power the work in the cell, it first captures the chemical energy included in food molecules.

• Your body's cells use ATP as a standard form of exchange. Your digestive system breaks down the food you eat into tiny macronutrient components. Your diet's carbs are all turned into glucose, a form of simple sugar that must first be changed into ATP (the energy form that will work in the cell).

• The process by which glucose is transformed into ATP involves a complex series of chemical events. Cellular respiration, often known as metabolism, is the process of conversion.

• The energy from glucose is converted into transient chemical molecules at the conclusion of each process, much like the transfer of money from one currency to another.

Key Points

• Despite the fact that glucose catabolism always results in energy production, the amount of energy (measured in ATP equivalents) produced might vary, particularly between different species.

• Between species, different numbers of hydrogen ions can be pumped through the membrane by the electron transport chain complexes.

• NAD+ can cause variations in ATP synthesis and give more ATP than FAD+ in the electron transport chain.

• Lower ATP yields can result from alternative biochemical processes, such as amino acid synthesis.

Key Terms

• Catabolism: a destructive metabolism that typically involves the release of energy and the destruction of materials.

ATP Yield

• One molecule of glucose can be converted into 30 to 32 ATP during the process of cellular respiration in a eukaryotic cell. Only two ATP molecules are created during glycolysis; the rest are produced during the electron transport chain. There is no doubt that the electron transport chain is much more effective, but it can only function when there is oxygen present.

• Through the breakdown of glucose, a variety of ATP molecules can be produced. The capacity of the electron transport chain complexes to pump through the membrane different numbers of hydrogen ions, for instance, varies between species. During the transfer of electrons between mitochondrial membranes, there is yet another source of variation. Because of this, mitochondria cannot easily take up the NADH produced during glycolysis. Electrons are thus detected as a result.

• As a result, NAD+ or FAD+ are responsible for picking up electrons inside the mitochondria. Less ions may be transported by these FAD+ molecules, and as a result, less ATP is produced when FAD+ serves as a carrier. The liver uses NAD+ as an electron transporter, and the brain uses FAD+ as an electron transporter.

• The fact that intermediate chemicals in these pathways are utilised for various functions also influences the yield of ATP molecules produced from glucose. Though the outcome is not always desirable, glucose catabolism interacts with the processes that create or degrade all other biochemical substances in cells. Feeding of carbohydrates other than sugar is one example.

• Additionally, glycolysis intermediates are used to create the five-carbon sugars that make up nucleic acids. From intermediates of both glycolysis and the citric acid cycle, specific non-essential amino acids can be produced. These routes also produce lipids like cholesterol and triglycerides from their intermediates, and they are also used to break down triglycerides and amino acids for energy. About 34% of the energy in glucose is extracted overall by these pathways of glucose catabolism in living systems.

About ATP

• Three phosphates are joined to an adenine nucleotide to form ATP.

• The connection between the second and third phosphate groups contains a significant amount of stored energy that can be used to drive chemical reactions.

• This link is broken by the process of hydrolysis, sometimes referred to as dephosphorylation, when a cell needs energy. Adenosine diphosphate (ADP) and a free phosphate molecule are the results.

• In the above-mentioned procedure, ADP stands for adenosine diphosphonate, and Pi stands for inorganic phosphate.

• ADP can also be converted to ATP in the opposite direction of the reaction.

• Condensation or phosphorylation are two terms used to describe this process. Due to its high instability and rapid hydrolysis, the ATP molecule causes this to occur. In comparison to the ADP molecule, the phosphate group bonds in the ATP molecule are weaker.

ATP Production

• All of the body's cells are involved in the production of ATP. Glucose digestion in the intestines triggers the process to get going. It then enters cells, where it is transformed into pyruvate. The mitochondria of the cells are next on their route. Ultimately, ATP is created there.

• Your body would be bursting at the seams with the energy it couldn't use without the road to ATP generation. The common energy transporter and unit of exchange is ATP. It contains all the energy required for each cell to carry out its functions. Additionally, once ATP is created, it can be used repeatedly, similar to a rechargeable battery.

• The body has a number of distinct processes in place to produce ATP because of how crucial it is. These systems interact in three stages (pathways), including glycolysis, and the Krebs cycle (citric acid cycle).

Glycolysis

• Through a sequence of processes known as glycolysis, glucose is divided into two pyruvate molecules, each of which has three carbons. The vast majority of species alive today have a metabolic process called glycolysis, which is an old metabolic pathway that originated in the distant past.

• Glycolysis is the initial step in the process of cellular respiration in organisms. Although many anaerobic organisms (organisms that do not use oxygen) have this process, glycolysis is not oxygen-dependent.

• The energy-requiring phase and the energy-releasing phase are the two primary stages of glycolysis, which occur in the cytoplasm of a cell.

• Overall: Two three-carbon pyruvate molecules are produced from the glycolysis of one six-carbon glucose molecule. Two molecules of ATP and two molecules of NADH are the net results of this action.

Krebs Cycle or Citric Acid Cycle

The second crucial stage of oxidative phosphorylation is the Krebs cycle, often known as the citric acid cycle. The Krebs cycle converts the energy from the smaller, 3-carbon glucose molecules produced by glycolysis into electron carriers, which are then used in the electron transport chain to create ATP.

• The various Krebs cycle enzymes are located on the inner membrane or in the matrix region of the mitochondria.

• The Krebs cycle within the mitochondrial matrix adds protons and electrons.

• Because energy-rich molecules such as NAD + and FAD can only recover from their reduced forms by transferring electrons to molecule oxygen, this cycle can only occur under aerobic conditions.

• The universal ultimate mechanism for the oxidation of all biomolecules, including proteins, fatty acids, and carbohydrates, is the citric acid cycle.

• The citric acid cycle is a process-long cycle of reactions mediated by eight enzymes.

• This cycle is also crucial because it feeds the electron transport chain with high-energy electrons and molecules that are used to create ATP and water.

• After glycolysis, the pyruvate that is left over is first converted to acetyl CoA and then enters the citric acid cycle.

For every glucose molecule used in the Krebs cycle, two ATP molecules are produced. Per molecule of glucose, the Krebs cycle also generates two molecules of FADH2 and eight molecules of NADH. Later on, energy is generated through electron transport phosphorylation using NADH and FADH2.

Electron Transport Chain

The process by which electrons are transferred to oxygen allows for a gradual reduction in electron energy. The electron transport chain is another name for this phase of oxidative phosphorylation.

An electron is moved from a donor molecule to an acceptor molecule through a sequence of redox events in the electron transport chain. The free energy (energy that can be used for work) of the reactants and products is the fundamental force driving these reactions. Any reaction that lowers a system's overall free energy will take place.

• All areas of life contain the enzyme ATP synthase. A transmembrane proton electrochemical gradient provides its power. The chain of redox reactions led to this outcome. This gradient is created by the electron transport chain. ATP synthesis is fueled by free energy.

• An electron is moved from a donor molecule to an acceptor molecule through a sequence of redox events in the electron transport chain. The free energy (energy that can be used for work) of the reactants and products is the fundamental force driving these reactions. Any reaction that lowers a system's overall free energy will take place.

• All areas of life contain the enzyme ATP synthase. A transmembrane proton electrochemical gradient provides its power. The chain of redox reactions led to this outcome. This gradient is created by the electron transport chain. ATP synthesis is fueled by free energy.

• For electron transport phosphorylation, the NADH and FADH2 generated by the citric acid cycle and glycolysis, respectively, are taken as electron carriers. 32 ATP molecules are created during this procedure.

ATP Uses

There are numerous uses for the ATP molecule. Because it can store a lot of energy that is required in numerous metabolic processes, ATP is a crucial molecule in metabolism.

The process of constructing proteins involves ATP, which is crucial.

• The energy produced by repeated cycles of ATP hydrolysis is used to propel molecular motors.

• It aids in the contraction of muscles.

• It is crucial for the movement of molecules through membranes. Active transport is another name for this procedure.

• Additionally, they are employed in the transmission of signals and the production of DNA.

• ATP plays a crucial role as an extracellular signalling molecule. The central and peripheral nervous systems both use ATP as a neurotransmitter. ATP participates in chemical transmission in the sensory and autonomic ganglia of the peripheral nervous system. The central nervous system generates fast excitatory postsynaptic currents.

Conclusion

• The usual range for cellular ATP concentration is 1 to 10 mmol/L, while the normal ATP/ADP ratio is around 1000.

• A healthy adult has about 0.10 mol/L of ATP overall.

• Each ATP molecule is recycled between 1000 and 1500 times per day, which translates to a daily requirement of 100 to 150 mol/L of ATP.

• In essence, the human body recycles its weight in ATP every day.