Subject: Biological Sciences
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Question 24:
What happens if only Anaerobic Respiration takes place in human beings
?
A) It leads to the death of human beings
B) It leads to more energy production in human beings
C) It leads to sufficient energy production in human beings
D) Nothing problem to human beings
Answers
Answer:
Glycolysis is a metabolic pathway and an anaerobic source of energy that has evolved in nearly all types of organisms. Another name for the process is the Embden-Meyerhof pathway, in honor of the major contributors towards its discovery and understanding.[1] Although it doesn't require oxygen, hence its purpose in anaerobic respiration, it is also the first step in cellular respiration. The process entails the oxidation of glucose molecules, the single most crucial organic fuel in plants, microbes, and animals. Most cells prefer glucose (although there are exceptions, such as acetic acid bacteria that prefer ethanol). In glycolysis, 2 ATP molecules are consumed, with the production of 4 ATP, 2 NADH, and 2 pyruvates per molecule of glucose. The pyruvate can be used in the citric acid cycle or serve as a precursor for other reactions.[2][3][4]
Fundamentals
Glycolysis ultimately splits glucose into two pyruvate molecules. One can think of glycolysis as having two phases, occurring in the cytosol of cells. The first phase is the "investment" phase due to its usage of two ATP molecules, and the second is the "payoff" phase. These reactions are all catalyzed by its own enzyme, with phosphofructokinase being the most essential for regulation as it controls the speed of glycolysis.[1]
Glycolysis occurs in both aerobic and anaerobic states. In aerobic conditions, pyruvate enters the citric acid cycle and undergoes oxidative phosphorylation leading to the net production of 32 ATP molecules. In anaerobic conditions, pyruvate converts to lactate through anaerobic glycolysis. Anaerobic respiration results in the production of 2 ATP molecules.[5] Glucose is a hexose sugar, meaning it is a monosaccharide with six carbon atoms and six oxygen atoms. The first carbon has an attached aldehyde group, and the other five carbons have one hydroxyl group each. During glycolysis, glucose ultimately breaks down into pyruvate and energy; a total of 2 ATP is derived in the process (Glucose + 2 NAD+ + 2 ADP + 2 Pi --> 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O). The hydroxyl groups allow for phosphorylation. The specific form of glucose used in glycolysis is glucose 6-phosphate.
Cellular
Glycolysis occurs in the cytosol of cells. Under aerobic conditions, pyruvate derived from glucose will enter the mitochondria to undergo oxidative phosphorylation. Anaerobic conditions result in pyruvate staying in the cytoplasm and being converted to lactate by the enzyme lactate dehydrogenase.[5]
Molecular
Glucose first converts to glucose-6-phosphate by hexokinase or glucokinase, using ATP, with the addition of a phosphate group. Glucokinase is a subtype of hexokinase found in humans. Glucokinase has a reduced affinity for glucose and is found only in the pancreas and liver, whereas hexokinase is present in all cells. Glucose 6-phosphate is then converted to fructose-6-phosphate, an isomer, by phosphoglucose isomerase. Phosphofructose-kinase then produces fructose-1,6-bisphosphate, using another ATP molecule. Dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate are then created from fructose-1,6-bisphosphate by fructose bisphosphate aldolase. DHAP will be converted to glyceraldehyde-3-phosphate by triosephosphate isomerase, where now the two glyceraldehyde-3-phosphate molecules will continue down the same pathway. Glyceraldehyde-3-phosphate will become oxidized in an exergonic reaction into 1,3-bisphosphoglycerate, with the reduction of an NAD+ molecule to NADH and H+. 1,3-bisphosphoglycerate will then turn into 3-phosphoglycerate with the help of phosphoglycerate kinase, along with the production of the first ATP molecule from glycolysis. 3-phosphoglycerate will then convert, with the help of phosphoglycerate mutase, into 2-phosphoglycerate. Enolase, with the release of one molecule of H2O, will make phosphoenolpyruvate (PEP) from 2-phosphoglycerate. Due to the unstable state of PEP, pyruvate kinase will facilitate its loss of a phosphate group to create the second ATP in glycolysis. Thus, PEP will then undergo conversion to pyruvate.[6][7][8]