Difference Between Glycolysis and TCA Cycle

关键区别 - 糖酵解与TCA周期

呼吸是一个占据一系列反应的过程氧化和还原反应and electron transfer. At the end of the respiration, organisms produce energy to utilize for their metabolic processes. This energy is produced in the form ofATP(energy currency of the cells). Duringaerobic respiration，氧分子充当最终电子受体，并减少以产生水。这会产生一个电化学梯度，该梯度驱动ATP合成。有氧呼吸由三个主要阶段组成，其中碳分子通过一系列酶催化反应重新排列以产生ATP。第一阶段（共吸烟和厌氧菌共有）是糖酵解途径，其中糖底物（主要是葡萄糖）被分解为两个丙酮酸分子。这种转换产生两个ATP分子和两个纳德分子。第二阶段是三羧酸（TCA）循环，这是中心枢纽，其中所有代谢途径的中间体通过产生NADH，FADH2和CO的两个分子来促进能量生产。₂via oxidation-reduction reactions. The TCA cycle only takes place in aerobes. In both these processes, substrate level phosphorylation takes place to produce energy. The key difference between glycolysis and TCA cycle is thatglycolysis occurs in the细胞质while the TCA cycle occurs in线粒体.

内容

1.Overview and Key Difference
2.什么是糖酵解
3.What is TCA Cycle
4.Similarities Between Glycolysis and TCA Cycle
5.Side by Side Comparison – Glycolysis vs TCA Cycle in Tabular Form
6.Summary

什么是糖酵解?

糖酵解或Embden-Meyerhof Pathwayis the first step of energy production and takes place in thecytosolof both aerobes and anaerobes. It is an enzyme catalyzed reaction procedure comprising of ten reaction steps. In glycolysis, sugar molecules are phosphorylated and trapped in the cell to catabolize into two丙酮酸molecules (three carbon compound) which are the end products of glycolysis.

糖酵解阶段

It has three main stages as follows:

准备阶段

In this stage, sugar residues which contain six carbon atoms are phosphorylated and trapped in the cell. Preparatory phase is an energy requiring phase where two ATP molecules are utilized.

Cleavage Stage

在此阶段，将6个碳分子裂解成两个磷酸化的3碳残基。

Pay off Stage

这是合成ATP和NADH的糖酵解的最后阶段。对于每6个碳糖基质，产生了4个ATP分子，2个NADH分子和2个丙酮酸分子。因此，这是糖酵解的能量产生阶段。

糖酵解的总体反应

Glucose + 2P_i+ 4ADP + 2NAD⁺+ 2ATP→2丙酮酸 + 4ATP + 2NADH + 2H₂O + 2H⁺

净生产ATP = 2 ATP

什么是TCA周期？

三羧酸循环e, also referred asCitric acid cycle或者Krebs cycle，发生在线粒体的矩阵中。它是有氧呼吸的一部分；因此，它仅发生在健美动物中。TCA循环是一种环状酶催化的途径，其中4-碳底物（草乙酸）接受2-碳乙酰基COA以产生6-碳分子（柠檬酸盐）。柠檬酸盐经历环状代谢途径，产生两个二氧化碳分子，两个NADH分子，一个FADH₂分子和一个GTP分子。TCA循环的主要功能是从碳燃料中收集高能电子。然后将这些高能电子转移到电子传输链上，这是ATP合成的有氧呼吸的最后阶段。TCA循环也是氧化的最终共同途径carbohydrates,amino acids,fatty acids， 和nucleotides. Carbohydrates and fatty acids enter the TCA cycle as Acetyl Coenzyme A whereasamino acids输入TCA周期作为α - 酮谷酸酯和nucleotides作为富马酸。

Overall Reaction of TCA Cycle

Acetyl Co A + 3 NAD⁺+ FAD + GDP + 2P_i+ 2H₂o→2co₂+ 3nadh + fadh₂+ GTP + 3H⁺

What are the Similarities Between Glycolysis and TCA cycle?

• 糖酵解和TCA周期包括一系列酶催化反应。
• In both processes,substrate level phosphorylationtakes place.
• 这两个过程都会产生nadh，h₂O as products.
• Both processes are regulated through hormonal control, allosteric regulation and end product inhibition (feedback mechanisms).

糖酵解和TCA周期有什么区别？

Glycolysis vs TCA Cycle
糖酵解是将6种碳糖（单糖）分子通过酶催化反应分解成3-碳丙酮酸分子的过程。	三羧酸循环e is the process where the energy stored in carbon molecules are harvested to produce electron-rich compounds for electron transport chain to synthesize ATP viaoxidative phosphorylation.
Site of Reaction
Glycolysis occurs in the cytosol.	三羧酸循环e occurs in the matrix of mitochondria.
Requirement of Oxygen
在有氧和厌氧条件下，糖酵解可能发生。	三羧酸循环e is strictly aerobic.
Starting Compound
Six carbon monosaccharide (glucose) is the starting substrate of glycolysis.	四碳草乙酸是TCA循环的起始底物。
最终产品
两个丙酮酸分子，两个ATP分子和两个NADH分子是糖酵解的最终产物。	Two CO2, one GTP, three NADH and one FADH2 are the end products of TCA cycle.
Sequence of Reactions
糖酵解反应作为线性序列出现。	三羧酸循环e occurs via a cyclic sequence.
CO的参与2
在糖酵解过程中不需要或生产二氧化碳。	CO2 is produced for each acetyl co A molecule of TCA cycle.
ATP的消费
2个ATP分子被糖酵解途径消耗。	ATP molecules are not utilized in TCA cycle.

摘要 - 糖酵解与TCA周期

Glycolysis and TCA cycle are two vital metabolic pathways involved in the production of energy via carbon intermediates derived from the macro molecules carbohydrates, proteins, fats and nucleic acids. Both processes are enzyme mediated and are under constant regulation based on the energy requirement of the cell/organism and the rates of these processes differ under various conditions such as the fasting state, well-fed state, starvation state and exercised state. It is important to study the regulation of the glycolytic pathway and the TCA cycle in order to derive biochemical relationships to address metabolic imbalances in the body. Glycolysis is the initiative process of respiration and TCA cycle is the second major phase of aerobic respiration which connects with the final stage of the respiration (electron transport chain). Glycolysis occurs in the cytoplasm and produces pyruvates; these pyruvates enter the mitochondria and aid in TCA cycle. Glycolysis can happen under both aerobic and anaerobic organisms. However, TCA cycle happens only in aerobic organisms since it needs aerobic conditions. This is the difference between glycolysis and TCA cycle.

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References:

1. Berg，JeremyM。“柠檬酸周期。”生物化学。第五版，美国国家医学图书馆，1970年1月1日，在这里可用。Accessed 21 Aug. 2017.
Berg, Jeremy M. “Glycolysis Is an Energy-Conversion Pathway in Many Organisms.” Biochemistry. 5th edition., U.S. National Library of Medicine, 1 Jan. 1970,在这里可用。Accessed 21 Aug. 2017.

Image Courtesy:

1. Wyassinemrabet的“糖酵解” - 自己的作品(CC BY-SA 3.0)viaCommons Wikimedia
2. “Citric acid cycle noi” By Narayanese (talk) – Modified version of Image:Citricacidcycle_ball2.png.(CC BY-SA 3.0)viaCommons Wikimedia