Bagaimanakah tahapan Siklus Krebs atau Siklus Asam Sitrat?

Biologi Aja!

13 Apr 202006:18

Summary

TLDRThis video script delves into the Krebs cycle, the third stage of aerobic respiration following the oxidative decarboxylation process. Named after its discoverer, Hans Krebs, the cycle occurs in the mitochondrial matrix and consists of eight steps. It involves the conversion of acetyl-CoA into citrate, isocitrate, and other intermediates, ultimately producing CO2, NADH, FADH2, and ATP. The script also highlights the enzymes involved at each stage and ends with a promotion for a learning scholarship from SekolahMu, urging viewers to subscribe and follow for educational benefits.

Takeaways

🌟 The script discusses the Krebs cycle, also known as the citric acid cycle, which is the third stage of aerobic respiration following the oxidative decarboxylation process.
🔍 The Krebs cycle is named in honor of Hans Krebs, a German scientist who discovered this metabolic pathway.
📍 The cycle occurs in the mitochondrial matrix and involves the conversion of acetyl-CoA into various intermediate compounds, resulting in the production of energy.
🔬 The cycle begins with the condensation of acetyl-CoA with oxaloacetate to form citrate, releasing CoA in the process.
♻️ Citrate undergoes isomerization to isocitrate, involving the release and addition of water molecules, catalyzed by the enzyme aconitase.
🔋 Isocitrate is then converted to alpha-ketoglutarate, releasing electrons that reduce NADP+ to NADPH.
🔄 Alpha-ketoglutarate is further oxidized to succinyl-CoA, with the release of one carbon as CO2 and the formation of NADH.
🚀 Succinyl-CoA is converted to succinate, involving the synthesis of ATP through substrate-level phosphorylation.
🌀 Succinate is oxidized to fumarate, capturing electrons that form FADH2.
🔄 Fumarate is then hydrated to malate, which is oxidized back to oxaloacetate, completing the cycle and generating additional NADH.
🔑 The cycle produces three NADH, one FADH2, and one ATP per turn, with the oxidative decarboxylation process contributing additional NADH and FADH2 for the electron transport chain.

Q & A

What is the Krebs cycle, and why is it also known as the citric acid cycle?
-The Krebs cycle, also known as the citric acid cycle, is the third stage in the aerobic respiration process. It is named in honor of Hans Krebs, a German scientist who discovered the cycle. It is also called the citric acid cycle because citric acid is the first compound formed in the cycle.
Where does the Krebs cycle take place within a cell?
-The Krebs cycle takes place in the matrix of the mitochondria.
What is the first compound formed in the Krebs cycle, and what is its role?
-The first compound formed in the Krebs cycle is citrate, which is a six-carbon compound resulting from the condensation of acetyl-CoA with oxaloacetate. Citrate is crucial as it initiates the cycle.
What happens during the conversion of citrate to isocitrate in the Krebs cycle?
-During the conversion of citrate to isocitrate, a water molecule is removed in a dehydration reaction, and another water molecule is added in a hydration reaction, catalyzed by the enzyme aconitase.
What is the role of isocitrate dehydrogenase in the Krebs cycle?
-Isocitrate dehydrogenase catalyzes the conversion of isocitrate to alpha-ketoglutarate, releasing one carbon atom as CO2 and reducing NAD+ to NADH.
How does the Krebs cycle contribute to the production of ATP?
-The Krebs cycle contributes to ATP production by generating high-energy electron carriers (NADH and FADH2) and directly producing one molecule of ATP through substrate-level phosphorylation.
What is the significance of the reduction of NADP+ to NADPH during the Krebs cycle?
-The reduction of NADP+ to NADPH is significant as it provides a means for cells to store high-energy electrons that can be used in biosynthetic pathways, such as fatty acid synthesis.
What is the role of succinyl-CoA synthase in the Krebs cycle?
-Succinyl-CoA synthase catalyzes the conversion of succinyl-CoA to succinate, and in the process, it helps generate one molecule of ATP through substrate-level phosphorylation.
How does the conversion of malate to oxaloacetate in the Krebs cycle contribute to the cycle's continuation?
-The conversion of malate to oxaloacetate by malate dehydrogenase regenerates the starting compound of the cycle, oxaloacetate, allowing the cycle to continue and maintain the flow of metabolites.
What are the total number of NADH, FADH2, and ATP molecules produced per turn of the Krebs cycle?
-Each turn of the Krebs cycle produces three molecules of NADH, one molecule of FADH2, and one molecule of ATP.
How does the Krebs cycle relate to the oxidative decarboxylation process discussed in the previous video?
-The Krebs cycle follows the oxidative decarboxylation process, where the two acetyl-CoA molecules produced from pyruvate are used to start the Krebs cycle, linking glycolysis and the citric acid cycle.

Outlines

00:00

🧬 Krebs Cycle Overview

The first paragraph introduces the Krebs cycle, also known as the citric acid cycle, as the third stage of aerobic respiration following the oxidative decarboxylation process. It highlights the discovery by German scientist Hans Krebs and explains that the cycle occurs in the mitochondrial matrix. The summary details the eight stages of the cycle, starting with the condensation of acetyl-CoA with oxaloacetate to form citrate, a six-carbon compound. It then describes the release of CoA and the subsequent reactions involving isocitrate, alpha-ketoglutarate, and the release of carbon dioxide and electrons that are captured by NAD+ and FAD. The paragraph also mentions the role of various enzymes and the energy production in the form of ATP, NADH, and FADH2.

05:01

🌿 Completing the Krebs Cycle

The second paragraph continues the explanation of the Krebs cycle, detailing the conversion of malate back to oxaloacetate and the formation of NADH. It emphasizes the hydration process and the role of malate dehydrogenase in this stage. The summary outlines the completion of the cycle, which results in the production of three NADH, one FADH2, and one ATP per cycle. It also provides information on the total yield of the Krebs cycle in relation to the oxidative decarboxylation process, which produces six NADH, two FADH2, and two ATP molecules. The paragraph concludes with a call to action for viewers to visit the 'Sekolahmu' website, download their app, and take advantage of a scholarship program for learning, using a provided code for a 50% discount.

Mindmap

Keywords

💡Krebs Cycle

The Krebs Cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins into carbon dioxide and chemical energy in the form of adenosine triphosphate (ATP). In the script, the Krebs Cycle is the main focus of the video, detailing its role as the third stage of aerobic respiration following the oxidative decarboxylation process.

💡Oxidative Decarboxylation

Oxidative decarboxylation is a metabolic process in which a molecule is decarboxylated (loses a carboxyl group) and simultaneously oxidized. In the script, it is mentioned as the process that precedes the Krebs Cycle, where acetyl-CoA is produced from pyruvate, releasing carbon dioxide and providing the starting material for the Krebs Cycle.

💡Mitochondria

Mitochondria are double-membraned organelles found in eukaryotic cells known as the 'powerhouses' of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. In the script, the Krebs Cycle is stated to occur within the mitochondrial matrix, emphasizing its role in cellular respiration.

💡Citrate

Citrate is a key intermediate in the Krebs Cycle, formed by the condensation of acetyl-CoA with oxaloacetate. The script describes citrate as a six-carbon compound that is produced during the first step of the cycle, highlighting its importance in the initial stage of the cycle.

💡Isocitrate

Isocitrate is an intermediate in the Krebs Cycle that is formed from citrate. The script mentions isocitrate as the compound that undergoes isomerization, changing its structure while retaining the same molecular formula, which is a part of the second step in the cycle.

💡Dehydrogenase

Dehydrogenase is an enzyme that catalyzes the removal of electrons (dehydrogenation) from a substrate. In the script, isocitrate dehydrogenase is specifically mentioned as the enzyme that catalyzes the conversion of isocitrate to alpha-ketoglutarate, involving the release of electrons that are accepted by NAD+.

💡Alpha-Ketoglutarate

Alpha-Ketoglutarate is an intermediate in the Krebs Cycle that is formed from isocitrate. The script describes the conversion process, where one carbon is released as carbon dioxide and the remaining five-carbon compound is alpha-ketoglutarate, indicating a key step in the cycle involving decarboxylation.

💡Succinyl-CoA

Succinyl-CoA is a thiol ester derived from the reaction of succinyl-CoA synthetase with GDP and inorganic phosphate, forming GTP (or ATP in some cells). The script explains the role of succinyl-CoA synthetase in the energy production within the Krebs Cycle, where it catalyzes a substrate-level phosphorylation to produce GTP or ATP.

💡Fumarate

Fumarate is an intermediate in the Krebs Cycle formed from malate by the enzyme fumarase. The script mentions the hydration of fumarate, where water is added to the molecule, illustrating the reversible nature of some steps in the cycle.

💡NADH and FADH2

NADH and FADH2 are electron carriers that play a crucial role in the electron transport chain, which is the final stage of cellular respiration. The script explains that the Krebs Cycle produces NADH and FADH2, which then transfer their electrons to the electron transport chain to generate ATP.

💡ATP

ATP, or adenosine triphosphate, is the primary energy currency of the cell. The script discusses the production of ATP during the Krebs Cycle, highlighting the role of substrate-level phosphorylation in generating ATP from GTP or through the electron transport chain using NADH and FADH2.

Highlights

The Krebs cycle, also known as the citric acid cycle, is the third stage in the process of aerobic respiration following the oxidative decarboxylation process.

The cycle is named in honor of Hans Krebs, a German scientist who discovered it.

The Krebs cycle takes place in the mitochondrial matrix.

The cycle consists of eight stages starting with the condensation of acetyl-CoA with oxaloacetate to form citrate.

Citrate, a six-carbon compound, is formed as a result of the first stage of the cycle.

Coenzyme A is released during the formation of citrate.

Isocitrate is formed in the second stage through isomerization, still maintaining a six-carbon structure.

Two reactions occur in this stage: dehydratation and hydration.

In the third stage, isocitrate is converted to alpha-ketoglutarate, releasing electrons that are accepted by NAD+ to form NADH.

Alpha-ketoglutarate, a five-carbon compound, is transformed into succinyl-CoA in the fourth stage, releasing CO2 and reducing NAD+ to NADH.

In the fifth stage, succinyl-CoA is converted to succinate, involving the release of CoA and the formation of GTP or ATP.

Succinate is then converted to fumarate in the sixth stage, capturing electrons to form FADH2.

Fumarate is converted to malate in the seventh stage through the addition of water.

In the final stage, malate is converted back to oxaloacetate, completing the cycle and generating NADH.

The Krebs cycle produces three NADH, one FADH2, and one ATP per cycle.

In conjunction with the oxidative decarboxylation process, the Krebs cycle results in the production of six NADH, two FADH2, and two ATP.

The video concludes with a call to visit the Sekolahmu website and download the app for educational resources and a 50% discount code.

Viewers are also encouraged to subscribe to the Sekolahmu Indonesia channel and follow their social media accounts.