TAHAPAN SIKLUS KREBS|Jembatan Keledai

Susi Martiani

10 Nov 202006:09

Summary

TLDRThe script explains the third stage of aerobic cellular respiration, the Krebs cycle, named after its discoverer, Sir Hans Adolf Krebs. It occurs in the mitochondrial matrix and involves eight steps, producing citrate from acetyl-CoA and oxaloacetate. The cycle includes isomerization, decarboxylation, and electron transfer to NAD+ and FAD, resulting in the formation of NADH, FADH2, and ATP. The script details each step, highlighting the enzymes and reactions that lead to the production of energy-rich molecules essential for cellular functions.

Takeaways

🧬 The script discusses the third stage of aerobic cellular respiration, known as the Citric Acid Cycle or Krebs Cycle.
🔬 The cycle is named after Sir Hans Adolf Krebs, a German-British biochemist who discovered it.
🌐 The Citric Acid Cycle occurs in the mitochondrial matrix and is also referred to as the Krebs Cycle or the Tricarboxylic Acid (TCA) Cycle.
🔋 The cycle consists of eight steps, each involving different chemical reactions and enzymes.
🔬 The first step involves the condensation of acetyl-CoA with oxaloacetate to form citrate, releasing CoA in the process.
🔄 Isomerization occurs in the second step, converting citrate to isocitrate, which is catalyzed by the enzyme aconitase.
➖ During the third step, isocitrate is converted to alpha-ketoglutarate, releasing electrons that are captured by NAD+ to form NADH.
🔋 The fourth step involves decarboxylation, reducing the carbon count and producing carbon dioxide, catalyzed by isocitrate dehydrogenase.
🔬 In the fifth step, alpha-ketoglutarate is transformed into succinyl-CoA, which involves the addition of a CoA group and is catalyzed by alpha-ketoglutarate dehydrogenase.
↔️ The sixth step sees the conversion of succinyl-CoA to succinate, with the release of CoA and the formation of GTP or ATP, depending on the cell type.
🔋 The seventh step involves the conversion of succinate to fumarate, with the help of succinate dehydrogenase, and the production of FADH2.
🔄 The final step, catalyzed by malate dehydrogenase, converts malate back to oxaloacetate, completing the cycle and producing NADH.

Q & A

What is the third stage of aerobic cellular respiration called?
-The third stage of aerobic cellular respiration is called the Krebs cycle, also known as the citric acid cycle.
Who is the Krebs cycle named after?
-The Krebs cycle is named after Sir Hans Adolf Krebs, a German and English biochemist.
What is another name for the Krebs cycle?
-The Krebs cycle is also known as the citric acid cycle because it produces citrate.
Where does the Krebs cycle take place within the cell?
-The Krebs cycle takes place in the mitochondrial matrix.
How many stages are there in the Krebs cycle?
-There are eight stages in the Krebs cycle.
What is the first substrate to enter the Krebs cycle?
-The first substrate to enter the Krebs cycle is acetyl-CoA, which is a result of oxidative decarboxylation.
What is the role of isocitrate dehydrogenase in the Krebs cycle?
-Isocitrate dehydrogenase catalyzes the conversion of isocitrate to alpha-ketoglutarate, releasing electrons that are picked up by NAD+ to form NADH.
What is the product of the decarboxylation of alpha-ketoglutarate in the Krebs cycle?
-The product of the decarboxylation of alpha-ketoglutarate is succinyl-CoA.
What is the role of succinate dehydrogenase in the Krebs cycle?
-Succinate dehydrogenase catalyzes the conversion of succinate to fumarate, capturing electrons to form FADH2.
What is the final product of the Krebs cycle?
-The final product of the Krebs cycle is oxaloacetate, which can be used to start the cycle again.
How many ATP molecules are produced per turn of the Krebs cycle?
-One turn of the Krebs cycle produces one ATP (or GTP), three NADH, and one FADH2.

Outlines

00:00

🧬 Krebs Cycle Explained

The first paragraph delves into the third stage of aerobic cellular respiration, known as the Krebs cycle, named after its discoverer, Sir Hans Adolf Krebs. It's also called the citric acid cycle due to the production of citrate. The cycle occurs in the mitochondrial matrix and consists of eight steps involving various chemical transformations. The paragraph details these steps, starting with the condensation of acetyl-CoA with oxaloacetate to form citrate, followed by isomerization, decarboxylation, and electron transfer. Each step is catalyzed by specific enzymes, and the paragraph describes the enzymes and reactions involved in depth. The Krebs cycle results in the production of three NADH, one FADH2, and one ATP per cycle.

05:02

🔋 Energy Yield from the Krebs Cycle

The second paragraph continues the explanation of the Krebs cycle, focusing on the energy yield from the cycle. It mentions that each cycle produces three NADH, one FADH2, and one ATP. The paragraph also discusses the oxidative decarboxylation step, which results in the formation of two acetyl-CoA, leading to the production of six NADH, two FADH2, and two ATP in total. The paragraph concludes by summarizing the overall energy yield from the Krebs cycle.

Mindmap

Keywords

💡Aerobic Respiration

Aerobic respiration is a process that uses oxygen to convert glucose into energy. It's a crucial process for cellular metabolism and is the main theme of the video. The script discusses the third stage of aerobic respiration, the Krebs cycle, which is a key part of this process. The Krebs cycle is where the actual oxidation of acetyl-CoA occurs, leading to the production of energy-rich molecules.

💡Krebs Cycle

The Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid cycle, is a central metabolic pathway that takes place in the mitochondria of cells. It is named after Sir Hans Adolf Krebs, who identified it. The cycle is a series of chemical reactions that generate energy from acetyl-CoA derived from carbohydrates, fats, and proteins. The script details the eight stages of the Krebs cycle, highlighting its importance in cellular respiration.

💡Citrate

Citrate is an organic compound that is a key intermediate in the Krebs cycle. It is formed from the condensation of acetyl-CoA with oxaloacetate, marking the beginning of the cycle. The script mentions citrate as the product of the first reaction in the Krebs cycle, where acetyl-CoA and oxaloacetate combine to form a six-carbon compound.

💡Isocitrate

Isocitrate is a compound formed from citrate during the second stage of the Krebs cycle. The script describes the conversion of citrate to isocitrate through isomerization, which involves the release of a molecule of water (dehydration) and the addition of a water molecule (hydration). This step is catalyzed by the enzyme aconitase.

💡Alpha-Ketoglutarate

Alpha-Ketoglutarate is a five-carbon compound that results from the conversion of isocitrate in the third stage of the Krebs cycle. This step involves the release of electrons that are captured by NAD+ to form NADH, an important energy carrier. The script refers to this compound as a product of the decarboxylation process where one carbon is removed as carbon dioxide.

💡Succinyl-CoA

Succinyl-CoA is a compound that forms during the fourth stage of the Krebs cycle when alpha-ketoglutarate is converted. The script mentions the addition of a coenzyme A to alpha-ketoglutarate, facilitated by the enzyme alpha-ketoglutarate dehydrogenase. This step is significant as it is where another carbon is removed as carbon dioxide.

💡Succinate

Succinate is a compound that is produced from succinyl-CoA during the fifth stage of the Krebs cycle. The script describes this step as involving the release of a high-energy phosphate bond, which can be used to form GTP, an energy-rich molecule equivalent to ATP. The enzyme that catalyzes this conversion is succinyl-CoA synthase.

💡Fumarate

Fumarate is a compound that results from the conversion of succinate during the sixth stage of the Krebs cycle. This step involves the release of electrons that are captured by FAD to form FADH2, another energy carrier. The script mentions that the enzyme succinate dehydrogenase is responsible for catalyzing this reaction.

💡Malate

Malate is a compound that is formed from fumarate during the seventh stage of the Krebs cycle. The script describes this step as involving the addition of water, a process known as hydration. The enzyme that catalyzes this conversion is fumarase. Malate is then converted back to oxaloacetate, completing the cycle.

💡Oxaloacetate

Oxaloacetate is a four-carbon compound that serves as a starting point for the Krebs cycle. It is regenerated from malate during the eighth and final stage of the cycle. The script mentions that the enzyme malate dehydrogenase plays a role in this step, which also involves the production of NADH. Oxaloacetate is essential for the continuation of the cycle.

💡NADH and FADH2

NADH and FADH2 are energy-rich electron carriers produced during the Krebs cycle. They carry electrons that are eventually used in the electron transport chain to produce ATP. The script mentions that each cycle of the Krebs cycle produces three NADH molecules, one FADH2 molecule, and one ATP (or GTP). These molecules are critical for cellular energy production.

Highlights

The Streets is the third stage of aerobic cell respiration, known as the Krebs cycle or citric acid cycle.

Krebs cycle is named after its discoverer, Sir Hans Adolf Krebs, a German-English biochemist.

The cycle takes place in the mitochondrial matrix.

There are eight stages in the Krebs cycle.

The cycle involves the conversion of citrate to isocitrate.

Isocitrate undergoes isomerization to form alpha-ketoglutarate.

Alpha-ketoglutarate is converted to succinyl-CoA, releasing electrons that are captured by NAD+ to form NADH.

Succinyl-CoA is then transformed into succinate.

Succinate is converted to fumarate, involving the release of electrons captured by FAD to form FADH2.

Fumarate is then transformed into malate.

Malate is converted back to oxaloacetate, completing the cycle.

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

In the oxidative decarboxylation phase, two acetyl-CoA are produced, leading to the generation of two more ATP.

The cycle is essential for cellular respiration, providing energy for the cell.

Each stage of the cycle is catalyzed by a specific enzyme, ensuring the process is efficient.

The Krebs cycle is a key component of the metabolic pathway, linking glycolysis and the electron transport chain.

The cycle's efficiency is critical for maintaining cellular energy levels and overall metabolic health.