Please place the following steps of aerobic cellular respiration in order.
1. Glycolysis
2. Pyruvate oxidation
3. Citric acid cycle (Krebs cycle)
4. Electron transport chain
The steps of aerobic cellular respiration can be placed in the following order:
1. Glycolysis: This is the first step of cellular respiration, and it occurs in the cytoplasm of the cell. Glucose is broken down into two molecules of pyruvate, producing a small amount of ATP and NADH.
2. Transition reaction: This step follows glycolysis and takes place in the mitochondria. Pyruvate is converted into Acetyl-CoA, generating more NADH in the process.
3. Krebs cycle (Citric Acid Cycle): Also known as the TCA cycle (tricarboxylic acid cycle), this step occurs in the mitochondria and completes the breakdown of glucose. Acetyl-CoA enters the cycle and undergoes a series of chemical reactions, producing ATP, NADH, and FADH2.
4. Electron Transport Chain (ETC): This is the final step of aerobic respiration and takes place in the inner mitochondrial membrane. NADH and FADH2 from the previous steps transfer their electrons to the electron transport chain, which creates a proton gradient. This gradient is used to produce ATP through a process called oxidative phosphorylation.
It is important to note that these steps are a simplified overview of cellular respiration and that there are additional complex biochemical reactions involved.
To place the steps of aerobic cellular respiration in order, you can follow these steps:
1. Glycolysis: This is the first step of aerobic cellular respiration, which takes place in the cytoplasm. Glucose, a 6-carbon molecule, is split into two molecules of pyruvate, a 3-carbon molecule. This step also produces a small amount of ATP and NADH.
2. Pyruvate Decarboxylation: After glycolysis, each pyruvate molecule enters the mitochondria, where it is decarboxylated. During this step, a carbon dioxide molecule is removed from each pyruvate, resulting in the formation of acetyl-CoA. This step also generates NADH.
3. Citric Acid Cycle (also known as Krebs cycle or TCA cycle): Acetyl-CoA enters the citric acid cycle, which takes place in the mitochondria. Acetyl-CoA combines with a 4-carbon molecule to form citrate, initiating a series of enzyme-catalyzed reactions. This cycle generates ATP, NADH, FADH2, and releases carbon dioxide.
4. Electron Transport Chain (ETC): NADH and FADH2, produced during glycolysis, pyruvate decarboxylation, and the citric acid cycle, donate their electrons to the electron transport chain. This process takes place in the inner mitochondrial membrane. As electrons pass through the chain, energy is used to pump protons across the membrane, creating a proton gradient. This gradient drives ATP synthesis through chemiosmosis.
5. Chemiosmosis and ATP Synthesis: As protons flow back across the mitochondrial membrane through ATP synthase, ATP molecules are produced. This process is referred to as chemiosmosis and is the final step of aerobic cellular respiration. Oxygen acts as the final electron acceptor in the ETC, combining with electrons and protons to form water.
So, the correct order of steps for aerobic cellular respiration is:
1. Glycolysis
2. Pyruvate Decarboxylation
3. Citric Acid Cycle
4. Electron Transport Chain
5. Chemiosmosis and ATP Synthesis