Energy Production in Biochemical Pathways: Study with Video Lessons, Practice Problems & Examples

Biochemical systems primarily generate energy through two methods: oxidation reactions and cleavage reactions. Oxidation reactions involve the conversion of substrates like malate to oxaloacetate, producing electron carriers such as NADH and FADH₂. Cleavage reactions, or hydrolysis, release energy by breaking high-energy bonds, exemplified by ATP hydrolysis. Understanding these processes is crucial for grasping energy production in cellular metabolism, highlighting the significance of enzymes like dehydrogenases in oxidation and the role of ATP as an energy currency.

Energy Production In Biochemical Pathways Concept 1

Hey, everyone. So here we can say that biochemical systems most commonly employ 2 methods to produce energy. Now in the first one, we have oxidation reactions. And they produce energy in the form of electron carriers. So we're talking about the production of NADH and FADH₂.

If we take a look here, we have step 8 of our citric acid cycle, where we have malate being changed into oxaloacetate. Here, we have NAD⁺. It's going to gain electrons to become NADH and through the use of our substrate, malate, and our enzyme, malate dehydrogenase, we create oxaloacetate. Remember, when we talk about dehydrogenases as enzymes, we're talking about oxidation reactions. Over here, this represents step 6 of our Citric Acid Cycle where we have succinate being changed into fumarate.

Again, we're using a dehydrogenase, so this is an oxidation that's occurring. In this case, though, we have FAD becoming FADH₂. Remember, FAD to FADH₂ will be utilized in order to create a pi bond. In this case, we created a pi bond between these two carbons which transforms our succinate into fumarate. Now, next, we're gonna say we have what's called cleavage reactions or just simply hydrolysis.

So we're going to have the cleavage or hydrolysis of high energy bonds to release energy stored in them. A great way to look at this is the cleaving of our phosphate bonds in ATP to release energy. So here we have ATP, we include our water, here it's going to help break one of these bonds, releasing an inorganic phosphate. And in the process, because we're breaking that high energy bond, we're gonna release ATP. So here's the ATP that's released.

So just remember, when it comes to these biochemical systems, biochemical reactions, there are mainly 2 major ways to produce energy, either through oxidation reactions or through cleavage slash hydrolysis.

Energy Production In Biochemical Pathways Example 1

Here it says, identify whether the following biochemical reaction would use energy or produce energy. In this reaction, we have isocitrate plus NAD positive. We're using the enzyme isocitrate dehydrogenase. This creates Alpha-Ketoglutarate, Carbon Dioxide, NADH plus H Positive. Now, here, we're going to say that we're using a dehydrogenase.

Remember, this is the enzyme of choice for an oxidation reaction. And we're going to say this is an oxidation reaction because we've produced NADH. Remember these NADH FADH₂ productions for these oxidation reactions will make energy, so this is going to produce energy. And this particular reaction itself represents reaction 3 or step 3 in the Krebs cycle or citric acid cycle. Okay.

So here, because we're using a dehydrogenase, this is an oxidation reaction. We're making NADH, which is an electron carrier. This is indicative of a biochemical reaction that's going to produce energy.

Which of the following biochemical reactions would not produce energy?

• A. ATP + H₂O ⟶ ADP + HOPO₃²⁻ + H⁺
• B. Glycerol-3-phosphate + FAD ⟶ Dihydroxyacetone phosphate + FADH₂
• C. Pyruvate + NAD⁺ + HS–CoA ⟶ Acetyl CoA + CO₂ + NADH
• D. Glucose + ATP ⟶ Glucose-6-phosphate + ADP + H⁺