ATP and Energy: Study with Video Lessons, Practice Problems & Examples

ATP, or Adenosine Triphosphate, is a high-energy molecule that stores and transports energy within biological systems. Energy is released through hydrolysis, breaking down ATP into ADP (Adenosine Diphosphate) and a phosphate group. Coupled reactions involve linking unfavorable reactions with favorable exothermic ones, often utilizing ATP hydrolysis to drive these processes. For example, ATP hydrolysis can provide the energy needed to convert glucose into glucose 6-phosphate, demonstrating the critical role of ATP in metabolic pathways.

Adenosine Triphosphate Concept 1

Everyone. In this video, let's take a look at ATP and energy. We know that when it comes to the idea of energy, ATP is one of the most commonly thought of substances or molecules within biological systems. Now, here we're going to say that ATP stands for Adenosine Triphosphate. We're going to say energy obtained from food catabolism is stored in these ATP molecules.

ATP itself is a high energy compound that stores and transports energy. We're going to say it has high-energy phosphorus-oxygen bonds, and hydrolysis of ATP is what yields this energy. If we take a look here, we have ATP. ATP has the adenosine portion, which here is our ribose sugar with our nitrogenous base, which is adenine, and then triphosphate is just 3 phosphate groups connected to our ribose sugar. Collectively, it is ATP.

Now, here when we talk about hydrolysis, we're just adding water, which is going to sever one of these phosphorus-oxygen bonds. Cutting that high-energy bond releases energy. So we've lost 1 phosphate group, so we're no longer triphosphate; instead, we are diphosphate. So we're adenosine diphosphate now. Here is the phosphate group that got cleaved off, and then we've broken that phosphorus-oxygen bond and that is what releases this energy.

Now here's something we should take note of, is that hydrolysis of ADP can happen as well. If we do that, it would produce here our AMP, which is Adenosine Monophosphate, and that would also release energy as well. Right? So just remember, when we talk about energy, ATP is close behind to this. We're going to say, by cleaving these phosphorus-oxygen bonds, we're able to release energy.

Adenosine Triphosphate Example 1

Which components make up the structure of ATP? Remember, ATP stands for Adenosine Triphosphate. The adenosine portion is made up of two things. It's made up of our nitrogenous base in the form of Adenine and the ribose sugar. And if we look, only A and B or A and C have those options.

So B is out, and D is out. So together, those two components make up the adenosine part of ATP. And why is it called triphosphate? Well, triphosphate. There are three phosphate groups connected together.

So here, it would not be one phosphate group; that would be adenosine monophosphate. So by elimination, C would have to be our answer. We're going to say here that ATP, its components are adenine, which is a nitrogenous base again, the ribose sugar, which is our sugar component, together they're the adenosine portion, adenosine, and then we have our three phosphate groups. So, C would be our final answer.

Coupled Reactions Concept 2

Everyone, in our continued discussion of ATP and Energy, let's take a look at coupled reactions. We're going to say not every reaction in metabolic pathways is favorable. They need to be coupled; we need to couple the unfavorable ones with favorable exothermic reactions. Remember, in an exothermic reaction, we are releasing energy in the form of heat.

In this case, we're talking about exothermic in the form of still just releasing energy overall. This can be accomplished through a process such as ATP hydrolysis. It serves as an energy source to drive unfavorable reactions. So, if we take a look here on the left side, this represents an unfavorable reaction. We have our glucose molecule in its cyclic form.

Here we have our phosphate group. What we're trying to do is replace this OH group with our phosphate group to create this structure, glucose 6-phosphate. This reaction is not favorable. It's hard to do that. So what we do instead, in order to make it a favorable reaction, we would first do ATP hydrolysis where we use water.

Remember, ATP hydrolysis, we would cleave one of the phosphorus-oxygen bonds, changing ATP to ADP. We've released the phosphate group, and cleaving that phosphorus-oxygen bond releases energy. We would take that energy, harness it, and use it to attach a phosphate group to this 6 carbon here. And in that way, we can create Glucose 6-Phosphate. Alright.

So, we changed an unfavorable reaction by first doing a more favorable reaction, harnessing that energy, and using it to drive this unfavorable reaction. That's what we mean by a coupled reaction.

Coupled Reactions Example 2

What role does ATP play? Alright, so ATP here through hydrolysis will release energy. This energy can be used to help drive this unfavorable reaction. Here we're going to say, it's going to transfer energy to drive the endothermic reaction. So option a is the best answer.

Here, to act as a catalyst, no. It's not acting as a catalyst. It's acting as an energy source. Speeds up the rate of the reaction. Well, here both options b and c are saying the same thing.

Speeding up the rate of the reaction would mean it's acting as a catalyst, which is not what it's doing. A catalyst speeds up a reaction by lowering the energy of activation. It doesn't change an unfavorable reaction to a favorable one. That's why it doesn't work, and it's not a good option. Absorb energy from the surroundings? No. If we're cutting or cleaving a phosphorus-oxygen bond, we're releasing energy, and then we can use that energy to drive our next reaction. So here option a is the correct answer.