ATP - Online Tutor, Practice Problems & Exam Prep

Adenosine triphosphate (ATP) is a high-energy molecule essential for cellular activities, consisting of three phosphate groups, a pentose sugar, and an adenine base. Energy is released through ATP hydrolysis, converting ATP to adenosine diphosphate (ADP) and a phosphate group. This energy coupling allows exergonic reactions, like ATP hydrolysis, to drive endergonic reactions requiring energy input. Phosphorylation, the transfer of a phosphate group from ATP, can activate or alter target molecules, influencing their function. Understanding these processes is crucial for grasping cellular energy dynamics and metabolic pathways.

ATP

In this video, we're going to begin our lesson on ATP. Now recall from our previous lesson videos that ATP is really just an abbreviation for a molecule called adenosine triphosphate, where the a in ATP is for the a in adenosine, the t in ATP is for the t in tri, and the p in ATP is for the p in phosphate. Adenosine Triphosphate or ATP is a high energy molecule that's used to power cellular activities. If the cell has a lot of ATP, then the cell has a lot of energy, but if the cell has a little bit of ATP, then the cell only has a little bit of energy. There are only 3 primary components of an ATP molecule, and as its name implies with the triphosphate part, tri meaning 3, there is a chain of 3 phosphate groups in an ATP molecule.

The adenosine part of ATP refers to a molecule that has two components: it has a pentose sugar, and it also has an adenine nitrogenous base. Let's take a look at our image down below over here on the left-hand side to get a better understanding of the 3 components of adenosine triphosphate or ATP. The triphosphate part refers to a chain of 3 phosphate groups that you see here, 1, 2, and 3. We can go ahead and label these as phosphate groups, and there are, in fact, 3 phosphate groups on an ATP molecule.

The adenosine portion of ATP actually refers to both the sugar and this nitrogenous base. Here is a pentose sugar, and there is also a nitrogenous base, which is the nitrogenous base of adenine. Together, the adenine nitrogenous base and the pentose sugar make up the adenosine portion of ATP. What's also important to note is that ATP is a high-energy molecule, but the way that cells extract the energy from ATP is through a process called ATP hydrolysis. ATP hydrolysis is the process of breaking bonds between phosphate groups in an ATP molecule that ends up generating chemical energy used by the cell, as well as ADP or adenosine diphosphate, where the d stands for di, meaning that it only has 2 phosphate groups.

In some scenarios, ADP can also be hydrolyzed to form AMP, where the m refers to mono, adenosine monophosphate, and mono is a prefix that means just 1 phosphate. Let's take a look at our image down below over here on the right-hand side to get a better understanding of ATP and ADP hydrolysis. Notice that at the very top, we're starting with an ATP molecule. Here is the adenosine, the nitrogenous base, and the pentose sugar represented in green. The 3 phosphate groups are right here, 1, 2, and 3. ATP can also be represented by this symbol. If we hydrolyze ATP, using water to break down the bonds between phosphate groups, you can see that water is used to break the bonds between phosphate groups. When we break off this bond using water, ultimately, one of the phosphate groups is released, and energy is also released. This energy can be used to power other chemical reactions and cellular activities. The molecule that remains only has 2 phosphate groups, thus it is now ADP since the d stands for diphosphate. ADP can be hydrolyzed, releasing water to break this bond, which releases the phosphate group and energy, forming the AMP molecule, which has only 1 phosphate group. The hydrolysis leads to the release of energy, which powers chemical reactions. This concludes our brief introduction to ATP, and we'll be able to get more practice applying these concepts and learning more about ATP as we move forward in our course. See you all in our next video.

Which of the following statements is true?

• A. ADP contains more potential energy than ATP.
• B. Following hydrolysis, ATP can give off one phosphate group and usable energy, whereas ADP cannot.
• C. The energy produced by ATP comes from the breaking of the bond between two phosphate groups.
• D. AMP and ADP contain the same amount of potential energy.

Which of the following is the most correct interpretation of the figure?

• A. Energy from food sources can be used directly for performing cellular work.
• B. ADP + Pi are a set of molecules that store energy.
• C. ATP is a molecule that acts as an intermediary to store energy for cellular work.
• D. Pi acts as a shuttle molecule to move energy from ATP to ADP.

Energy Coupling

In this video, we're going to introduce energy coupling. Energy coupling is essentially when energy released by an exergonic reaction is used to power or drive an endergonic reaction that requires an energy input. Recall from our last lesson video that ATP hydrolysis is a reaction that is an exergonic reaction. ATP hydrolysis releases energy into the environment. ATP hydrolysis is usually what's going to be coupled to endergonic reactions because the released energy from ATP hydrolysis is used to provide the energy input that those endergonic reactions need to proceed.

Let's take a look at our image down below to get a better feel for energy coupling. Notice on the left-hand side, we're showing you this pizza, because a lot of the energy that we get is from the foods that we end up eating. When we eat pizza, the pizza is going to have all different kinds of molecules in it. It's going to have carbohydrates, proteins, lipids, and more. These molecules in the foods that we eat end up providing energy for our bodies.

Our bodies are going to perform exergonic reactions to essentially break down the foods. Here, we’re showing you the reaction for exergonic reactions. They start with large food molecules and break them down into smaller components, ultimately allowing for converting the energy that's in food into chemical energy in the form of ATP. This energy is going to be used to make ATP. Once ATP is made, then the cell can perform ATP hydrolysis.

In this box, you can see the reactants that are needed for ATP hydrolysis to occur. They're going to need ATP and water. ATP hydrolysis is going to be an exergonic reaction. When ATP is hydrolyzed, it is going to release a lot of energy, as we can see here being released, and also, it's going to end up creating a phosphate group as well as ADP. But this energy that is released is really important and this is where the energy coupling comes into play because ATP hydrolysis is an exergonic reaction that releases energy, and this energy is going to be used directly to provide the energy input that's needed for an endergonic reaction, like what you see here.

Using smaller molecules to build larger molecules and also using ATP, the energy released by ATP in order to create kinetic energy, such as when you're riding your bicycle, the energy that's essentially being used is coming from ATP hydrolysis. ATP hydrolysis is going to create ADP and a phosphate group, and these are really the reactants needed for ATP formation or ATP production. You can see that ATP production, the energy that's going to be added into ADP, is going to come directly from the energy in foods that we eat. Ultimately here, what you can see is that with energy coupling, the movements that we have, the kinetic energy that we need to ride a bike, is ultimately going to be derived directly by ATP hydrolysis. ATP hydrolysis has ATP whose energy comes directly from the foods that we eat, breaking down the foods that we eat.

Ultimately, it's the foods that we eat that can be traced to providing the energy for our movements and muscle contractions. Here, exergonic reactions are used to power endergonic reactions, and this is the idea of energy coupling. This here concludes our introduction to energy coupling, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

How does ATP participate in energy-coupling reactions?

• A. Hydrolysis of ATP fuels endergonic reactions.
• B. Hydrolysis of ADP fuels endergonic reactions.
• C. Synthesis of ATP fuels exergonic reactions.
• D. Synthesis of ADP fuels exergonic reactions.

Phosphorylation

In this video, we're going to introduce Phosphorylation. Phosphorylation refers to the transfer of a phosphate group from ATP to another molecule to provide energy. Phosphorylation by ATP hydrolysis can have a wide variety of effects, including activating a target molecule so that it's capable of reacting and changing the conformation of a target protein. Notice in the image below, we show a glucose molecule as a green hexagon, depicted as the inactive form of glucose, unable to react. However, after ATP hydrolysis and the phosphorylation of the glucose molecule, where phosphorylation is the transfer of a phosphate group from ATP to another molecule, this phosphorylated form of glucose becomes active and capable of reacting.

Notice that adenosine triphosphate, ATP, has three phosphates, whereas ADP only has two phosphates. The third phosphate was transferred over to glucose, as illustrated. This form of glucose is the active form and can proceed to react. Phosphorylation does not always lead to activation of a target molecule; this is just an example of what phosphorylation can achieve.

Remember, phosphorylation leads to a wide variety of effects. In some scenarios, it will lead to activation, but in other scenarios, it could lead to inactivation. The idea here is that phosphorylation can have a wide variety of effects. Over here on the right-hand side, we're focusing on a protein. This red circle represents a protein. Notice that after ATP hydrolysis and phosphorylation of the protein, the protein takes on a completely different conformation, changing its shape, structure, and likely its function as well. You can see the phosphorylated protein here has an altered conformation.

This concludes our introduction to phosphorylation and how ATP is usually the source of the phosphate group in phosphorylation. Phosphorylation can lead to a wide variety of effects, including activating a target to react and changing the conformation of a target protein.

So, this concludes our lesson, and I'll see you guys in our next video.

Here’s what students ask on this topic:

What is ATP and why is it important for cellular activities?

ATP, or adenosine triphosphate, is a high-energy molecule crucial for cellular activities. It consists of three phosphate groups, a pentose sugar, and an adenine base. ATP is important because it stores and provides energy for various cellular processes. When ATP is hydrolyzed, it releases energy by converting to adenosine diphosphate (ADP) and a free phosphate group. This released energy powers cellular activities such as muscle contractions, active transport, and biochemical reactions. Without ATP, cells would not have the energy required to maintain their functions and sustain life.

How does ATP hydrolysis release energy?

ATP hydrolysis releases energy through the breaking of the bond between the second and third phosphate groups in the ATP molecule. This process involves the addition of a water molecule (hydrolysis), which cleaves the bond and results in the formation of ADP (adenosine diphosphate) and an inorganic phosphate (Pi). The chemical equation for ATP hydrolysis is:

${\mathrm{ATP}}_{}+H_2\to {\mathrm{ADP}}_{}+P_i+\mathrm{energy}$

The energy released during this reaction is used to power various cellular processes, making ATP a vital energy currency in cells.

What is the role of ATP in energy coupling?

In energy coupling, ATP plays a crucial role by linking exergonic and endergonic reactions. Exergonic reactions release energy, while endergonic reactions require an energy input. ATP hydrolysis is an exergonic reaction that releases energy, which can then be used to drive endergonic reactions. For example, the energy released from ATP hydrolysis can be used to synthesize macromolecules, transport substances across cell membranes, or perform mechanical work like muscle contractions. This coupling ensures that energy released from catabolic processes is efficiently used to power anabolic processes, maintaining cellular function and homeostasis.

What is phosphorylation and how does it affect target molecules?

Phosphorylation is the process of transferring a phosphate group from ATP to another molecule. This transfer can activate or deactivate the target molecule, alter its function, or change its conformation. For instance, phosphorylation can activate enzymes, making them capable of catalyzing reactions. It can also change the shape of proteins, affecting their activity and interactions with other molecules. Phosphorylation is a key regulatory mechanism in cells, influencing various processes such as signal transduction, metabolism, and cell cycle progression.

What are the components of an ATP molecule?

An ATP molecule consists of three main components: three phosphate groups, a pentose sugar (ribose), and an adenine nitrogenous base. The three phosphate groups are linked in a chain, with high-energy bonds between them. The pentose sugar, ribose, is a five-carbon sugar that forms the backbone of the molecule. The adenine base is a nitrogenous base that pairs with the ribose to form adenosine. Together, these components make ATP a high-energy molecule essential for cellular activities.