ATP - Online Tutor, Practice Problems & Exam Prep

Adenosine triphosphate (ATP) is a high-energy molecule essential for cellular activities, consisting of adenosine and three phosphate groups. Energy is released through ATP hydrolysis, converting ATP to adenosine diphosphate (ADP) and a phosphate group. This energy coupling drives endergonic reactions, such as muscle contractions. 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 metabolism and energy dynamics.

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. As its name implies with the triphosphate part, tri meaning 3, there are a chain of 3 phosphate groups in an ATP molecule. The adenosine part of ATP is referring to a molecule that actually has 2 components: a pentose sugar and an adenine nitrogenous base.

Let's take a look at our image down below here on the left-hand side to get a better understanding of the three components of adenosine triphosphate or ATP. The triphosphate part is referring to a chain of 3 phosphate groups that you see here, 1, 2, and 3. We can label these as phosphate groups, and there are in fact 3 phosphate groups on an ATP molecule. The adenosine portion of ATP is referring to both this sugar and this nitrogenous base. You can see that there is a pentose sugar here, which is this portion right here, and there's also a nitrogenous base right here, 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 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 that can be used by the cell as well as ADP, or adenosine diphosphate, where the 'd' here stands for di, meaning that it only has 2 phosphate groups. In some scenarios, ADP can also be hydrolyzed to form AMP, or adenosine monophosphate, and the 'm' here is referring to mono, meaning just 1 phosphate. Let's take a look at our image down below here on the right-hand side to get a better understanding of ATP and ADP hydrolysis. Notice that at the very top here, we're starting with an ATP molecule. The pentose sugar is represented right here in green. Then, the 3 phosphate groups are right here, 1, 2, and 3. When we take ATP and hydrolyze it using water to break down the bonds between phosphate groups. When we break off this bond right here between the phosphate group using water, ultimately, one of the phosphate groups is released and also energy is released. This energy can be used to power other chemical reactions and cellular activities. The molecule that remains only has 2 phosphate groups here and so this molecule is now ADP since the 'd' here stands for diphosphate. Di is a root that means only 2 phosphates, one right here and the other one right here. The third one is released or attached to some other molecule. In the process, a lot of energy is released. Again, in some scenarios, ADP, this molecule here, can be also hydrolyzed releasing the phosphate group and also releasing energy as well and the AMP molecule is gonna be made here. And again, the 'M' in AMP is for mono, and mono means only 1 phosphate group. This hydrolysis leads to the release of energy which is used to power chemical reactions.

This here concludes our brief introduction to ATP and we'll be able to get some more practice applying these concepts and learning more about ATP as we move forward in our course. I'll 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.

• 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 + P_i 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) P_i acts as a shuttle molecule to move energy from ATP to ADP.

• A. Energy from food sources can be used directly for performing cellular work.
• B. ADP + P_i 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. P_i 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 basically when the 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 an exergonic reaction, and it releases energy into the environment. ATP hydrolysis is usually 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 over here, we're showing you this pizza, and that's because a lot of the energy that we get is from the foods that we end up eating. When we eat pizza, it has various kinds of molecules including carbohydrates, proteins, and lipids. These molecules in the foods we eat provide energy for our bodies. Our bodies perform exergonic reactions to essentially break down the foods, starting with large food molecules and breaking them into smaller components, ultimately converting the energy in food into chemical energy in the form of ATP. This energy is used to make ATP. Once ATP is made, the cell can perform ATP hydrolysis. In this box, you can see the reactants needed for ATP hydrolysis to occur, which are ATP and water. ATP hydrolysis is an exergonic reaction that releases a lot of energy, creating a phosphate group as well as ADP. This released energy is crucial and is where energy coupling comes into play. ATP hydrolysis provides the energy input needed for an endergonic reaction, like using smaller molecules to build larger ones, and using the energy from ATP to create kinetic energy, such as when riding a bicycle. The movements and kinetic energy needed to ride a bike are derived directly from ATP hydrolysis, which uses energy from the foods we eat. Therefore, the foods we eat can ultimately be traced to providing the energy for our movements and muscle contractions. Exergonic reactions are used to power endergonic reactions, and this is the concept of energy coupling. This 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. 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.

• 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 in order to provide energy. Phosphorylation by ATP hydrolysis can actually have a wide variety of effects. Some of those effects include activating a target molecule so that it's capable of reacting, as well as changing the conformation of a target protein. Notice in the image on the left-hand side, we're showing a glucose molecule here as the green hexagon, and this glucose molecule is shown in its inactive form, so it's not able to react in this form. However, after ATP hydrolysis and phosphorylation of the glucose molecule, adenosine triphosphate, ATP, which has three phosphates, transfers the third phosphate to glucose. This phosphorylated form of glucose is actually the active form and would be able to go on to react.

Phosphorylation does not always lead to the activation of a target molecule. This is just an example of what phosphorylation can lead to, as it can have a wide variety of effects. In some scenarios, phosphorylation 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. On the right-hand side, we focus on a protein represented by a red circle. 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. 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 adenosine (a combination of adenine and a pentose sugar) and three phosphate groups. ATP is often referred to as the energy currency of the cell because it stores and provides energy for various cellular processes. When ATP is hydrolyzed, it releases energy by converting to ADP (adenosine diphosphate) and a free phosphate group. This released energy is used to power endergonic reactions, such as muscle contractions, active transport, and biosynthesis, making ATP essential for maintaining cellular functions and overall metabolism.

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 can be represented as:

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

The energy released during this reaction is used to drive various cellular processes, making ATP hydrolysis a key mechanism for energy transfer within cells.

What is energy coupling and how does it relate to ATP?

Energy coupling is the process where the energy released from an exergonic reaction, such as ATP hydrolysis, is used to drive an endergonic reaction that requires energy input. In cells, ATP hydrolysis is a common exergonic reaction that releases energy, which is then used to power endergonic reactions like muscle contractions, active transport, and biosynthesis. For example, the energy released from ATP hydrolysis can be used to convert smaller molecules into larger ones or to perform mechanical work, such as moving cellular structures. This coupling of reactions ensures that energy is efficiently transferred and utilized within the cell, maintaining cellular functions and metabolism.

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 alter the target molecule, influencing its function. For instance, phosphorylation can activate enzymes, making them capable of catalyzing reactions, or it can change the conformation of proteins, thereby altering their activity or interactions. The general reaction for phosphorylation can be represented as:

${\mathrm{ATP}}_{}+\mathrm{target}\to {\mathrm{ADP}}_{}+\mathrm{target}-P_i$

Phosphorylation is crucial for regulating cellular activities, as it can turn enzymes on or off, alter protein functions, and facilitate signal transduction pathways.

What are the components of an ATP molecule?

An ATP (adenosine triphosphate) molecule consists of three main components: adenosine and three phosphate groups. Adenosine itself is made up of two parts: a pentose sugar (ribose) and an adenine nitrogenous base. The three phosphate groups are linked in a chain, and the bonds between these phosphate groups store a significant amount of energy. The structure of ATP can be summarized as:

$\mathrm{adenosine}-P_1-P_2-P_3$

When ATP is hydrolyzed, it releases energy by breaking the bond between the second and third phosphate groups, converting ATP to ADP (adenosine diphosphate) and an inorganic phosphate (Pi).