Question about energy stored within chemcials. The body stores energy in the form of ATP. If energy . . .?

Question

is stored within ATP, doesn't this mean that ATP contains more energy than ADP contains. If yes, then doesn't the body in fact have to spend energy to form a molecule of ATP. And hence doesn't the body waste energy forming ATP? How much energy must the body spend to form a molecule of ATP. I suppose if the amount of energy necessary to form a molecule of ATP is small, then it is a minor price to pay for the convenience of effective energy storage.

I guess in a nutshell my question is . . .does the body have to exert energy to form a molecule of ATP? If so, must the body spend a significant amount to do so?

Answer 1

The amount of energy in ATP is NOT small. And yes, your body does have to put the energy in to get it out. But there's a good reason why it does so.

Think of it this way: Your car runs on gasoline, and that's pretty much it. But in the world, there are lots and lots of things that have energy. If you have the right equipment, you can use those other energy sources to MAKE gasoline.

So it goes with your cells. When your cells need energy, most of the time what they use is ATP. Unlike your car, you can't even really get much ATP from food - the reason ATP stores energy is because it doesn't LIKE being ATP... it quickly turns into something else (which is also why your body's long-term storage for energy is fat, not ATP). Instead, your body gets all of the hundreds of different things that it can use for energy and turns them all into ATP (or fat).

These different energy sources for your cells are all chemically very different and show lots of variation in the environment. If different things in your body needed different kinds of energy, then you'd have to work really hard to make sure you ate a hundred different things. But since everything is converted into one kind of 'energy currency', it doesn't create a huge difference in your body's operation if you eat a steak for one meal and a bag of chips for the next.

So yes. It takes energy to make ATP... even more than you get when you break it apart. But it's still a VERY good idea!

Answer 2

The energy in ATP is stored in the high energy bond by which the third phosphate is bound to ADP. However, the formation of ATP does not directly require energy. The further break down of glucose (from simple glycolysis in the cytoplasm) generates electrons (from the Krebs cycle, which occurs in mitochondria). There is a structure called ATP synthase in the membrane. When enough of a difference in charge (because there are more electrons in the mitochondrion than in the cytoplasm) occurs, the protons move through the ATP synthase, and this produces ATP. Essentially, the synthase harnesses the energy from allowing the protons to move down their concentration gradient to make ATP. There is more information on ATP synthast at this web site: http://www.sp.uconn.edu/~terry/images/anim/ATPmito.html. Actually, a scientist named Paul Boyer won the Nobel Prize in 1997 for his work on this.

Answer 3

Cells use the catabolism of compounds (i.e. glucose, fatty acids, amino acids, etc.) to synthesize ATP molecules. The most efficient source of energy is the Kreb's (a.k.a. TCA, Citric Acid) cycle and electron transport chain. The cycle takes high energy electrons from large compounds (after they are broken down into Acetyl CoA) and transfers the electrons to carriers NAD and FAD. The electron transport chain transfers those electrons through a series of steps and eventually onto oxygen to make water.
Long story short, the energy of those electrons is eventually contained in the phosphate bond of ATP. Don't think of it as making a new high energy bond. Think of it as transferring the energy of catabolism (of glucose, fat, etc.) into one usable, universal form. It's not that the body is "spending energy," it's converting it into a usable form. Hope that helps.

Answer 4

yes living systems must expend energy in order to phosphorilate ADP to ATP (attach another phosphate).

The energy efficiency of the entire process is around 62%. That's the free energy (deltaG) of complete oxidation of acetic acid, 805 kJ/mole and 50 kJ/mole for the complete hydrolysis of each ATP (under cellular conditions of course) of which 10 are produced per mole of acetic acid.

Compared to mechanical systems that's incredibly efficient.
To answer your question as to 'why,' you hit on it in your question. ATP is a very convenient form of energy storage. It can drive nearly all of your body's chemistry, both processes that are chemically non-spontaneous and those that are too slow without enzymes. Even at 62% conversion efficiency (which again is incredibly efficient) that 38% loss in free energy is still a small price to pay for the convenience.

Answer 5

Briefly I think that ATP has the virtue over ADP of being a convenient means of transfer of energy thru the body to where it is needed. It is a means of tranfer for energy. I could not find if energy is expended in converting ADP to ATP. Apparently it is inconsequential to the essential role ATP plays in every living thing.

From Wikipedia:
ATP is generated in the cell by energy-releasing processes and is broken down by energy-consuming processes, in this way ATP transfers energy between spatially-separate metabolic reactions. ATP is the main energy source for the majority of cellular functions. This includes the synthesis of macromolecules, including DNA, RNA, and proteins. ATP also plays a critical role in the transport of macromolecules across cell membranes, e.g. exocytosis and endocytosis.

Adenosine diphosphate, abbreviated ADP, is a nucleotide. It is an ester of pyrophosphoric acid with the nucleotide adenine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine.

ADP is the product of ATP dephosphorylation by ATPases. ADP is converted back to ATP by ATP synthases. ATP is an important energy transfer molecule in cells.

The total quantity of ATP in the human body is about 0.1 mole. The majority of ATP is not usually synthesised de novo, but is generated from ADP by the aforementioned processes. Thus, at any given time, the total amount of ATP + ADP remains fairly constant.

The energy used by human cells requires the hydrolysis of 100 to 150 moles of ATP daily which is around 50 to 75 kg. Typically, a human will use up their body weight of ATP over the course of the day.[18] This means that each ATP molecule is recycled 1000 to 1500 times during a single day (100 / 0.1 = 1000). ATP cannot be stored, hence its consumption being followed closely by its synthesis.



ATP is critically involved in maintaining cell structure by facilitating assembly and disassembly of elements of the cytoskeleton. In a related process, ATP is required for the shortening of actin and myosin filament crossbridges required for muscle contraction. This latter process is one of the main energy requirements of animals and is essential for locomotion and respiration.