<< Chapter < Page Chapter >> Page >
This illustration shows the molecular structure of NAD^{+} and NADH. Both compounds are composed of an adenine nucleotide and a nicotinamide nucleotide, which bond together to form a dinucleotide. The nicotinamide nucleotide is at the 5' end, and the adenine nucleotide is at the 3’ end. Nicotinamide is a nitrogenous base, meaning it has nitrogen in a six-membered carbon ring. In NADH, one extra hydrogen is associated with this ring, which is not found in NAD^{+}.
The oxidized form of the electron carrier (NAD + ) is shown on the left and the reduced form (NADH) is shown on the right. The nitrogenous base in NADH has one more hydrogen ion and two more electrons than in NAD + .

Atp in living systems

A living cell cannot store significant amounts of free energy. Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion that could damage and then destroy the cell. Rather, a cell must be able to handle that energy in a way that enables the cell to store energy safely and release it for use only as needed. Living cells accomplish this by using the compound adenosine triphosphate (ATP). ATP is often called the “energy currency” of the cell, and, like currency, this versatile compound can be used to fill any energy need of the cell. How? It functions similarly to a rechargeable battery.

When ATP is broken down, usually by the removal of its terminal phosphate group, energy is released. The energy is used to do work by the cell, usually by the released phosphate binding to another molecule, activating it. For example, in the mechanical work of muscle contraction, ATP supplies the energy to move the contractile muscle proteins. Recall the active transport work of the sodium-potassium pump in cell membranes. ATP alters the structure of the integral protein that functions as the pump, changing its affinity for sodium and potassium. In this way, the cell performs work, pumping ions against their electrochemical gradients.

Atp structure and function

At the heart of ATP is a molecule of adenosine monophosphate (AMP), which is composed of an adenine molecule bonded to a ribose molecule and to a single phosphate group ( [link] ). Ribose is a five-carbon sugar found in RNA, and AMP is one of the nucleotides in RNA. The addition of a second phosphate group to this core molecule results in the formation of adenosine di phosphate (ADP); the addition of a third phosphate group forms adenosine tri phosphate (ATP).

This illustration shows the molecular structure of ATP. This molecule is an adenine nucleotide with a string of three phosphate groups attached to it. The phosphate groups are named alpha, beta, and gamma in order of increasing distance from the ribose sugar to which they are attached.
ATP (adenosine triphosphate) has three phosphate groups that can be removed by hydrolysis to form ADP (adenosine diphosphate) or AMP (adenosine monophosphate).The negative charges on the phosphate group naturally repel each other, requiring energy to bond them together and releasing energy when these bonds are broken.

The addition of a phosphate group to a molecule requires energy. Phosphate groups are negatively charged and thus repel one another when they are arranged in series, as they are in ADP and ATP. This repulsion makes the ADP and ATP molecules inherently unstable. The release of one or two phosphate groups from ATP, a process called dephosphorylation    , releases energy.

Energy from atp

Hydrolysis is the process of breaking complex macromolecules apart. During hydrolysis, water is split, or lysed, and the resulting hydrogen atom (H + ) and a hydroxyl group (OH - ) are added to the larger molecule. The hydrolysis of ATP produces ADP, together with an inorganic phosphate ion (P i ), and the release of free energy. To carry out life processes, ATP is continuously broken down into ADP, and like a rechargeable battery, ADP is continuously regenerated into ATP by the reattachment of a third phosphate group. Water, which was broken down into its hydrogen atom and hydroxyl group during ATP hydrolysis, is regenerated when a third phosphate is added to the ADP molecule, reforming ATP.

Questions & Answers

big bang theory was discovered by
Sweety Reply
the meaning of nucleus
Spring Reply
nucleus Is also known as the cell's headquarters
what is pathology?
Azi Reply
is the study of diseases, it's cause and development of a disease
State the law of segregation
Theolla Reply
what is a cell
Bunmi Reply
A cell is a basic structural unit of an organism
what are molecules?
comapare and contrast food chain
Chengo Reply
what are the classes of biology
Oluebube Reply
Microbiology Biochemistry Botany Zoology Horticulture
what is translocation
James Reply
what is hominids
Dauba Reply
what is genetics
Musa Reply
what is meiosis?
list three vertebrate animal and three invertebrate animal
Katie Reply
lizard, goat, frog ,earthworm, housefly, tapeworm
what is meant by radial symmetry?
what is meaning of polysaccharide
mark Reply
this is the combination of two or more monosacharide
long chain of monosacchrides joined together by glycosidic bonds
water as a function in cell for inorganic substances
chisom Reply
hi john....wat about for mineral salts, its function in a cell and structure
hi chisom which topic is this
what is sepsis
this biology is for which grade?
Janet Reply
state any one specialized animal cell and it's function
Pascal Reply
sperm cell: Fertilization

Get the best Biology course in your pocket!

Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?