SONGLyrical DNA
Energy In, Order Stays
A song about why living things need a constant input of energy. The lyrics run from the first and second laws of thermodynamics and how a cell keeps its order without breaking them, through energy input outpacing energy loss and coupling reactions that release energy to ones that require it, to pathways that hand energy along one controlled step at a time, and what happens when the flow stops. Select any highlighted line to see the biology behind it.
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Interactive lyrics
Lines with a dotted underline and a + marker have an explanation. Select one and the science appears beside the lyrics. Everything else is ordinary lyric text.
Intro
Vai, vai, vai!
Energy in!
Vai, vai, vai!
Energy in!
Energy through!
Input high!
Loss controlled!
Bring in the power
To maintain the whole!
Beat Drop
Energy in!
Order stays!
Energy in, order stays!
Power the cell, run the pathways!
Energy in, don't let it fade!
Energy in, order stays!
Build, repair, transport, change!
Keep that flow from night to day!
Energy in, order stays!
Verse 1
Energy enters, cells can use it
Life maintains its inner order
By taking energy repeatedly
That is how the system stays
Pre-Drop
Input greater than the loss!
Keep the structure, pay the cost!
Energy low, processes slow!
Energy gone, the whole thing goes!
Drop
Energy in, order stays!
Energy in, order stays!
Power the cell, run the pathways!
Energy in, don't let it fade!
More coming in than the energy drained!
Energy in, order stays!
Build, repair, transport, change!
Keep that flow from night to day!
Energy in, order stays!
Verse 2
Energy out from one process
Drives another that requires it
Release and require, side by side
One supplies the energy for the other to rise
Move a molecule
Build a chain
Repair a structure
Maintain a gradient
Energy released?
Connect it!
Energy required?
Direct it!
One reaction pays the fee
For another
Cellular activity!
Break
Release!
Require!
Couple the fire!
Release!
Require!
Take it higher!
Verse 3
Step two makes another product
Send it down the line
Step one!
Step two!
Step three!
Go, go!
Product becomes reactant
Keep the pathway in flow!
Step four!
Step five!
Keep it controlled!
Every small reaction
Helps maintain the whole!
Build
Energy drops
Order falls
Without energy flow
Life cannot prevail
Final Drop
Energy in, order stays!
Energy in, order stays!
Energy, energy in, order stays!
Power the cell!
Run the pathways!
Input higher than the loss!
Keep the system, pay the cost!
Energy in, energy in, order stays!
Couple reactions, transfer the change!
Step by step, control the flow!
Product forward, next step, go!
Energy in!
Energy through!
Every living system
Needs energy to do!
Energy in!
Do not delay!
Significant loss
Means life fades away!
Outro
Input!
Transfer!
Couple!
Control!
Step by step
To maintain the whole!
Energy in, order stays!
Energy in, order stays!
Concepts covered
Energy input for all lifeEvery organism, from a single bacterium to a tree or a whale, depends on an input of energy from outside itself, whether used right away or stored for later. The source differs. Plants, algae and some bacteria capture light energy. Some bacteria and archaea draw energy from inorganic chemicals such as hydrogen sulfide. Animals, fungi and many microbes take in energy stored in the organic molecules of their food, and that food traces back to organisms that captured light or chemical energy.
Energy input exceeding lossSome of the energy an organism takes in is lost without doing any work, locked in wastes or given off as heat. Input must exceed that loss, or nothing is left to power cellular processes, including the work of staying organized, which also ends up as heat. Only intake beyond all of this can go to growth, reproduction and storage, such as new cells, fat or starch. When intake falls short, those reserves are drawn down.
Order in a living cellOrder in a cell means its parts are arranged in specific, unlikely ways: DNA and proteins built with exact sequences of subunits, membranes that hold particular molecules inside, and compartments with different contents. Left alone, such arrangements drift toward more probable, mixed-up states. Large molecules slowly break apart by reacting with water, damage builds up, and substances leak across membranes and spread out evenly. Holding that arrangement takes continuous upkeep.
First law of thermodynamicsThe first law of thermodynamics says energy can be transferred and transformed but is never created or destroyed. A cell therefore cannot make energy; it can only convert energy it takes in. In a leaf, light energy becomes chemical energy stored in sugar. In a muscle, chemical energy from food becomes the motion of protein fibers, and some becomes heat. Chemical energy is potential energy held in how atoms are arranged, released when molecules are rearranged into more stable ones.
Second law of thermodynamics and heatNo energy conversion in a cell is perfectly efficient. The second law of thermodynamics says every energy transfer increases the disorder of the universe, and in living things some energy is always released as heat. That heat cannot be turned back into cellular work, because a cell is at nearly one temperature throughout and work can be drawn from heat only across a temperature difference. Unlike matter, which can be recycled, energy therefore moves through living systems in one direction.
Organisms as open systemsGrowing and building make a cell more ordered, which can seem to break the second law. It does not, because organisms are open systems that exchange energy and matter with their surroundings. A cell captures light, or takes in energy-rich material such as sugar and breaks it into simpler molecules, and either way it gives off heat. The disorder added outside is greater than the order gained inside, so the total disorder of cell plus surroundings still rises.
Coupling through a shared stepFor energy to pass from one reaction to another, the two must share a step: a molecule or a protein that both act on. Often ATP hands one of its phosphate groups to a reactant or to a protein, and the phosphorylated molecule is now reactive enough, or reshaped enough, to carry out the energy-requiring change. Taken together, the paired reactions release energy overall, so the pair can proceed. ATP is the most common link, but not the only one.
ATP as a short-term carrierBreaking down fuel such as glucose or fat captures part of its energy by attaching a phosphate group to ADP, forming ATP. ATP is a quick-turnover carrier, not a reserve. Each molecule is usually spent soon after it is made, giving up a phosphate and returning to ADP. A cell holds only a small amount of ATP at any moment, so it must regenerate it nonstop. The same ADP is recharged with phosphate again and again rather than built from scratch.
Pathway intermediates as junctionsSince each step's product is typically the next step's reactant, a pathway is a chain of separate molecules, and other pathways can branch off from it. Some intermediates are drawn off as raw material: those of glycolysis and the Krebs (citric acid) cycle supply starting points for making certain amino acids and fats. Traffic also runs the other way, as fats and proteins are broken into pieces that join the same pathways partway along. The chain becomes a hub that links much of metabolism.
Enzyme control of key stepsEach step has its own enzyme, but cells concentrate regulation at a few of them, often one at an early step that commits material to the pathway. Making more or less of that enzyme, or switching its activity up or down, speeds or slows the whole pathway to match demand. In feedback inhibition, a product of the pathway binds an enzyme near the start and slows it. High levels of ATP, for instance, slow an early step of glycolysis.
Small steps versus one burstBurning sugar in a flame and breaking it down completely in a cell release the same total energy, since both end with carbon dioxide and water. The difference is where it goes. A flame releases it all at once as heat and light, in a form no cell could capture. A cell takes the molecule apart in many small reactions, and much of the energy released along the way is transferred into carriers such as NADH and ATP. Some still escapes as heat, but a sizable share is captured for cellular work.
Cell breakdown after energy lossInside a cell that loses its energy supply, such as a heart or brain cell after a blocked artery cuts off oxygen, failures follow one another. ATP runs low, so membrane pumps slow and stop. Ions flow back down their concentration differences, water follows them in, and the cell swells. Repair and replacement of damaged parts halt at the same time. If oxygen returns quickly, many cells recover. If it does not, membranes rupture, the contents spill into the surrounding tissue, and the cell dies.
