A Wonder of the Biological World –
The Molecular Motor “ATP Synthase”
Get prepared to encounter one of the most powerful and obvious instances of intelligent design in the universe: the ATP Synthase. The ATP synthase is one of the wonders of the molecular world, and is the smallest molecular machine that we know of. It is the epitome of complex nano-technological design and engineering. Basically, the ATP synthase is an enzyme, a molecular motor, an ion pump, and another molecular motor all wrapped together in one amazing nano-scale machine. It plays an indispensable role in our cells, building most of the ATP that powers our cellular processes. The mechanism by which it performs this task is a real surprise.
ATP synthesis is composed of two rotary motors, each powered by a different fuel. The motor at the top, termed F0, an electric motor. It is embedded in a membrane (shown schematically as a gray stripe here), and is powered by the flow of hydrogen ions across the membrane. As the protons flow through the motor, they turn a circular rotor (shown in blue). This rotor is connected to the second motor, termed F1. The F1 motor is a chemical motor, powered by ATP. The two motors are connected together by a stator, shown on the right, so that when F0 turns, F1 turns too.
Motor to GeneratorSo why have two motors connected together? The trick is that one motor can force the other motor to turn, and in this way, change the motor into a generator. This is what happens in our cells: the F0 motor uses the power from a proton gradient to force the F1 motor to generate ATP. In our cells, food is broken down and used to pump hydrogen ions across the mitochondrial membrane. The F0 portion of ATP synthase allows these ions to flow back, turning the rotor in the process. As the rotor turns, it turns the axle and the F1 motor becomes a generator, creating ATP as it turns.
This enzyme is the primary source of ATP in a vast majority of living species on Earth, including us. In human body it daily generates over 50 kg of ATP, which is subsequently used to provide energy for various biochemical reactions, including DNA and protein synthesis, muscle contraction, transport of nutrients and neural activity, to name just a few.
In plants and photosynthetic bacteria ATP synthase is essential for solar energy conversion and carbon fixation. This is one of the oldest enzymes on Earth, which appeared earlier then photosynthetic or respiratory enzyme machinery.
ATP synthase is a huge molecular complex (>500,000 daltons) embedded in the inner membrane of mitochondria. Its function is to convert the energy of protons (H+) moving down their concentration gradient into the synthesis of ATP. 3 to 4 protons moving through this machine is enough to convert a molecule of ADP and Pi (inorganic phosphate) into a molecule of ATP. One ATP synthase complex can generate >100 molecules of ATP each second.
ATP synthase can be separated into 2 parts:
- Fo - the portion embedded in the inner mitochondrial membrane and
- F1-ATPase — the portion projecting into the matrix of the mitochondrion.
In both these cases, the machine is converting chemical energy into mechanical energy — the turning of the motor.
- from the hydrolysis of ATP in the in vitro case and
- the flow of protons down their concentration gradient in the intact mitochondrion
During ATP synthesis, the central rotor turns in the direction shown about 150 times every second. In order to provide energy to sustain our lives, every day, each one us produces a quantity of ATP by this mechanism that is approximately equal to our body weights.
ATP synthase is a key enzyme in energy transformation of a living cell.
The enzyme makes adenosine triphosphate (ATP) from adenosine diiphosphate (ADP) and inorganic phosphate (Pi).
ATP is a universal "energy currency" of a living cell and is essential for DNA synthesis, muscle contraction, ion and nutrients transport, signal transduction, etc.
The amazing feature of ATP synthase is rotary catalysis: a complex of subunits rotates relative to the rest of the enzyme and the mechanical energy of rotation is driving ATP synthesis reaction.
In turn, the rotation is powered by transport of protons trough the membrane segment of ATP synthase. The driving force for this transport is the electrochemical potential difference of proton across the membrane.
ATP synthase is therefore the smallest know mechano-electro-chemical energy transducer in the world, that works as a nano-turbine.
Ask yourself this: Is it logical to think such an amazingly complex nano-technological wonder could ever come about by chance? Is it possible for any machine to arise by random chance processes?
Or is Intelligent Design a more plausible scientific explanation?
- Pastor J.