Coupled Reactions

Summary

In this podcast, Mr. Andersen explains the concept of coupled reactions, which are essential in biology. He uses the analogy of a water wheel to describe how energy from one reaction powers another. The podcast covers the breakdown and recharge of ATP, the role of coupled reactions in processes like photosynthesis, cellular respiration, and muscle movement. Andersen also touches on redox reactions, explaining electron transfer using the mnemonic 'Oil Rig.' He emphasizes how exergonic reactions release energy, while endergonic reactions consume it, linking thermodynamics to biological processes.

Takeaways

• 🔗 Coupled reactions in biology are analogous to water wheels, where one process powers another.
• 🌊 ATP is the energy currency in cells, acting like a rechargeable battery, with its breakdown releasing energy for other reactions.
• 🌱 Photosynthesis involves coupled reactions, such as the light reactions where electron movement powers proton pumping.
• 🔋 The Calvin cycle also features coupled reactions, using the energy from ATP to fuel the synthesis of G3P.
• 🚀 Cellular respiration is a series of coupled reactions, breaking down glucose and storing energy in NADH/NADPH.
• ⚡ Oxidative phosphorylation is a coupled reaction where electron flow drives proton pumping to generate ATP.
• 💪 Muscle movement, like raising a thumb, is powered by coupled reactions involving ATP breakdown and myosin movement along actin.
• 🔁 Redox reactions are a type of coupled reaction where electrons are transferred from one molecule to another, releasing energy.
• 🔄 The sodium-potassium pump in nerve cells is an example of a coupled reaction that maintains a gradient for nerve function.
• 🔄 Redox reactions can occur in various substances, not just sugars, such as in the burning of methane, propane, or gasoline.

Q & A

What is a coupled reaction in biology?

A coupled reaction in biology is when the energy released from an exergonic (energy-releasing) reaction is used to drive an endergonic (energy-consuming) reaction. This coupling allows processes that require energy to occur by using the energy from reactions that release it.

What analogy is used in the podcast to explain coupled reactions?

The analogy of a water wheel (or water mill) is used. As water flows down, it powers a wheel which is attached to a stone that grinds grain into flour. In biology, chemicals are used instead of water to couple reactions.

How is ATP related to coupled reactions?

ATP (adenosine triphosphate) plays a crucial role in coupled reactions. It stores energy in its phosphate bonds, and when the third phosphate group is broken off, it releases energy (with a delta G of -7.3 kcal/mol), which can be used to power other reactions.

What happens after the third phosphate group is broken off from ATP?

After the third phosphate group is broken off, ATP becomes ADP (adenosine diphosphate). The phosphate can be reattached in a process similar to recharging a battery, allowing the cycle to repeat throughout the day.

Can you provide an example of a coupled reaction in photosynthesis?

One example of a coupled reaction in photosynthesis occurs in the light reaction. The energy from a flowing electron is used to pump protons into the thylakoid membrane, coupling the movement of electrons with the movement of protons.

What role do coupled reactions play in the Calvin cycle?

In the Calvin cycle, ATP is broken down into ADP, and this reaction is coupled with the creation of G3P (glyceraldehyde-3-phosphate), a molecule important for sugar synthesis. Another coupled reaction in the Calvin cycle is the breakdown of NADPH into NADP+.

What is the connection between coupled reactions and cellular respiration?

In cellular respiration, coupled reactions occur when glucose is broken down into pyruvate through glycolysis, which is coupled with the storage of energy in NADH. Similar coupling happens in the Krebs cycle and oxidative phosphorylation.

How do coupled reactions function in the sodium-potassium pump?

The sodium-potassium pump in nerve cells uses coupled reactions to establish a gradient. This gradient is essential for transmitting nerve signals, and it is a key part of how energy is transferred in the nervous system.

What is a redox reaction, and how is it related to coupled reactions?

A redox reaction involves the transfer of electrons between molecules. It can be seen as a coupled reaction within a single process, where one molecule loses electrons (oxidation) and another gains them (reduction). This transfer of energy is vital in processes like cellular respiration.

What does the mnemonic 'OIL RIG' stand for in redox reactions?

The mnemonic 'OIL RIG' stands for 'Oxidation Is Losing' (electrons) and 'Reduction Is Gaining' (electrons). It helps remember the direction of electron transfer in redox reactions, such as the transfer from sugar to oxygen in cellular respiration.

Outlines

00:00

🌱 Understanding Coupled Reactions in Biology

Mr. Andersen introduces coupled reactions by comparing them to a water wheel, where the flow of water powers a wheel to grind grain into flour. In biology, chemical reactions are coupled, with ATP breakdown being a prime example. ATP, or adenosine triphosphate, releases energy when a phosphate group is removed, and this energy is used to power other reactions. The analogy is extended to explain how energy from the sun is transferred to the human body, specifically to the thumb, through a series of coupled reactions starting with photosynthesis in plants. The light reactions in photosynthesis involve the movement of electrons and protons, which are coupled to produce ATP and NADPH. The Calvin cycle also involves coupled reactions, where ATP is broken down to power the synthesis of G3P. Cellular respiration is another process where coupled reactions occur, such as glycolysis, where glucose is broken down into pyruvate, and the energy is stored in NADH. The process continues with the Krebs cycle and oxidative phosphorylation, where electrons are transferred, and protons are pumped to produce more ATP. The concept of coupled reactions is essential for understanding how energy is transferred and utilized in biological systems.

05:02

🔋 The Role of Redox Reactions in Energy Transfer

The second paragraph delves into redox reactions, which are a type of coupled reaction where electrons are transferred from one chemical species to another. Mr. Andersen explains that during cellular respiration, electrons are transferred from sugar to oxygen, releasing energy that is used to produce ATP. The process is compared to burning oil or methane, where the loss of electrons results in the release of energy as heat. To help remember the concepts of oxidation and reduction, Mr. Andersen suggests the mnemonic 'Oil Rig,' where oxidation is the loss of electrons (as in the sugar), and reduction is the gain of electrons (by oxygen). The paragraph emphasizes the importance of understanding thermodynamics, particularly the concepts of exergonic (energy-releasing) and endergonic (energy-consuming) reactions, to grasp how coupled reactions function in biological systems.

Keywords

💡Coupled Reactions

Coupled reactions involve two chemical reactions where one releases energy and the other consumes it. The video uses the analogy of a water mill, where flowing water powers the grinding of grain, to explain how energy from one process powers another. In biology, this happens when the energy from ATP breakdown is used to fuel other reactions.

💡ATP (Adenosine Triphosphate)

ATP is the primary energy carrier in cells. It stores energy in its high-energy phosphate bonds and releases it when the third phosphate group is removed, converting ATP to ADP. In the video, ATP is described as a rechargeable battery that constantly cycles through energy release and storage, driving numerous biological processes.

💡Exergonic Reaction

An exergonic reaction is a chemical reaction that releases energy. In the video, breaking down ATP into ADP is an example of an exergonic reaction, which releases energy that can be used to power other biological functions.

💡Endergonic Reaction

An endergonic reaction requires energy input to proceed. The video mentions that such reactions are often coupled with exergonic reactions. For example, the formation of glucose during photosynthesis requires energy, which is provided by the light reactions.

💡Photosynthesis

Photosynthesis is the process by which plants convert light energy into chemical energy. In the video, the light reactions in photosynthesis are described as using the energy from electrons to pump protons and generate ATP, an example of a coupled reaction in nature.

💡Cellular Respiration

Cellular respiration is the process where cells convert glucose into usable energy (ATP). The video illustrates how the breakdown of glucose into pyruvate during glycolysis is coupled with the storage of energy in molecules like NADH, showcasing multiple coupled reactions.

💡Redox Reaction

A redox reaction involves the transfer of electrons from one molecule to another. In the video, redox reactions are highlighted in cellular respiration, where electrons from glucose are transferred to oxygen, generating water and releasing energy to form ATP.

💡NADH

NADH is a coenzyme that carries electrons during cellular respiration. In the video, it is produced during glycolysis and the Kreb cycle, storing energy that will later be used in oxidative phosphorylation to generate ATP.

💡Sodium-Potassium Pump

The sodium-potassium pump is a transport protein in cell membranes that uses energy to move sodium ions out and potassium ions into cells, maintaining a crucial electrochemical gradient. In the video, this process is described as a coupled reaction that is essential for nerve function, including making the thumb move.

💡Oxidative Phosphorylation

Oxidative phosphorylation is the final stage of cellular respiration, where the energy from electrons is used to produce ATP. The video describes how the flow of electrons and the pumping of protons across the mitochondrial membrane drive the formation of ATP through the enzyme ATP synthase, a major coupled reaction in energy production.

Highlights

Coupled reactions are important in biology but hard to define.

An analogy of a water wheel is used to explain coupled reactions.

In biology, chemical reactions are coupled instead of using water like in water wheels.

ATP breakdown is a key chemical reaction in biology with a delta G of negative 7.3 kilocals per mole.

ATP can be thought of as a rechargeable battery within living organisms.

The body goes through its weight in ATP every day.

Coupled reactions are familiar but the term might not be.

Energy transfer from the sun to the thumb involves multiple coupled reactions.

Photosynthesis involves coupled reactions in the light reaction.

The Calvin cycle also involves coupled reactions.

Cellular respiration includes coupled reactions in glycolysis and the Kreb cycle.

Oxidative phosphorylation is a coupled reaction involving electron flow and proton pumping.

The sodium potassium pump in nerves is an example of a coupled reaction.

Muscle movement, like raising a thumb, is powered by coupled reactions.

Coupled reactions couple exergonic (energy releasing) with endergonic (energy consuming) reactions.

Redox reactions involve the transfer of electrons and energy.

Redox reactions can be remembered by the acronym OIL RIG: oxidation is losing electrons, reduction is gaining.

Understanding coupled reactions requires a basic understanding of thermodynamics.

Transcripts

Hi. It's Mr. Andersen. And in this podcast I'm going to talk about coupled reactions.

Coupled reactions are really important in biology. But it's hard to find a good definition

for what a coupled reaction is. And so whenever I'm failed for a definition I go to an analogy.

And so let's talk about this which is a water wheel or a water mill. Basically what happens

is as the water flows down it's going to power this giant wheel. And inside here that wheel

is going to be attached to a stone. And it's going to be used to grind grain into something

like flour. A windmill works the same way. And so basically what we're doing is we're

coupling the power of that flowing river with the power of this grinding of the mill. And

so in biology we don't use water. We use chemicals. And so the big chemical reaction that you

should be familiar with is the breakdown of ATP. So this is adenosine triphosphate. It's

triphosphate because you have three phosphate groups here on the end. And so basically it

has a delta G of negative 7.3 kilocals per mole. That means that it releases energy when

this third phosphate is broken off. And so if we look at what that looks like. Basically

this phosphate comes off. And we can use that to power other reactions. What happens next?

Well we have to reattach that phosphate. And so it's kind of like a rechargeable battery.

In fact this is the rechargeable battery inside life. And so we constantly are going from

adenosine triphosphate or ATP. We're releasing that phosphate to make ADP. And then we're

storing it again. Over and over and over again. And we do this constantly all day. And you

go through about a body's worth of weight in ATP everyday, which is a huge amount. And

so you're probably familiar with coupled reactions. But maybe not the term. And so what I'm going

to do is I'm going to from the sun to the thumb. In other words I'm going to show you

how energy is transferred from the sun to your thumb or the raising of your thumb. And

all of the coupled reactions that we see within that. And so we have to start of course with

plants. When we're talking about photosynthesis. The first part of photosynthesis is the light

reaction. Right here. We're inside the thylakoid membrane. And so as this electron moves through

here we're using the energy of that flowing electron to pump protons to the inside. So

we're coupling the reaction or that movement of the electron with the movement of the protons.

So that's a coupled reaction. Let me find another one. Right here we're moving this

electron here and we're eventually making NADPH. So that's a coupled reaction. Or right

here we're pumping those protons back through that thylakoid membrane and we're making ATP

out of it. And so that's a coupled reaction. We'd have another coupled reaction here. So

we have a number of coupled reactions. And we're still just in the light reaction. If

we look in the Calvin cycle you can see right here, basically we're breaking ATP down into

ADP. And we're using that to couple this reaction. Which is eventually going to make G3P. After

we have coupled another reaction. Breaking down NADPH into NADP+. And even if you look

back here as we make RUBP we're doing another coupled reaction. In this case we're taking

the energy that we'd stored in the light reaction. And we're actually releasing that to make

RUBP. So a bunch of coupled reactions. But we're not to the thumb yet. Because in the

thumb what we've got to do is we've got to take sugar and break it down. That's what

life does. And so basically we're talking now about cellular respiration. So where is

the coupled reaction here? As we break glucose down into pyruvate through the process of

glycolysis we're coupling that reaction with this other endergonic reaction where we're

storing that energy in NADPH. Or NADH, excuse me. Same thing here. As we breakdown and make

acetyl CoA we make more NADH. And we're doing the same thing in the Kreb cycle. Now if we

look at the oxidative phosphorylation, we're coupling the flow of these electrons with

the pumping of the protons. And we're coupling that reaction as the protons flow back in

with ATP synthase. And so what are you doing in a coupled reaction? You're releasing energy

in one reaction or one process. And then storing it in another. But let's keep going. We're

not to the thumb yet. In order to get your thumb to rise you have to actually use a nerve.

And to do that we're using another coupled reaction. This is the sodium potassium pump

in your nerves. And we're using that to establish a gradient. Or even if we get to the muscle

itself. As we breakdown that ATP into ADP, it's moving that myosin along the actin. And

that's actually what makes your muscle move and makes your thumb move up. And so what

are coupled reactions? Coupling the exergonic with the endergonic. The energy releasing

with the energy consuming reactions. But sometimes that occurs within an equation itself. And

so now we get to something that always confuses students. And these are called the redox reactions.

And so redox reactions are basically, in this case we're looking at electrons and where

the electrons flow. And so this right here is sugar with oxygen makes carbon dioxide

and water. And then it's going to make ATP. And so this is cellular respiration. And so

we call this a redox reaction because the electrons and the energy of those electrons

is being transferred from the sugar to the oxygen to make carbon dioxide. And the oxygen

is gaining those electrons. And as it's gaining those electrons it's eventually becoming water.

So we lose the electrons here. We gain the electrons here. So you can see it's like a

coupled reaction within a reaction. So we're losing electrons of the food. And we're gaining

the electrons of the oxygen. And when I say losing and gaining what I means is we are

physically transferring those electrons from one chemical to another. And they're high

energy electrons in our food. And then as they fall down to low energy bonded with oxygen

we release a lot of that energy. In this case in the form of ATP. But this doesn't have

to be sugar up here. This could be for example methane gas. What you burn in a bunsen burner.

And so as we lose those electrons in there we get energy in the form of heat. Or this

could be propane or gasoline or anything like that is a redox reaction. Losing electrons

and gaining electrons. Now that's sometimes confusing because we've got oxidation, reduction.

And so here's a quick way to remember that. The way I remember it is Oil Rig. And this

is what an oil rig looks like. And if you think about it the burning of oil is a redox

reaction. But why do I even talk about Oil Rig? Well if you remember O I L R I G. That

will remind you that oxidation is the the losing of electrons. In cellular respiration

that would be from our sugar. And reduction is gaining. In this case would be the gaining

of electrons by oxygen. And so that's just a coupling within a reaction. And so hopefully

that makes sense. What coupled reactions are. You just have to have a little bit of understanding

of thermodynamics. Exergonic and endergonic reactions. And I hope that's helpful.