Cellular Respiration
Energy Causes Movement
Without energy nothing moves.
Energy caused the formation of our planet.
Energy causes earthquakes. Energy causes Volcanoes and their gases to erupt, spewing Carbon Dioxide into the air.
Energy causes air to move. Energy causes carbon dioxide to move into leaves.
Energy causes the water cycle.
Energy causes carbon dioxide to combine with water to make glucose.
Energy causes you to move and to eat food. You eat food for energy (and atoms).
Energy causes your heart to beat.
Energy causes glucose to be turned back into carbon dioxide and water. Energy causes cells to be 'alive'.
Energy causes Proteins to Move.
Proteins need Energy to move.
Proteins moving is life.
Each protein that is made in your body needs energy to be made as it is made by Ribosomes.
Ribosomes are proteins that move.
Ribosomes are enzymes.
Enzymes are proteins that do stuff.
Doing stuff requires energy
You can only do stuff if you have energy.
Each protein needs energy to do each of the movements it must make to do the stuff that it does.
So to type, how many proteins are doing stuff and how many movements does it take to do that stuff and how does energy get to where it needs to for these movements to occur?
If we trace the source of energy for us and for all large life on earth, we find that the energy comes from the sun and is put into the systems of life through photosynthesis.
We saw that photosynthesis is powered by energy from the Sun.
We know that this energy moves through food chains.
But how does that energy get to your Proteins?
When compounds with lots of atoms are made from compounds that have few atoms, a lot of energy has to be put in. Some of that energy stays in the big compound.
In other words, it takes lots of energy to build complex compounds from simple compounds and some of that energy is stored in the complex compound as chemical potential energy.
When a big compound with lots of atoms is broken down into smaller compounds with fewer atoms, energy needs to be put in to start the reaction, but lots of energy is then released from the big compound
In other words, it takes some energy to start to deconstruct complex molecules into simple molecules, but that deconstruction releases lots of stored chemical potential energy
This is much like building a brick wall, and then pushing it over.
Building by hand takes lots of energy. Pushing it over takes some energy. When it crashes down and brakes back into bricks we hear that energy being released.
Photosynthesis makes the complex compound glucose from the simple compounds carbon dioxide and water.
To make glucose, energy from light is put in. Some of the energy put in is 'lost' as heat. Some remains within the compounds.
So glucose contains more chemical potential energy than water and carbon dioxide.
When we break that complex glucose back down to Carbon dioxide and water, the stored energy within the molecule is 'released'.
But how does this 'released' energy get to the millions of proteins working in each cell?
What if I told you, that you have millions of Tiny Batteries inside your cells.
What if I told you that it is these tiny batteries that take energy to proteins.
Solar energy, from the sun, is stored in glucose as Chemical Potential Energy.
This glucose is broken apart in your cells and turned back into carbon dioxide and water
As it is broken apart energy is released
This energy is used to recharge the batteries that power the thousands of protein actions occurring in a cell every second
Billions of protein actions within your body every second of every day
These batteries have two names, one when flat and one when recharged:
When fully charged they are Adenosine Triphosphate, ATP
When flat they are Adenosine Diphosphate, ADP
Adenosine Tri-Phosphate
The above two clips are here to show what ATP does inside a cell
ATP contains Adenine - the same as the Adenine or the A of ATCG found in DNA. Attached to the Adenine is a Ribose sugar, the same as the ribose from RNA.
Together: Adenine + Ribose = Adenosine
This Adenine + Ribose then has a phosphate attached to it. The same as the phosphate backbone of RNA.
This links back to the chemical evolution of life, with the same molecules doing different functions to continue the uninterrupted string of reactions that have been running for billions of years to maintain life on our planet
Adenosine Diphosphate contains 2 of these phosphate groups
Adenosine Diphosphate is a stable molecule.
Adenosine Diphosphate is the flat battery.
When glucose is broken, some of that energy escapes as heat - this keeps us warm
When glucose is broken, some of that energy is used to attach a third phosphate group to ADP.
This makes the molecule Adenosine Triphosphate, or ATP
This phosphate is only loosely held on and breaking it off requires very little activation energy, but it releases a large amount of energy
This energy, released right up against proteins, cause them to change shape (usually by the temporary attachment of the third phosphate to the protein.
After the protein changes shape, the phosphate might be released, causing the protein to change its shape back.
Respiration
The Release of Energy
We really do 'burn our food.
The chemical equation is the same
The only difference is that we are over 60% water
For fire, the energy is released as heat and light
For respiration, the energy is used to charge the ADP batteries, turning them into ATP
Some is also lost as heat and Infrared light
Plants use energy from the sun to make glucose
They then make more complex molecules by linking glucose together or by reconstructing the carbon atoms into other molecules such as lipids
A vegetable oil can have over 100 atoms. Sunflower oil has 55 Carbons, 98 Hydrogens and 6 Oxygens.
To make this molecule, the plant has to put in a lot of energy. This large complex molecule thus contains a lot more energy than glucose.
The muscle cells of a human will burn these fat molecules preferentially. It takes time for the cell to break down and burn fat, but it will get a lot of energy from it.
However, much like burning paper or burning a log, it is easier and faster to burn glucose.
The human body will convert big fat molecules into lots of smaller glucose molecules in the liver.
These smaller glucose molecules can be burnt in all cells, from muscle cells to brain cells.
This Burning inside of water filled cells is called Respiration
To burn the fuel, to burn glucose, the cells need oxygen
To have a good strong fire, you need oxygen
To burn the fuel, to burn glucose, the cells need oxygen
This graph compares the energy released from burning glucose in a fire and burning glucose through cellular respiration
Glucose in both cases has the same amount of energy to start with
The end products; Carbon Dioxide and water, both have far less energy than glucose
Notice that in the fire a large amount of activation energy is required to start the reaction of combining oxygen to the glucose to start making carbon dioxide and water. This is the heat required to burn sugar
Notice that in respiration there is lots of small activation energies - this is because the reaction is catalyzed by enzymes
All of the energy from glucose is released very quickly in the fire
The energy from glucose is slowly released in cellular respiration, allowing the energy to be 'captured' and used to put phosphates onto ADP to make ATP
Aerobic Respiration - 32 ATP
To attach a phosphate onto Adenosine Diphosphate to make Adenosine Triphosphate energy is required
During Cellular respiration, energy is slowly released from glucose.
This energy is used to attach Phosphates onto Adenosine Diphosphates
This process is step by step
At the end of it you will have attached 38 Phosphates onto 38 Adenosine Diphosphates to make 38 Adenosine Triphosphates
38 ATP
This process of creating 38 ATP from 38 ADP uses:
1 Glucose + 6 Oxygen molecules = 6 Carbon dioxide + 6 Water
It is the reverse of photosynthesis
The fact that these two systems are linked, make the chemical reactions of photosynthesis and cellular respiration sustainable. They can run in unison for billions of years.
Fueling living systems with solar Energy. Taking energy from the sun and releasing it within living cells
You make 38 ATP, but to power the enzymes involved in the process of aerobic respiration you use up 6 of them. So 6 ATP are turned back into ADP to overcome the activation energy of several of the steps.
So its a profit of only 32 ATP
Though some places say that the profit is 36 and others say that the profit is 34, current research indicates that the profit is 32 ATP
This process is called Aerobic Respiration because Oxygen is used.
Aerobic = Air
Aerobic Respiration:
1 Glucose + 6 Oxygen molecules = 6 Carbon dioxide + 6 Water
Anaerobic Respiration - 2ATP
Anaerobic means "without air"
More specifically it means without oxygen
Without oxygen only the first part of cellular respiration can occur. This first part is called glycolysis (the splitting of glucose)
Glycolysis requires an investment of energy to start the reaction, an investment of energy to overcome the activation energy requirement
So even through it creates 4 ATP in the image below, you will see that 2 ATP were used up. So the profit is only 2ATP
Anaerobic Respiration occurs in muscles when they are burning glucose faster than the body can get oxygen to them. This happens when you go for a sprint and is the limiting factor on how long you can sprint for
Everything that happens in the Mitochondria use oxygen
The splitting the 6 Carbon glucose into two 3 Carbon Pyruvate molecules yields enough energy to stick 2 Phosphates onto 2 ADPs to make 2 ATPs
If there is no oxygen, then this is the end of the process and no more ATP will be generated
An enzyme will turn this 3 Carbon Pyruvate into the 3 Carbon Lactate
1 Glucose = 2 Pyruvate + 2ATP
This is how Red Blood Cells ALWAYS conduct their cellular respiration
This prevents Red Blood Cells from using up the oxygen that they are carrying.
This Lactate then leaves the Red Blood Cells and goes to the Liver where it is turned back into Glucose.
The process of creating glucose from lactate requires 6 ATP and 2 Lactates = 1 Glucose.
Cori Cycle: 6ATP + 2 Lactate = 1 Glucose
The problem is that the process of recreating glucose uses more ATP (6) than the (2) ATP generated through anaerobic respiration.
So it is a net debt.
However, the Red Blood Cells don't have to worry about the debt as the Liver does Aerobic respiration and will pay it back from its abundance of ATPs.
Muscle cells can also burn the lactate in the presence of oxygen by turning it back into pyruvate.
There is always Anaerobic Respiration occurring in your body due to the type of cellular respiration occurring in the Red Blood Cells.
This means that lactate is always being produced in low levels and the liver is always turning it back into glucose. Alternatively, the Liver will just burn it
We don't notice this
We do notice when our muscles conduct large levels of Anaerobic Respiration
This is because Lactate easily turns into Lactic Acid - this contributes to the pain in the muscles that are conducting high levels of Anaerobic Respiration
Lactate can be burnt by muscle cells as well, once oxygen has arrived
The arrival of oxygen means that the mitochondria is open for business
The 3 Carbon Lactate is turned back into the 3 Carbon Pyruvate
This then enters the mitochondria and undergoes aerobic respiration
Speed of Muscle Activity and the type of Respiration used
Very fast = Throw a ball = ATP only (and Creatine phosphate)
Fast = Hold onto a Monkey Bar or go for a sprint = Anaerobic respiration
Medium = Go for a run = Aerobic Respiration
We know that there are very fast movements that we can do - like catching a falling cup. These superfast movements use just the ATP that is already in the muscle cells. They don't need anything burnt. Rather, after that hard throw a quick rest is taken by the muscle and aerobic respiration will top back up the used up ATP
Then you have fast but longer movements, like sprinting at your max or doing an arm-wrestle with your max strength, or holding onto the jungle gym by one hand.
In these moments your muscles are working fast. They use up all the ATP and then more is made. But this is made faster than oxygen can get into the cells, so it is made by anaerobic respiration.
When too much lactate is made, you will have to stop. This is the limit to how long you can 'sprint' or hold onto the jungle gym with one hand
Oxygen Debt
This process of burning lactate in the mitochondria once oxygen supply catches up and the mitochondria 'reopens' is referred to as the Oxygen Debt.
This Oxygen Debt is the reason you keep breathing heavily after intense exercise - you are getting oxygen into your muscles to burn the lactate that has built up.
Energy, from the Sun to your Proteins
