Following rules is very important in human society as well as in the cellular world. The difference is, cells follow rules “religiously” while humans tend to circumvent or even break or bend the rules. Maybe one of the reasons why we have problems in society is because we tend to do just that – either circumvent rules or break them.
I think we can learn a thing or two from cells. In the cellular world, everything flows smoothly. There is no chaos or anarchy. Why is this so? Well, because cells follow the rules or laws of nature.
For example, take a look at how cells generate energy...
When cells generate energy, they follow steps so there is no build up of both resources and products. There is always an enzyme that facilitates all processes every step of the way. Every process flows smoothly. No step is ever by-passed, there are no short cuts. The metabolic pathway that is followed is always the one that is the most energy efficient given the resources available. Every molecule in the cell "knows" its role and just awaits its turn to play its role. There is no jockeying for position because each molecule has its own time and place for action. There is no "me first, you later" in the cellular world.
Cells follow the rules of nature. We have the choice whether to follow rules of man or of nature. We have choice or freedom to choose, cells don’t have. So maybe there is really no parallelism. Cells “can’t help it” (but follow) but we can choose to follow or not. However, I strongly believe that if we just listen to our heart, we will also choose to follow the “laws of nature”.
In the cellular world, cells follow the laws of nature because these are programmed into their cellular “being”. I believe that in the human world we also have similar “laws of nature” programmed into our own being. However, we have problems knowing what these laws are because they are sometimes masked by the many distractions we have along the way. Many of us are beginning to sense however that indeed there are laws of nature that are also programmed in us. This is the reason why books like “A Purpose Driven Life” for example are so popular these days. We are now beginning to discover what our own “laws of nature” are.
Cells “know” their laws of nature and follow them “religiously” as I said earlier. We are just beginning to discover or rediscover our very own “laws of nature”. Once we do that and follow them, then I’m sure that our world will also flow as smoothly as that of the cellular world.
Showing posts with label energy generation. Show all posts
Showing posts with label energy generation. Show all posts
Thursday, January 29, 2009
Saturday, January 24, 2009
CoQ, do we really need it?
Why is there so much hype about the importance of CoQ or CoenzymeQ (a.k.a. CoQ10, ubiquinone)? Do we really need it?
Well, CoQ is a naturally occurring substance that is found in our membranes especially the membranes of the ER (see Nov 21, 23), peroxisomes (see Nov 15), lysosomes (see Nov 19), and vesicles (see Jan 11). It is most abundant in the cristae of our mitochondria (see Jan 1-5) as it functions as one of the electron acceptors during energy production.
Because it can accept and transfer electrons, CoQ can therefore act as antioxidant too. Thus, it is usually recommended as a dietary supplement especially in adults and individuals with diminished energy-producing capacity.
There is thus a biological basis for all the hype about this substance. However, its role in preventing heart failure still has to undergo more tests.
Since CoQ is fat soluble, it is best taken during meals that contain oil and fat.
Well, CoQ is a naturally occurring substance that is found in our membranes especially the membranes of the ER (see Nov 21, 23), peroxisomes (see Nov 15), lysosomes (see Nov 19), and vesicles (see Jan 11). It is most abundant in the cristae of our mitochondria (see Jan 1-5) as it functions as one of the electron acceptors during energy production.
Because it can accept and transfer electrons, CoQ can therefore act as antioxidant too. Thus, it is usually recommended as a dietary supplement especially in adults and individuals with diminished energy-producing capacity.
There is thus a biological basis for all the hype about this substance. However, its role in preventing heart failure still has to undergo more tests.
Since CoQ is fat soluble, it is best taken during meals that contain oil and fat.
Friday, January 23, 2009
Why is it better to water plants in the morning?
Why is it better to water plants in the morning? Why, because water is needed by plants in the light-dependent phase of photosynthesis.
Plants and other photosynthetic organisms start the light-dependent phase of photosynthesis as soon as there is light. During this process, light energy trapped by chlorophyll splits water into an oxygen molecule and 4 protons. The oxygen diffuses out of the plants (and this is what we breath in) while the protons (or hydrogen ions) are used to generate energy molecules.
What happens then if we water our plants late in the afternoon? Well, I think you know the answer to that - this does not give the plants enough time to generate more energy as well as to release more oxygen.
The energy molecules generated here are used for the carbon fixation or the light-independent phase of photosynthesis.
By the way, since plants release oxygen during this process, this is another reason why we have to thank a green plant. Don’t you agree?
Plants and other photosynthetic organisms start the light-dependent phase of photosynthesis as soon as there is light. During this process, light energy trapped by chlorophyll splits water into an oxygen molecule and 4 protons. The oxygen diffuses out of the plants (and this is what we breath in) while the protons (or hydrogen ions) are used to generate energy molecules.
What happens then if we water our plants late in the afternoon? Well, I think you know the answer to that - this does not give the plants enough time to generate more energy as well as to release more oxygen.
The energy molecules generated here are used for the carbon fixation or the light-independent phase of photosynthesis.
By the way, since plants release oxygen during this process, this is another reason why we have to thank a green plant. Don’t you agree?
Thursday, January 8, 2009
Counting ATPs
Students usually ask me how to count the number of ATPs formed during cell respiration. So I have prepared the following table that summarizes how and where ATPs are formed.
Before we go to that however, I just wish to point out that there are two ways by which ATP is formed. One is through substrate level phosphorylation and the other is through oxidative phosphorylation. During substrate level phosphorylation, 1 molecule of ATP is formed during each process. During oxidative phosphorylation however, 2 or 3 molecules of ATP are formed per process depending on the first hydrogen acceptor. If FAD is the first hydrogen acceptor, then 2 ATPs are formed while 3 ATPs are formed if NAD is the first hydrogen acceptor.
Another thing, we have to multiply by 2 all the ATPs formed because there are 2 molecules of pyruvic acid formed after glycolysis.
Reaction Type of Phosphorylation ATPs formed
Glucose to Pyruvic acid Substrate level 2 (net)*
Pyruvic acid to Acetyl CoA Oxidative 3 x 2
Krebs cycle and Ox-Phos Oxidative (NAD) 9 x 2
Krebs cycle and Ox-Phos Oxidative (FAD) 2 x 2
Krebs cycle Substrate level 1 x 2
G3P to 1,3DPGA in glycolysis* Oxidative via GP shuttle 2 x 2
* 4ATPs are actually formed. However, 2ATPs are used to prime glucose for the process.
**one step during glycolysis converts glyceraldehyde3phosphate(G3P) to 1,3diphosphoglycerate(1,3DPGA). This releases hydrogen ions and electrons that are accepted by NAD and brought to the mitochondrion through a glycero-phosphate shuttle (GP). So only 2 ATPs (instead of 3) are formed here (even if NAD is the acceptor) because 1 ATP is used to "pay" the GP shuttle.
Before we go to that however, I just wish to point out that there are two ways by which ATP is formed. One is through substrate level phosphorylation and the other is through oxidative phosphorylation. During substrate level phosphorylation, 1 molecule of ATP is formed during each process. During oxidative phosphorylation however, 2 or 3 molecules of ATP are formed per process depending on the first hydrogen acceptor. If FAD is the first hydrogen acceptor, then 2 ATPs are formed while 3 ATPs are formed if NAD is the first hydrogen acceptor.
Another thing, we have to multiply by 2 all the ATPs formed because there are 2 molecules of pyruvic acid formed after glycolysis.
Reaction Type of Phosphorylation ATPs formed
Glucose to Pyruvic acid Substrate level 2 (net)*
Pyruvic acid to Acetyl CoA Oxidative 3 x 2
Krebs cycle and Ox-Phos Oxidative (NAD) 9 x 2
Krebs cycle and Ox-Phos Oxidative (FAD) 2 x 2
Krebs cycle Substrate level 1 x 2
G3P to 1,3DPGA in glycolysis* Oxidative via GP shuttle 2 x 2
* 4ATPs are actually formed. However, 2ATPs are used to prime glucose for the process.
**one step during glycolysis converts glyceraldehyde3phosphate(G3P) to 1,3diphosphoglycerate(1,3DPGA). This releases hydrogen ions and electrons that are accepted by NAD and brought to the mitochondrion through a glycero-phosphate shuttle (GP). So only 2 ATPs (instead of 3) are formed here (even if NAD is the acceptor) because 1 ATP is used to "pay" the GP shuttle.
Tuesday, January 6, 2009
junk food and energy generation
Have you ever wondered why we call certain food as “junk food”? We usually understand that “junk food” has little or no nutritional value, right? Well, that is correct in a certain sense. However, there is another aspect to why “junk food” is junk, and this is related to what we have just covered in the last few posts about energy generation in cells.
One important process in energy generation is the maintenance of the proton gradient (see Jan 4 post). As mentioned: “This gradient drives the ions to move back to the matrix and as the ions pass through special channels that are associated with ATP synthase, ADP is phosphorylated to ATP.”
As you can see, the proton gradient is the one that drives the (hydrogen) ions to move back to the matrix and as they pass through special channels, energy (ATP) is created. If this gradient therefore is reduced or dissipated, then the driving force will no longer exist and no ATP is formed.
So what does this have to do with junk food? Well, here’s the connection. Some junk foods contain chemicals (usually the preservatives or coloring used) that reduce this proton gradient or driving force. How? These chemicals sequester or “smuggle” across the membrane the hydrogen ions without passing through the special channels with ATP synthase. Thus, no ATP is formed.
So, do you still wonder why “junk food” is junk?
One important process in energy generation is the maintenance of the proton gradient (see Jan 4 post). As mentioned: “This gradient drives the ions to move back to the matrix and as the ions pass through special channels that are associated with ATP synthase, ADP is phosphorylated to ATP.”
As you can see, the proton gradient is the one that drives the (hydrogen) ions to move back to the matrix and as they pass through special channels, energy (ATP) is created. If this gradient therefore is reduced or dissipated, then the driving force will no longer exist and no ATP is formed.
So what does this have to do with junk food? Well, here’s the connection. Some junk foods contain chemicals (usually the preservatives or coloring used) that reduce this proton gradient or driving force. How? These chemicals sequester or “smuggle” across the membrane the hydrogen ions without passing through the special channels with ATP synthase. Thus, no ATP is formed.
So, do you still wonder why “junk food” is junk?
Monday, January 5, 2009
energy generation in the mitochondrion, a summary
I have made this concept map to summarize all the processes of energy generation in the mitochondrion. I hope that you find it useful.
Saturday, January 3, 2009
Energy generation in the mitochondrion, part 2
source of image: www.britannica.com
As mentioned in yesterday’s post, the next 2 phases of energy generation in cells are Krebs’ cycle and oxidative phosphorylation.
Krebs’ cycle is also known as citric acid cycle because the first substrate formed is citric acid. This process occurs in the matrix of the mitochondrion.
This cycle is an 8-step process that changes AcetylCoA to citric acid and the latter into oxaloacetate. Main products of this cycle are Hydrogen ions and electrons which are immediately received by Hydrogen acceptors and transferred to the last phase or oxidative phosphorylation. By-products of this cycle are CO2 and H2O.
Only 2 ATPs are actually produced in the Krebs’cycle itself. However, since it is coupled with the last phase, oxidative phosphorylation, 22 more ATPs are produced through the coupled reactions.
We will talk about the last phase of this energy generation in tomorrow’s post.
Friday, January 2, 2009
Energy generation and the mitochondrion
Energy generation or cell respiration consists of 4 phases: glycolysis, conversion of pyruvic acid to Acetyl Coenzyme A, Krebs’ cycle and oxidative phosphorylation.
The last 3 phases of energy generation take place inside the mitochondrion while the first phase takes place in the cytoplasm of a cell.
Glycolysis is an anaerobic process (does not need oxygen to proceed) that involves breaking down of a sugar molecule (usually glucose) into 2 molecules of pyruvic acid. If oxygen is still not available after this process, then pyruvic acid is converted into lactic acid in animal cells and into ethyl alcohol in plant cells.
If oxygen is available however, the 2nd phase of energy generation takes place, that is, pyruvic acid is converted to Acetyl Coenzymne A in preparation for the 3rd phase of the process.
Glycolysis yields 4 molecules of ATP (the energy currency of cells) but the net yield is only 2 molecules of ATP because 2 molecules are used up to prepare glucose for the process. On the other hand, phase 2 or the conversion of pyruvic acid to AcetylCoA yields a net of 6 ATP molecules.
The last 2 phases of cell respiration are coupled. That is, one cannot occur without the other. We will thus talk about these 2 in another post.
The last 3 phases of energy generation take place inside the mitochondrion while the first phase takes place in the cytoplasm of a cell.
Glycolysis is an anaerobic process (does not need oxygen to proceed) that involves breaking down of a sugar molecule (usually glucose) into 2 molecules of pyruvic acid. If oxygen is still not available after this process, then pyruvic acid is converted into lactic acid in animal cells and into ethyl alcohol in plant cells.
If oxygen is available however, the 2nd phase of energy generation takes place, that is, pyruvic acid is converted to Acetyl Coenzymne A in preparation for the 3rd phase of the process.
Glycolysis yields 4 molecules of ATP (the energy currency of cells) but the net yield is only 2 molecules of ATP because 2 molecules are used up to prepare glucose for the process. On the other hand, phase 2 or the conversion of pyruvic acid to AcetylCoA yields a net of 6 ATP molecules.
The last 2 phases of cell respiration are coupled. That is, one cannot occur without the other. We will thus talk about these 2 in another post.
Thursday, January 1, 2009
Mitochondrion
source of image: www.britannica.com
I thought a good way to start the New Year right is to talk about cell energy and the mitochondrion.
The mitochondrion is an organelle that is involved in energy production. It is a rather complex organelle, it will probably take a few posts to completely its story.
Anyway, just to get started, let’s first talk about its structure today.
A mitochondrion (plural, mitochondria) is usually rod-shaped but this shape can change at anytime under varying conditions. It has a double membrane, the outer one being smooth and the inner one being thrown into folds called cristae (sing. crista). These folds increase the area for enzymes embedded in it and the more active a cell is, the more folds there are. Thus, a heart muscle cell for example has more cristae in its mitochondrion compared with a cartilage cell's mitochondrion.
There is a narrow space between the outer and inner membranes of the mitochondrion. This space is called the intermembrane space. Another space is found in the middle of the mitochondrion and this is called the matrix space or simply the matrix. Contents in both spaces differ.
The contents of the intermembrane space are somewhat similar to that of the cytosol whereas the matrix space contains many enzymes involved in the Kreb’s cycle process. Ribosomes as well as a circular DNA and tRNA are also found in the matrix.
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