Part 2
Following on from the above I started to put together all the aspects of metabolism of foods within our diets. This was spurred further from members who were interested in knowing a bit more about the body. A lot of this is researched, and pulled from text books, some is from memory and there may well be spelling mistakes or aspects I've missed out completely - list the questions and I'll answer it. I ended up going a bit heavy in some places, but I kept it within the realms of my knowledge - but I thought a bit of science wouldn't do any harm.
Some useful reading for you would be looking up the Krebs cycle, alanine cycle, ATP etc... You'll no doubt find lots of things wanting to research.
Metabolism of our major nutritional elements - we all know them, carbs, protein and fats. Each element behaves slightly differently here's a quick explanation/overview of each process.
Carbs
The structure of carbs is carbon, hydrogen, and oxygen atoms. And are classified as mono/di/poly saccharides, depending on the amounts of sugar units that make them up. The monosaccharides (I always spell this wrong) glucose (our well known element!), galactose, and fructose are obtained by digesting food within the intenstins via the intenstinal mucosa into the portal vein which goes to the liver.
Typically they are used for immediate energy release/use, in a temporary state is stored as glycogen (in the liver and muscles as we all know, or longer term converted to fats/amino acids and other compounds which I don't know fully! The longer term fat storage is what we want to avoid, hence why too many carbs and not enough activity ain't good!
Just to go off on a slight tangent for further explanation (and I think this is reasonably accurate) breaking down carbs plays an important role in both types of diabetes. For glucose to enter most tissues (muscles (so could include the heart too), adipose tissue, etc...) it's dependent on insulin being there (we've all heard of insulin spikes and response). As most of you know insulin controls the uptake (and effectively the metabolism) of glucose into those cells. Furthermore, and more widely known (and mentioned by me more than enough times!) plays a major role in regulating the blood/sugar levels, which is basically the concentration of glucose in the blood.
This reaction cannot take place without B vitamins being available, which function as coenzymes (they enable the biological functions to occur). The following are also important cofactors (I think this is the full list, but happy to be corrected). Iron, Zinc, Magnesium, Copper, Phosphorous, copper, manganese, and chromium (anybody know any more if that's right?).
Ok back on track, breaking down carbs or for carb metabolism to occur starts with glycolysis, this is the release of energy from glucose or glycogen to form two molecules of pyruvate. This then enters the Krebs cycle (remember that from biology? Wish I had spent more time paying attention!
), a process which requires oxygen, and as such they are completely "oxidised".
However, before the Krebs cycle can start, the pyruvate mollecules loses a CO2 gorup which forms this coenzyme I mentioned in another thread called acetyl COA. (I don't know about you, but my head hurts - it's been a while since I've brushed up on biology like this!
) This reaction is irreversible. This conversion of pyruvate to acetyl-CoA requires the B vitamins which is the cofactor I spoke about before - a facilitator of a bilogical process.
Phew. It gets easier, and onto more "relevant" BB stuff soon I promise!
However, it's important to understand all the bits and pieces. Sure, you could have looked this all up yourself, but hopefully I'm putting it across in such a way that makes sense? I might draw a diagram too if I can make it make sense...
The hydrogen from carbs is transported to where the energy is conserved in ATP molecules. ATP molecules are: Adenosine Triphosphate. And basically is a compound used to transfer energy between cells - a bit like a token ring network, they carry the tokens with the energy for other cells to use. But instead of data it transports chemical energy within cells for metabolism. Metabolic processes that use ATP as an energy source change it back into what it was before, as such it's continuously recycled within our body.
Interesting fact: our bodies on average contains 250 grams of ATP and turns over its own weight in ATP every day!!!
One molecule of glucose gives over 30 ATP molecules.
Very few cells (kidney & liver for example) can produce their own glucose from amino acids (from proteins normally, but not always). Furthermore, only liver and muscle cells store glucose in the form of glycogen (yawn we've heard that before!), so because of this the bloodstream is used to transport it to other cells (hence the blood sugar levels again).
It's a bit of a circular event!
Anerobic conditions (often associated with weight lifting rather than cardio etc...), lactate is formed from pyruvate (that chemical again!). This is an important even as to when the muscle's performance and use exceeds the oxygen supply to it. Glycolysis occurs in the fluid portion of a cell and has a double edged role. It breaks down the monosaccharides (remember from my first paragraph?) to generate energy,
as such it also provides glycerol for triglyceride synthesis. The Krebs cycle and the electron transport chain occur in the mitochondria (The mitochondria are the power plants for cells basically because they generate most of the cell's supply of ATP (inter cellular energy - I'll go into that later). Most of the energy derived from carbohydrate, protein, and fat is produced via the Krebs cycle and the electron transport system. (Do you need me to explain what the mitochondria is and what the electron transport system is?)
(The bit in italics is just copied from a text book as I couldn't remember what the full process was - so I hope it makes sense as it's getting to my limit of knowledge and ability to explain!
Back onto more familiar ground....
Glycogenesis is the conversion of excess glucose to glycogen. I think we all knew that. This often occurs a few hours after a meal or often also, in your sleep. This happens in the liver or, in the absence of a chemical called "glucose-6-phosphate" in the muscle, into lactate. Gluconeogenesis also is the formation of glucose in non carb sources, such as certain amino acids and the glycerol fraction of fats when carb intake is limited. (I'll go onto protein and carbs later). However in spite of all this, the liver (the most amazing organ in the world - I think it's just fascinating - if ever I were to become a doctor this would be my field I think, I love it... it's good to eat too!
) is the main area for gluconeogenesis. However on a side note and for your edification during starvation, the kidney becomes important in that process. Disorders inhibiting carb metabolism include diabetes, more recently discovered lactose intolerance, and galactosemia to name a few.
Right that's carbs, complicated old beast innit? Well, proteins are next, and probably slightly more complicated....
Fats are easy though - so I've left them till last!
Proteins!
These are made up of carbon (the chemcial of life), hydrogen, oxygen, nitrogen, maybe others but these are the main ones we need to worry about. The are the cellular structural elements (the keys behind elements (this could be foods, chemicals etc... an element is anything with a structure - do you get what I mean?). They are biochemical catalysts (things which speeds up a reaction or a process. They also are important regulators of gene development. Nitrogen (the important nitrogen balance we keep going on about in bodybuilding) is absolutely critical to the formation of 20 different amino acids (another common term). Amino acids are the building blocks of all the cells in the body.
On that point about nitrogen balance:
A positive value is what we want as it typically is found during periods of growth typically in the young, and more importantly for adults tissue repair (i.e. muscles!). This basically means you're taking in and storing a bigger pool of nitrogen than using it.
A negative value is basically the opposite, it means you're ill, or fasting and not in a state of growth.,
When you eat/digest proteins, all that means is that you're breaking it down to amino acids it really is that simple. If you take in excessive amounts of amino acids i.e. beyond your body's need, they are metabolised to glycogen (whoohoo that compound again! ) or fat and subsequently used for energy metabolism (which I touched on already). If amino acids need to be used for energy, then their carbon skeletons are converted to acetyl CoA (cha-ching!), which enters the Krebs cycle (hello again!) for oxidation, which produces????? (Go on guess....) Yup, ATP. You see you're learning!
The final products of protein catabolism include carbon dioxide, water, ATP, urea, and ammonia. Hence why excess protein breakdown can lead to kidney issues, but we're talking silly amounts here - like kilos of protein daily for years. (Ok I exaggerate maybe a little too much)
Vitamin B 6 (remember the vitamin B I was telling you about - which is why if you ever take any vitamins, B complexes and D are the 2 most important... I digress) is involved in the metabolism well, catabolism technically, of amino acids, as a cofactor (Remember what I said about coeznymes/cofactors??) that facilitates the transfer of nitrogen from one keto acid (an acid containing a keto group in addition to the acid group) to another. This is the last step of synthesis of nonessential (important!) amino acids and the first step in amino acid catabolism.
Transamination converts amino acids to L-glutamate. This is goes through the oxidation process and forms amonia used to synthesis urea. Urea is then transferred through the blood to the kidneys and goes out in pee form!
Now for the fun and intersting part!!
The glucose-alanine cycle is the main pathway that amino groups from muscle amino acids!! Aha! This is more like it! These amino acids are transported to the liver for conversion to glucose. The liver (again so so cool) is the main area of catabolism for all EAAs, except BCAAs, which are broken down mainly by muscle as well as the kidneys. Plasma amino-acid levels (i.e. the amount of AAs in your blood stream) are affected by carbs through insulin levels. As insulin increases it lowers plasma amino-acid levels (in particular BCAAs) by promoting the entry into muscles. Hence why insulin spikes post work out can be advantageous. However I stand by comments re: before bed, as GH is inhibited by insulin and GH is vital for repair and development - but I've already talked about GH.
Proteins within the body are broken down if/when the supply of energy through food/diet is inadequate. Often during illness or prolonged starvation - hence why when ill it's important to eat low carb high protein. The proteins within the liver are used first instead to those in other tissues such as the brain (which is understandable). The gluconeogenesis pathway is present only in liver cells and a few kidney cells.
Disorders of amino acid metabolism include (this is just a list pulled off the net): phenylketonuria, albinism, alkaptonuria, type 1 tyrosinaemia, nonketotic hyperglycinaemia, histidinaemia, homocystinuria, I found another one... one called maple syrup urine disease.
Fats! aka Lipids
Fats are made mostly of carbon and hydrogen, some oxygen, and undoubtedly other atoms too. The three main forms of fat found in food are:
glycerides (in principle, triglycerol (triglyceride), this is the form where fat is stored for fuel)
phospholipids sterols (in particular cholesterol (I'll touch on that again below though I know I've done a piece on it already).
Fats provide around 8cals per gramme, vs 4cal/g for proteins and carbs - we've all been briefed on this.
Triacylglycerol, in whatever form it comes isn't taken up directly by any tissues. It has to be hydrolysed (broken down by water) outside any tissue into a fatty acid as well as glycerol (hello again), only then can it enter the cell.
Fatty acids come from our diets, fat cells within foods, carbs, and some amino acids. After digestion, most of the fats are carried in the blood as chylomicrons. The main pathways of fat breakdown are: lipolysis, betaoxidation, ketosis (we've heard of this before haven't we chaps?
) and lipogenesis.
Lipolysis and beta-oxidation occurs in the mitochondria (that wonderfl cell again!). It is another one of the cyclical processes where two carbons (seems common this carbon stripping!) are removed from the fatty acid every cycle in the form of acetyl CoA (again - simple this biology stuff isn't it?), which proceeds through the Krebs cycle to produce ATP, CO 2 , and water. Deja vu anyone?
Textbook definition time: "Ketosis occurs when the rate of formation of ketones by the liver is greater than the ability of tissues to oxidize them."
It basically occurs during prolonged bouts of "starvation" or alternatively, as we can relate to from previous conversations when large amounts of fat are eaten in the absence of carbs!
Lipogenesis occurs in the cytosol (liquid found in cells).
Triglyceride synthesis predominently happens within the liver, adipose tissue, and the intestines. The fatty acids are derived from the hydrolysis of fats as mentioned before, as well as from the synthesis of acetyl CoA through the oxidation of fats, glucose, and some amino acids.
Most of the major tissues (e.g., muscle, liver, kidney) are able to convert glucose, fatty acids, and amino acids to acetyl-CoA. However, brain and nervous tissue—in the fed state and in the early stages of starvation—depend almost exclusively on glucose. Not all tissues obtain the major part of their ATP requirements from the Krebs cycle. Red blood cells, tissues of the eye, and the kidney medulla gain most of their energy from the anaerobic conversion of glucose to lactate.
I know I've already got a section on cholesterol in my previous diatribe, but I thought I'd add more since I've got the page open at this section now!
As previously mentioned cholesterol is either obtained from our diets (to a lesser extent) or synthesised in a variety of tissues within the body, including the liver (yet again!), adrenal cortex, skin (believe it or not), intestine, testes, and aorta. High levels of cholesterol in your diet actually suppresses synthesis in the liver but not necessarily in other tissues... it's complimicated
Insulin has potential role to play with cholesterol as it's a pro-inflammatory hormone, which in combination with high glucose levels results in more oxidative damage to tissue. As a result a generalised inflammatory state is created typically marked by inflammations on the walls of blood vessels. Cholesterol is basically the plugging agent/concrete/mortar of the body and is found everywhere within the body. The cholesterol is there to patch up the inflammation. When the body needs to take cholesterol out of the blood stream to do this LDL is perfect as it hovers on the "outside" of the blood vessels, and HDL in the middle. IT's the LDL that is the "mortar" that sticks to the blood vessels to fix them. But if the body needs cholesterol to go back to the liver, insulin is transported via HDL instead as it floats in the "middle" of the blood stream. Hence the ratio of HDL and LDL. (High density, low density) is a good way of working out your body's inflammatory state. Restoring insulin sensitivity decreases that systemic inflammatory state, which results in less inflammation of the vessel walls therefore needing less cholesterol to be transported for this purpose on LDL molecules.
So high cholesterol is more of a symptom than a cause of cardiovascular disease. Correcting the underlying problem of high cholesterol is better than any cure, pills or anything else. Else it'll come back and you won't really have addressed the root cause of the problem. By addressing the issue the production of HDL becomes stronger and as such the ratio turns back into favourable areas.
The inflammatory state is largely but not solely related to the amount of circulating glucose and insulin in the body!
Reducing cholesterol isn't just following a hunter-gatherer type of diet with little to no carbs or any refined carbs. But also high intensity exercise/work - to deplete glycogen stores. However glucagon is nonamplifying, i.e. it's 1 for 1. So one molecule of glucagon will affect ONE molecule of glycogen. By doing high intensity exercises (HIIT being a good example), it aggressively empties glycogen, creating an enhanced insulin sensitivity situation as it becomes necessary for the body to be in that state. So you have to work at a high enough intensity to promote glycolytic cells to release their glycogen cells - and the reason it requires high intensity is that for any level of glucose ingested the amount of insulin that has to be secreted is much much lower. So the more sensitive you become the quicker your glucose metabolism becomes, ergo, your body becomes balanced once again.
If there are any terms, chemicals, enzymes that I've listed that don't make sense I can break them down for you - it's hard to write down the explanation fo every enzyme because:
a) I honestly don't know it all,
b) I only know that that enzyme/chemical is required but that's it
c) it would make it really a lot harder to read
I am getting to the edge of my knowledge here, and a lot of this required me to stick my nose in a text book (not google as I don't trust it!
) to make sure I got it right. I think I've got it right, but hopefully with this info and the advice I and others have given on diet/nutrition some of this makes sense?
