ProteinsBiol 135 Lecture: IV. Structure, Function and Source of Macronutrients.

C. ProteinsProteins are the most versatile and ubiquitous of the organic molecules in the human body. They are an integral part the body and are found throughout the structures and systems of the human body. At least 10,000 different proteins help to make up what you are. Like all other organic molecules that we ingest, proteins are crucial for normal growth and development of the body, especially critical for muscle and bones. They are literally everywhere, making up the ‘plasma proteins’ of the blood; they also form a major component of the plasma membrane of all cells; they function as receptors, transporters and enzymes. Proteins are also found in muscle, bone, skin, hair, and virtually every other body tissue. All the enzymes that catalyze the thousands of chemical reactions in the body are proteins! The very molecule that carries 98% of the oxygen (O2) from your lungs to you tissues is the protein molecule hemoglobin. With such varied and prominent functions, there can be a high turn-over of protein in the body, so it becomes very important to ensure adequate supply in your diet to match your needs.

Amino Acids Make Proteins Proteins are made from building blocks (or subunits) called amino acids. Our bodies make amino acids in two different ways: Either from scratch, or by modifying others. Some amino acids are called essential amino acids, because they must come from the food we eat in our diets. Animal sources of protein tend to deliver all the amino acids we need. Other protein sources, such as fruits, vegetables, grains, nuts and seeds, lack one or more essential amino acids.

Figure 1. Show the “Generalized Amino Acid” structure. Each of the 20 amino acid has a central Carbon (C) that is flanked on one side by an amino group (NH2) and on the other side by a carboxylic acid group (COOH). The central C as a H atom attached to is and lastly, is the R group which represents the “Variable” or “Functional” side group. It is R portion that makes each amino acid unique. The number and sequence of amino acids in each protein determines its unique shape and function.

Of the proteins that are made from the 20 different amino acids, 9 are essential, meaning humans cannot make them, but must eat them in their diets. The remaining 11 are not essential, as we can synthesize them in our bodies. The variable (R) group is this is the only part of the 20 amino acids in human nutrition that is different and unique to each.

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This side group (R) can be basic, acidic, polar, non-polar, charged, or neutral. The way this side group interacts with other side groups in the peptide chain will have an impact on its three dimensional (3D) shape. In the protein world, shape equals function, so the shape a protein takes is crucial to how that protein operates. If a protein loses its shape due to some type of stress (e.g., heat, change in pH, etc.) it can become denatured (change its shape) and loose its normal function (see later in this section).

The 20 Amino Acids: Building Proteins from Amino AcidsAs mentioned, for humans, an essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by humans and therefore must be supplied in our diet. The nine (9) essential amino acids for humans are: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine.

There are six (6) amino acids are considered conditionally essential in the human diet, meaning their synthesis can be limited under special pathophysiological conditions. These are: Arginine, Cysteine, Glycine, Glutamine, Proline and Tyrosine.

There are five (5) amino acids are dispensable in humans, meaning they can be synthesized in the body. These five are: Alanine, Aspartic Acid, Asparagine, Glutamic Acid and Serine.

Essential Amino Acids in Humans

Figure 2. The building of peptides, oligopeptides and proteins is done by using the amino acids listed in the table above. As shown in the diagram to the right, adding amino acids together in a linear sequence, the amino end always combines with the carboxylic end when making a covalent peptide bond. Two amino acids combine in a dehydration synthesis reaction to create a dipeptide. Can you Remember all of the Essential and Non- Essential Amino Acids?

Essential NonessentialHistidine Alanine Isoleucine Arginine Leucine Asparagine Lysine Aspartic acidMethionine Cysteine Phenylalanine Glutamic acid Threonine GlutamineTryptophan Glycine Valine Proline

Serine Tyrosine

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It may seem like a tall order at first, to remember 20 amino acids when you may not have even known one of their names prior to reading the list presented in Figure 2. A good way to remember anything that seems complicated at first is to see if there is a pattern you can create and use to help you remember things.

Often a mnemonic device or saying is a good tool that can be used to remember a long series of items or words. It is done by creating a saying that is easy to remember, typically by using the first letter of each word or structure in the series – then you substitute the ‘real words’ into the saying. Because the mnemonic saying easily triggers the pattern for the more complicated or less familiar set of terms, it can be very handy!

Here is a simple mnemonic for remembering the essential amino acids: PVT TIM H*LL. It can be read as “Private Tim Hall”, knowing that the nine capital letters in this saying represent the first letters of the nine essential amino acids.

P.V.T. P = Phenylalanine V = Valine T = Threonine

T.I.M. T = Tryptophan I = Isoleucine M = Methionine

H.L.L. H = Histidine L = Leucine L = Lysine

For the remaining 11 non-essential amino acids, there is sort of an easy way to put the capital letters that represent the amino acids in a memorable pattern:

AAAA CGGG PST

Four A’s, one C, then three G’s, then like “pst, over here” at the end.

Alanine Cysteine ProlineArginine Glutamic acid SerineAspartic acid Glutamine TyrosineAsparagine Glycine

Task: See if you can list all of the 20 amino acids in human nutrition, and differentiate between the 9 essential and 11 non-essential. The best way to do this is to write out the names fully – several times! *Note: You create and maintain at least 26 neural pathways every time you write by hand. You may have never even heard of an amino acid before now, but here they are and if you write out the 2 lists several times on a blank piece of paper, referring to the notes and

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using the mnemonics as a trigger, you will be surprised at how you can memorize these names. A little later, take a blank piece of paper and see how many you can write without looking at the notes. Practice until you can write them all out, and after that, it will be hard to forget!

Amino Acid Key for Figure BelowEssential NonessentialHistidine (His) Alanine (Ala)Isoleucine (Ile) Arginine (Arg)Leucine (Leu) Asparagine (Asn)Lysine (Lys) Aspartic acid (Asp)Methionine (Met) Cysteine (Cys)Phenylalanine (Phe) Glutamic acid (Glu)Threonine (Thr) Glutamine (Gln)Tryptophan (Trp) Glycine (Gly)Valine (Val) Proline (Pro)

Serine (Ser)Tyrosine (Tyr)

Figure 3. The 20 amino acids in 3 letter code, colors: Blue = amine; pink = acid; red = variable groups.

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Figure 4. Like ‘peals on a string’, the amino acids line up and form a peptide or protein of a unique length and sequence. The Primary Structure of a protein is the linear sequence of amino acids and is critical for determining how the entire structure will fold and behave.

The linear sequence of amino acids is very important - A great example of this significance is seen in the disease of sickle cell anemia. Sickle cell anemia gets its name from the abnormal shape of red blood cells in affected individuals, the red blood cells tend to collapse and give the cells an abnormal crescent shape, like a sickle appearance. This is in contrast to the normal bi-concave disc appearance of these cells. Due to a change in one amino acid in a chain of 126, these sickle shaped red blood cells are very fragile and the result is severe anemia from a decreased number of red blood cells. The abnormally shaped red blood cells in this disease also cause the blockage of blood vessels and other painful symptoms in patients.

Figure 5. The substitution of the 6th amino acid in the β-globin chain subunit of hemoglobin (Hb), from glutamic acid to valine, gives rise to changes in the shape and function of note only the Hb molecule, but also the entire red blood cell (erythrocyte). The result is ‘sickle cell anemia’ which impairs blood flow and oxygen delivery to tissues.

The abnormal shape of the cells in individuals with sickle cell anemia comes from a defective protein within the blood cells themselves. This defective protein is hemoglobin. The normal hemoglobin protein is made up of four parts, and therefore called a tetramer. Each part of the tetramer has the ability to bind an oxygen molecule and carry it from the lungs to the tissues in where oxygen is needed. When the defective hemoglobin in sickle cell anemia is present, it’s referred to as HbS and does not have an oxygen molecule bound to it, unlike the normal Hb that can combine with O2 it form oxyhemoglobin (HbO2). The HbS tends to form a

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precipitate made up of lots of hemoglobin proteins stuck to each other. This precipitate is what causes the red blood cells to become sickle-shaped.

Question:How many if the first 6 amino acids in the normal beta chain subunit are essential? = ______.

Peptide BondsFrom all of the unique side groups (R) of the 20 Amino Acids, all of the polypeptides, peptides and proteins are made. Amino acid chains are linked by covalent peptide bonds from dehydration synthesis (condensation) reactions.

a) Dipeptide = 2 amino acids joined by a peptide bond

b) Tripeptide = 3 amino acids joined by a peptide bond

c) Polypeptide = more than 10 amino acids joined by a peptide bond

d) Peptide = amino acid chain made of less than 50 amino acids

e) Protein = chain of more than 50 amino acids

Figure 6. This shows two amino acids undergoing a dehydration synthesis (condensation) reaction which involves the removal of a water (H2O) molecule to make a dipeptide. The covalent peptide bond holds the dipeptide together. This reaction is called Endergonic, because it requires the input of energy.

Proteins have amino acid sequences and lengths that are all different, and their shapes will depend on the chemistry of the side groups and how they interact with other portions of the peptide chain. The way that the string of amino acids are arranged may cause them to coil and twist the peptide chains that help to provide stability in its shape.Exercise: Draw the amino acids 1) glycine and 2) valine side by side below and show how by removing one water molecule (H2O) you could make a dipeptide.

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1) 2)

The Shape of a Protein = the Function of a Protein

The 3D shape of a protein in space has fundamental consequences on its actions, so we need to understand what the factors are that influence the overall shape of a protein.

Proteins have 4 Levels of Structure

Primary: The linear sequence of amino acids that are linked together by covalent peptide bonds.

Secondary: The geometric folding and twisting of the protein into α-helix or a β-pleated sheet.

Tertiary: Three-dimensional globular shape of the protein in space – caused by R group interactions.

Quaternary: Two or more polypeptide chains that bond together. Not all proteins will have this structure.

Figure 7. Shows the four Levels of Structure of Proteins. Not all proteins will have quaternary structures.

Denaturation of a Protein – Losing its Shape!

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Protein denaturation is the uncoiling of protein that changes its ability to function. Typically proteins can be denatured by heat and acid. After a certain point, denaturation cannot be reversed.

Figure 8. Comparison between a Normal protein and the same protein that has been Denatured. The denatured protein will lose most or all of its normal function. Some protein can recover from being denatured and some cannot, depending on the severity of the stress.

Proteins in the BodyAs mentioned several times, proteins are numerous, versatile and unique. The synthesis of a protein is determined by the genetic information encoded in your DNA. The way that information about proteins are stored, read and synthesized in the body will be very briefly explored. Proteins are a very dynamic group of molecules in the body, in that they are constantly being broken down and synthesized in the body. Researchers measure nitrogen balance to study synthesis, degradation and excretion of protein. Protein has many important functions in the body. The study of proteins is called proteomics.

Protein Synthesis is Unique for Each Person: Determined by the Amino Acid Sequence.Information about how to make the proteins we need is stored in the cell nucleus on your DNA in the form of genes. Genes are a specific sequence of nucleotides (there are 4: A, C, G and T) in the DNA molecule that code for a product your body will make, like a protein.

The specific gene on your DNA molecule is the long term record of the information (like a ‘blue print’) and proteins are made by generating a temporary copy of this gene (like a ‘photo copy’), called messenger RNA (mRNA).

The instructions on the gene are written and read in codons, which are like a 3 letter word made out of the nucleotides, each unique three letter word calls for a specific amino acid or signals the start or end of a protein chain.

This mRNA together with ribosomes and transfer RNA (tRNA) in the cytoplasm, work to assemble amino acids into peptides and proteins. The tRNA contains anticodons that ‘carry’ specific amino acids with it, bringing in the each new amino acid to add to the growing chain, connecting each amino acid with a covalent peptide bond to make proteins.

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Figure 9. Inside the cell, protein synthesis is shown, which involves Transcription and Translation.

Transcription is the process of making an RNA copy of a gene sequence, called a messenger RNA (mRNA). This occurs in the nucleus of the cell.

Translation is the process of translating the sequence of mRNA to a sequence of amino acids that will result in a protein. This occurs in the cytoplasm of the cell with ribosomes and tRNA.

Basic Steps in Protein Synthesis

1. In the nucleus, DNA unwinds, allowing a ‘complementary’ temporary copy of a gene to be made messenger RNA (mRNA). This is Transcription!

2. The mRNA moves from the nucleus into the cytoplasm and becomes associated with ribosomes.

3. Along comes transfer RNA (tRNA), which brings in the specific amino acid called for by the mRNA codon by matching it to the tRNA anticodon. This is Translation!

4. As translation continues, the incoming amino acids form a growing peptide and protein chain. This is Elongation!

5. Protein synthesis is terminated by a specific code on the mRNA and the completed protein is release from the ribosomes into the cytosol. This is Termination!

*Sequencing errors can cause alterations in proteins to be made; an example is sickle-cell anemia.

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Nutrients and Gene Expression Cells regulate gene expression - which means they ‘read’ genes such that the product of that gene is made by the body. Note: The term Epigenetics refers to a nutrient’s ability to activate or silence genes, i.e., control gene expression, without necessarily interfering with the genetic sequence. There is the possibility that our genes can also be changed. We have seen a great example of epigenetics in terms of the effect of diet in the Agouti mice study.

The Various Roles of ProteinWith the many a varied roles of proteins in the human body, it is worth taking a quick look at an overview of the roles of proteins in the body as at this time. When it comes to discussing types, sources and amounts of proteins in a healthy diet, we will have a better idea where and what this protein is used for. It will also be important to consider the utilization of proteins as fuel when our bodies are low on glucose stores. 1. Fibrous Proteins create structural matrix for Growth and Maintenance

a) Makes the protein collagen (the most abundant fiber in the human body) as a component of the matrix filled with minerals to provide strength to bones and teeth.b) Replaces tissues including the skin, hair, nails and GI tract lining.

2. Enzymes are biological catalysts (they speed up the rate of a chemical reaction in the body without being consumed). In this way, proteins facilitate anabolic and catabolic chemical reactions in the body. Many of these chemical reactions are crucial to the digestion of the ingested nutrients and

3. Hormones regulate many body processes and some hormones are protein. Important examples are insulin and glucagon, which regulate blood glucose levels.

4. Regulators of Fluid BalanceProteins that are suspended in the blood are called “Plasma Proteins”. These are critical to maintaining normal blood volume. The proteins create ‘colloid osmotic pressure’ in the blood. This force keeps water attracted to return back into to the plasma inside the blood vessel after it has been forced out of the blood vessel into the interstitium from hydrostatic pressure of the blood! Proteins also help to maintain the volume of body fluids in the interstitium and in this way prevent edema - which is excessive tissue fluid accumulating in the tissue spaces. This impairs gas exchange and tissue health. By helping to maintain the plasma and interstitial fluid volumes, it helps regulate the composition of body fluids.

5. Acid-Base Regulation occurs by certain proteins in the body. a) Act as buffers, able to resist changes in pH and therefore help maintain a stable pH. b) Acids are compounds that release hydrogen ions in a solutionc) Bases are compounds that accept hydrogen ions in a solutiond) Acidosis is high levels of acid in the blood and body fluidse) Alkalosis is high levels of alkalinity in the blood and body fluids

6. Transportersa) Carry lipids, vitamins, minerals and oxygen in the throughout the body, in blood and lymphatic vessels and across cell membranes.

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b) Act as glucose transporters or ion pumps in cell membranes. For example, the Na+/K+ Pump must exist in every living cell in order to continue living and to maintain the resting membrane potential (RMP) of that cell.

7. Antibodiesa) Fight antigens that invade the body such bacteria and viruses.b) Provide immunity to fight an antigen more quickly the second time exposure occurs.

8. Source of Energy and glucose if needed – this involves the deamination of amino acids so that they can be converted to glucose in a process called gluconeogenesis, which means making glucose from non-carbohydrate sources. Protein can be used for energy if needed; its excesses are stored as fat.

9. Other Rolesa) Blood clotting by converting fibrinogen into fibrin, which forms a solid blood clot.b) Vision by creating light-sensitive pigments rhodopsin in the retina.

Protein Metabolism

Key Steps in Protein Digestion and Absorption

In the Mouth: Unlike some starches and lipids that can begin some mild chemical digestion in the mouth, protein digestion does not commence until it reaches the stomach. The stomach is highly specialized to handle protein digestion. It starts when the chief cells in the gastric glands of the stomach release the powerful hydrochloric acid (HCl). Once HCl is made and released in the stomach the pH goes down to about 2, and this highly acidic environment denatures the protein strands after the bolus enters the stomach. The high level of HCl also triggers the conversion the digestive enzyme Pepsinogen (inactive form) to Pepsin (active form), which works on breaking polypeptides into shorter chains (through hydrolysis). The activation of a protein by cutting it is called “Proteolytic Activation”.

As the chyme in the stomach is moved to the first portion of the small intestine called the duodenum, the digestion of protein continues because the protein content in the stomach triggers the release of the hormone cholecystokinin (CCK) from the mucosal epithelium of the duodenum small intestine and secreted. This causes the release of further digestive enzymes and bile from the pancreas and gallbladder, respectively.

Cholecystokinin (from Greek chole, "bile"; cysto, "sac"; kinin, "move") is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. Cholecystokinin also acts as a hunger suppressant.

The pancreas is stimulated to secrete proteases*, which continue the breakdown of peptide bonds into smaller peptide chains and single amino acids in the small intestine.

*Note: Words that end in –ase denote an enzyme in biology.

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Although the 20 amino acids are different chemically and structurally from each other, all of them are small enough in terms of their molecular weights to be absorbed from the cells of the small intestine directly into the blood stream. From there they are transported via the hepatic portal system to the liver.

Amino Acids and Proteins in the LiverIn the liver, amino acids are used to synthesize new proteins or are converted to energy, glucose, or fat. Some whole proteins are absorbed intact, such as antibodies from breast milk. It appears that the most common type of novel peptide fragments we might encounter in our diet are produced by genetically modified (GM) foods. When these novel (meaning not naturally encountered in our diet) protein fragments are absorbed by the small intestines into the blood stream of the body, they are viewed as foreign pathogens and this generates an exaggerated immune response - based on the protective physiological mechanisms of our body. What occurs is inflammation and aggravation of the body’s defense systems. These are otherwise known as food allergies.

How Are Amino Acids Metabolized?Depending on the body’s need for protein, the liver determines the fate of newly absorbed amino acids. If an individual is not eating sufficient carbohydrates, amino acids can be converted to glucose through a process called gluconeogenesis.

Gluconeogenesis = making glucose from non-carbohydrate molecules, such as proteins and fats.

Most amino acids travel to the blood for use by cells. The ‘amino acid pool’ in cells supply the body’s ongoing needs for protein synthesis. The daily wear and tear on the body causes the breakdown of hundreds of grams of proteins each day. If you are sick, wounded, burned, injured or have been vigorously active, extra protein may be needed for healing purposes. The amino acid pool is the newly absorbed amino acids and component parts from degraded or broken-down cellular proteins. This can be used to create proteins on demand.

More than 200 grams of protein are turned over each day. Almost 50 percent of this protein turnover (the process of degrading and synthesizing of protein) occurs in the intestines and the liver. The remaining turnover has other uses, such as the replacement of skin cells and red blood cells or in the synthesis of thyroid hormones and melanin.

Amino Acids Catabolism for FuelAmino acids are used for different purposes in our body. Most of the metabolic pool of amino acids is used as building blocks to make proteins, and a smaller proportion is used to synthesize specialized nitrogenated molecules as epinephrine and norepinephrine, neurotransmitters and the precursors of purines and pyrimidines.

Since amino acids cannot be stored in the body for later use, any amino acid not required for immediate biosynthetic needs is deaminated and the carbon skeleton that remains is used as metabolic fuel (10-20 % in normal conditions) or converted into fatty acids via acetyl CoA. The main products of the catabolism of the carbon skeleton of the amino acids are: Pyruvate, oxalacetate, a-ketoglutarate, succinyl CoA, fumarate, acetyl CoA and acetoacetyl CoA.

When carbohydrates are not available (starvation, fasting), or cannot be used properly, as in diabetes mellitus, amino acids can become a primary source of energy by oxidation of their

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carbon skeleton, but also by becoming an important source of glucose for those tissues that only can use this sugar as metabolic fuel.

The formation of glucose from amino acids (gluconeogenesis) in liver and kidney is intensified during starvation and this process becomes the most important source of glucose for the brain, RBC’s and other tissues. During a situation of prolonged starvation, this can be viewed as an “emergency” and amino acids in skeletal muscle proteins can be used as an energy store, yielding 25,000 kcal.

In terms of the metabolic fate of the carbon skeleton, Amino Acids can be classified as:

Glucogenic: Amino acids whose catabolism yields to the formation of Pyruvate or Krebs Cycle metabolites, that can be converted in glucose through gluconeogenesis.

e.g., Alanine, Arginine, Asparagine, Aspartate, Cysteine, Glutamate, Glycine, Histidine, Methionine, Proline, Serine, and Valine.

Ketogenic: Amino acids that yield acetyl CoA or acetoacetyl CoA (e.g. they do not produce metabolites that can be converted in glucose).

e.g., Lysine and Leucine (exclusively).

Glucogenic and Ketogenic: Amino acids that yield some products that can become glucose and others that yields acetyl CoA or Acetoacetyl CoA.

e.g., Isoleucine, Phenylalanine, Tryptophan, Tyrosine and Threonine.

Figure 10. The metabolism of amino acids for fuel in the body, showing the glucogenic and ketogenic pathways that the various amino acids take.

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Deamination removes the Amine group from Amino Acids.If amino acids are not sufficiently required by the body, the amino group must go through a process called deamination - where the amine group is removed and converted to ammonia (NH3). This is then sent to the liver to be converted to the less toxic urea and eventually excreted in the urine. After the removal of the nitrogen, the remnants of the amino acids can be converted to glucose, used as energy, or stored as fat.

O Urease

H2N – C – NH2 + 2H2O + H+ 2NH4+ + HCO3

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urea water hydrogen ammonium bicarbonate ion ion ion

Nonessential amino acids are synthesized through the process of transamination; the liver transfers an amino group to the keto acid, creating a new, nonessential amino acid and a new keto acid. Proteins can be used for gluconeogenesis; when bodily stores of glycogen are depleted, the body turns to glucogenic amino acids (amino acids converted to glucose through gluconeogenesis) to provide a new supply of glucose.

Excess protein cannot be stored per se as protein, it is converted to body fat; after deamination, extra carbon skeletons from protein are capable of being changed to fatty acids and stored as triglycerides in adipose tissue.

General Overview of Protein Metabolism1. Protein turnover is the continual making and breaking down of proteins in the bodyThe amino acid pool is the supply of amino acids that are available.

a) Amino acids from food are called exogenous.b) Amino acids from within the body are called endogenous.

2. Nitrogen Balance = Protein utilization in the body.a) Zero nitrogen balance is nitrogen equilibrium, when input is equal to output.b) Positive nitrogen balance is when nitrogen consumed is greater than nitrogen excreted.c) Negative nitrogen balance is when nitrogen excreted is greater than nitrogen consumed.

3. Using Amino Acids to Make Proteins or Nonessential Amino Acids – cells can assemble amino acids into the protein needed

4. Using Amino Acids to Make Other Compounds a) Neurotransmitters are made from the amino acid tyrosine.b) Tyrosine can be made into the melanin pigment or thyroxine.c) Tryptophan makes niacin and serotonin.

5. Using Amino Acids for Energy and Glucosea) No readily available storage form of proteinb) Breaks down tissue protein for energy if needed

6. Deamination of Amino Acidsa) Nitrogen containing amino groups are removed.b) The two products that result from deamination include ammonia and keto acids.

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7. Using Amino Acids to make Proteins or Nonessential Amino Acids (Transamination)

8. Converting Ammonia to Urea. The process of deamination of amino acids generate ammonia, which is a toxic substance. The liver is the organ of detoxification of the blood! Thus, ammonia and carbon dioxide (CO2) are converted in the liver into the much less toxic substance urea by the enzyme urease.

9. Excreting Urea. Urea is released back into the bloodstream where it is filtered out of the blood in the renal kidneys and excreted in urine. Increased water intake is necessary with a high-protein diet to flush the excess urea from the body.

a) Excess protein is de-aminated and converted into fat.b) Nitrogen is excreted.

Protein in FoodsEating foods of high quality protein is the best assurance to get all the essential amino acids. Complementary proteins can also supply all the essential amino acids. A diet inadequate in any of the essential amino acids limits protein synthesis. The quality of protein is measured by its amino acid content, digestibility, and ability to support growth.

Protein QualityThis can depend on the protein digestibility, which depends on protein’s food source: a) animal proteins are 90-99% absorbed and; b) plant proteins are 70-90% absorbed. Other foods consumed at the same time can have an impact on the digestibility of the proteins.

Use of Amino Acid in the Body: a) The Liver can produce nonessential amino acids.b) Cells must dismantle other nutrient molecules to produce essential amino acids if they are not provided in the diet. The limiting amino acids are those essential amino acids that are supplied in less than the amount needed to support protein synthesis.

Reference Protein is the standard to measure other proteins by. This is used in preschool children, based on the needs for growth and development for this group of developing children.

High-Quality Proteins – are those proteins which contain all the essential amino acids – they used to be called “Complete” proteins. Animal foods contain all the essential amino acids. Plant foods are diverse in amino acid content and tend to be missing one or more essential amino acids. There are also Complementary Protein – this is done by combining plant foods that together contain all the essential amino acids, a strategy that should be used by vegetarians.

Protein Regulation for Food Labels1. List protein quantity in grams2. % Daily Values is not required but reflects quantity and quality of protein used.

Protein-Energy Malnutrition (PEM), also called protein-kcalorie malnutrition (PCM)1. Classifying PEM.a) Chronic PEM and acute PEM.b) Marasmus or Kwashiorkor, or a combination of the two.

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MarasmusMarasmus is a form of severe malnutrition or impaired absorption of protein, energy, vitamins and, minerals; characterized by energy deficiency. A child with marasmus looks emaciated. This develops slowly and involves severe weight loss and muscle wasting.

Body weight is reduced to less than 60% of normal (expected) body weight for the age. Marasmus occurrence increases prior to age 1 (from infancy to 18 months of age), whereas kwashiorkor occurrence increases after 18 months.

It can be distinguished from kwashiorkor in that kwashiorkor is protein deficiency with adequate energy intake whereas marasmus is inadequate energy intake in all forms, including protein. Protein wasting in kwashiorkor may lead to edema (abnormal tissue swelling). Hair and skin problems ensue, can also affects the mental capacity, but a good appetite is possible. The prognosis is better than it is for kwashiorkor but half of severely malnourished children die due to unavailability of adequate treatment.

The word “marasmus” comes from the Greek μαρασμός marasmos ("decay").

Figure 11. Shows a photo of a typical example of a child suffering from Marasmus – a severe form of wasting from protein deficiency.

KwashiorkorKwashiorkor - a form of severe protein–energy malnutrition characterized by, irritability, anorexia, ulcerating dermatoses, edema (ascites) and an enlarged liver with fatty infiltrates. It develops after weaning from about 18 months to 2 years of age, with a rapid onset. Sufficient calorie intake, but with insufficient protein consumption, distinguishes it from marasmus.

Kwashiorkor cases occur in areas of famine or poor food supply. Cases in the developed world are rare. This name was entered the medical community in 1935 by pediatrician Cicely Williams, derived from the Ga language of coastal Ghana, translated as "the sickness the baby gets when the new baby comes". This reflects the development of the condition in an older child who has been weaned from the breast when a younger sibling comes.

Body weight is reduced to less than 60 to 80% of normal weight for the age. Breast milk contains proteins and amino acids vital to a child's growth. Some muscle wasting and some fat retention. In at-risk populations, kwashiorkor may develop after a mother weans her child from breast milk, replacing it with a diet high in carbohydrates, especially sugar, but deficient in

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protein (for example milk formulas). Hair and skin problems ensue, can also affects the mental capacity with a loss of appetite.

Figure 12. Shows a comparison between two children suffering from Kwashiorkor and Marasmus, The distended belly caused by edema is a fast way to differentiate the two disorder, though both involve severe protein deficiency.

Both of these major protein deficiencies disorders, Marasmus and Kwashiorkor involve malnutrition and infection. Typically they can be easily differentiated on the following basis:a) Wasting associated Marasmus. b) Edema associated with of Kwashiorkor.

Infections are mainly thought to be due to the lack of antibodies to fight infections; resulting in:a) Feverb) Fluid imbalances and dysenteryc) Anemiad) Heart failure and possible death

RehabilitationWith nutrition intervention, recovery is possible, must slowly increase protein content in diet and the body will be unaccustomed to digesting and utilizing proteins.

How to Get Enough Protein in Your DietThe best sources of protein are meats, fish, eggs and dairy products. They have all the essential amino acids that your body needs. When a protein contains all the essential amino acids it is called a “complete’ protein. There are also some plants that are high in protein, like quinoa, legumes and nuts. In fact, quinoa is a complete protein.

In terms of health, since proteins can be viewed as a fundamental building block of the body, having the appropriate amount in your diet is naturally considered crucial to maintaining good health. If we don’t get enough from the diet, our health and body composition suffers. A basic nutrition recommend from the DRI (Dietary Reference Intake) for example is 0.36 g/lbs. (or 0.8 g/kg) of body weight. These are made with the assumptions that people are healthy, that the protein is mixed quality and the body will use protein efficiently.

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The typical amount for DRI is: 56 g/day for the average sedentary man. 46 g/day for the average sedentary woman.

You may ask yourself: What scientific research are these recommendations made from? The answer would be there have not been any defining experiments to demonstrate a specific level that needs to be consumed each day. If you’re a healthy person trying to stay healthy, then simply eating quality protein with most of your meals (along with nutritious plant foods) should bring your intake into an optimal range. The “right” amount of protein for any one individual depends on many factors, including activity levels, age, muscle mass, physique goals and current state of health. Therefore, you are going to have to start being the best judge of whether or not what you are eating and how much of it, is right for you.

What “Grams of Protein” Really MeansA common misunderstanding is to take the grams of a food as equivalent to its protein content, e.g., an 8 ounce serving of beef weighs 226 grams, but it only contains 61 grams of actual protein. A large egg weighs 46 grams, but it only contains 6 grams of protein. The grams of the macronutrient protein, not the grams of a protein containing food like meat or eggs, needs to be measured.

Protein is not just about quantity. It’s also about quality. At the risk of sounding repetitive, generally speaking, animal protein provides all the essential amino acids in the right ratio for us humans to make full use of them. This makes sense, since animal tissues are similar to our own tissues. If you’re eating animal products (like meat, fish, eggs, or dairy) every day, then you’re probably already doing pretty well, protein-wise.

If you don’t eat animal foods, then it is a bit more challenging to get all the protein and essential amino acids that your body needs. Most people probably don’t really need protein supplements, but they can be useful for athletes and bodybuilders. Protein can help you lose weight (and prevent you from gaining it in the first place).

Protein can be important when it comes to losing weight. Eating protein can stimulate the body to burn calories and boost your metabolic rate as well as reducing your appetite. This is well supported by science. Protein at around 25-30% of calories has been shown to boost metabolism by up to 80 to 100 calories per day, compared to lower protein diets.

Probably the most important contribution of protein to weight loss is its ability to reduce appetite and cause a spontaneous reduction in calorie intake. Protein can be more satiating than both fat and carbs. In a study in obese men, protein at 25% of calories increased feelings of fullness, reduced the desire for late-night snacking by half and reduced obsessive thoughts about food by 60%. In another study, women who increased protein intake to 30% of calories ended up eating 441 fewer calories per day. They also lost 11 pounds in 12 weeks, just by adding more protein to their diet.

In one study, just a modest increase in protein from 15% of calories to 18% of calories reduced the amount of fat people regained after weight loss by 50%. A high protein intake also helps to build and preserve muscle mass (see below), which burns a small amount of calories around the clock. By eating more protein, you will make it much easier to stick to whichever weight loss diet (be it high-carb, low-carb or something in between) you choose to follow. According to

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these studies, a protein intake around 30% of calories may be optimal for weight loss. This amounts to 150 grams per day for someone on a 2,000 calorie diet. You can calculate it by multiplying your calorie intake by 0.075.

The Protein PackageSome high-protein foods are healthier than others because of what comes along with the protein: healthy fats or harmful ones and beneficial fiber It’s this protein package that’s likely to make a difference for health.

I went to many web sites and from Conventional Dietitians-Nutritionist you get this advice:

For example, a 6-ounce broiled porterhouse steak is a great source of protein—about 40 grams worth and but it delivers about 12 grams of saturated fat. For someone who eats a 2,000 calorie per day diet, that’s more than 60 percent of the recommended daily intake for saturated fat. A 6-ounce ham steak has only about 2.5g of saturated fat, but it’s loaded with sodium—2,000 mg worth, or about 500 mg more than the daily sodium max. …so try lentils… it has virtually no saturated fat or sodium.

First of all, as we know and I will keep repeating, saturated fat is NOT bad for you. On the contrary, it is extremely beneficial to human health. And sodium is NOT bad for you. On the contrary, it is essential for good health. Who decided on the “max” limit anyway? Please note that meat will not contain just isolated sodium chloride, but all of the trance minerals, unlike the salt shaker at your favorite restaurant. If the only reason an idiot dietitian can find to advise you not to eat red meat is the advice above, then they are… idiots! Chances are they have never examined the extensive literature on the health benefits of various ‘vilified’ foods but are blindly accepting the unsubstantiated, or even false myths that are replete in most textbooks on the subject of Nutrition. Lentils are fine, but without any fats or salts they will be a little bland to many people’s palates; trust me, most will want to add other things to those lentils!

Also note: There are 5 brain nutrients found only in meat, fish and eggs (not plants). They are: 1) Vitamin B12, 2) Creatine, 3) Vitamin D3, 4) Carnosine and 5) Docosahexaenoic Acid (DHA). Thus it would appear we were not exactly meant to be herbivores.

More Protein Can Help You Gain Muscle and StrengthMuscle tissues in the body are made largely of protein. The most abundant type of muscle in the human body is skeletal muscle (~40% of body mass).This is the muscle that is attached to bone of the skeleton and is for body movement. Cardiac muscle is found in the heart and smooth muscle is located in organs such as the stomach and intestines, and lines many blood and lymphatic vessels in the body.

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Figure 12. Examples of the three different types of muscle tissue in the human body: Cardiac (in the heart); Skeletal (attached to bones); and Smooth (lining internal organs and vessels). Regardless of the location or function of the various muscle tissue in the body, it is primarily made up of two contractile proteins called myosin and actin.

Protein and Amino Acids in the Diet and SupplementationsAs with most tissues in the body, muscles are dynamic and are constantly being broken down and rebuilt. To gain muscle, the body must be synthesizing more muscle protein than it is breaking down. In other words, there needs to be a net positive protein balance (often called nitrogen balance, because protein is high in nitrogen) in the body. For this reason, people who want a lot of muscle will need to eat a greater amount of protein (and lifting heavy things would also increase muscle mass). It is well documented that a higher protein intake helps build muscle and strength. Also, people who want to hold on to muscle that they’ve already built may need to increase their protein intake when losing body fat, because a high protein intake can help prevent the muscle loss that usually occurs when dieting.

When it comes to muscle mass, the studies are usually not looking at % of calories, but daily grams of protein per unit of body weight (kilograms or pounds). A common recommendation for gaining muscle is 1 gram of protein per pound of body weight, or 2.2 grams of protein per kg. Numerous studies have tried to determine the optimal amount of protein for muscle gain and many of them have reached different conclusions. Some studies show that over 0.8 grams per pound has no benefit, while others show that intakes slightly higher than 1 gram of protein per pound is best.

If you’re carrying a lot of body fat, then it is a good idea to use either your lean mass or your goal weight, instead of total body weight, because it’s mostly your lean mass that determines the amount of protein you need.

Level of Activity and Age can Alter Protein NeedsDisregarding muscle mass and physique goals, people who are physically active do need more protein than people who are sedentary.

If you have a physically demanding job, you walk a lot, run, swim or do any sort of exercise, then you need more protein. Endurance athletes also need quite a bit of protein, about 0.5 to 0.65 g/lbs of bodyweight.

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Elderly people also need significantly more protein, up to 50% higher than the DRI, or about 0.45 to 0.6 g/ lbs. This can help prevent osteoporosis and sarcopenia (reduction in muscle mass), both significant problems in the elderly. People who are recovering from injuries may also need more protein.

Does Protein Have any Negative Health Effects?Protein has been unfairly blamed for a number of health problems. It has been said that a high protein diet can cause kidney damage and osteoporosis. However, none of this is supported by science. Although protein restriction is helpful for people with pre-existing kidney problems, protein has never been shown to cause kidney damage in healthy people. In fact, a higher protein intake has been shown to lower blood pressure and help fight diabetes, which are two of the main risk factors for kidney disease.

If protein really does have some detrimental effect on kidney function (which has never been proven), it is outweighed by the positive effects on these risk factors. Protein has also been associated with osteoporosis, however the studies actually show that protein can help prevent osteoporosis. Overall, there is no evidence that a reasonably high protein intake has any adverse effects in healthy people trying to stay healthy.

Protein and Chronic Diseases: Proteins in food and the environment are responsible for most food allergies, which are overreactions of the immune system. Beyond that, relatively little evidence has been gathered regarding the effect of the amount of dietary protein on the development of chronic diseases in healthy people.

There is little evidence of normal or excess protein consumption causing heart disease, although it is routinely stated that this is one of the risks of eating protein, especially protein derived from animal sources, and particularly red meat. However, if we already know that all proteins are made of amino acids and that is what they body breaks them down into, what would the sources of these identical molecules matter.

A common claim is that it may not be the high animal protein intake per se, but more so the high saturated fat intake as a consequence. This is presumably where the suggestion to ‘eat lean meat’ comes from. At the risk of sounding extremely repetitive, this nefarious link is again a complete fairy tale. Literally, this premise is invalid, as it is based on the faulty and essentially discredited studies Dr. Ansel Keys in the late 1950’s. This thoroughly unscientific belief system that links diets rich in saturated fats to heart disease has been shamelessly promoted for over 50 years, despite the fact that it is simply not true!

Eating burnt meat or burnt anything is not a good idea, nor is it good for your health! The Browning Effect is a chemical reaction between amino acids and reducing sugars that gives browned foods their desirable flavor. Seared steaks, pan-fried dumplings, breads, and many other foods make use of the effect. At higher temperatures, caramelization and subsequently pyrolysis become more pronounced. And a carcinogen called acrylamide can be formed. You do not want to eat known carcinogens, because they can casue cancer.

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In terms of excess protein consumption, it is possible that Homocysteine levels may increase the risk for heart disease but that arginine may protect against cardiac risk. Excessive glutamate may stimulate appetite and act as an excitotoxin to neurons in the brain, although levels found in normal animal products would not contain abnormally high amounts.

Adult Bone Loss (Osteoporosis) – it may be that high protein intake associated with increased calcium excretion, but inadequate protein intake is deleterious to bone health.

Kidney Stress: A very high protein intake increases the work of the kidneys, since deamination releases NH3 which is converted to urea by the liver, filtered by the kidneys and excreted in urine as a nitrogenous waste product.

The body cannot store protein; therefore, extra protein is converted to fat (see amino acid metabolism section).

Protein and Amino Acid SupplementsProtein Powders have not been found to improve athletic performance.a. Whey protein is a waste product of cheese manufacturing.b. Purified protein preparations increase the work of the kidneys.

Amino Acid Supplements may not beneficial if taken in isolation, without other components.a. Branched-chain amino acids provide little fuel and may be toxic to the brain in isolation, for example glutamate and aspartate.b. Lysine appears safe in certain doses. c. Tryptophan has been used experimentally for sleep and pain.

The Disorder of Phenylketonuria Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder caused by the extremely low levels or absence the enzyme phenylalanine hydroxylase (PAH), which converts the essential amino acid Phenylalanine (Phe) into Tyrosine (Tyr).

Normally, the PAH enzyme breaks down any excess phenylalanine (from all of its various sources in the diet) in the body. If you have PKU, however, the phenylalanine cannot be broken down and the excess can build up in the blood and brain to toxic levels, affecting brain development and function.

Untreated PKU can lead to intellectual disability, seizures, and other serious medical problems. The best proven treatment for classical PKU patients is a strict phenylalanine-restricted diet supplemented by a medical formula containing amino acids and other nutrients

This disorder is rare, but when identified early in life is very easy to treat. People who are diagnosed early and maintain a strict diet can have a normal life span with normal mental development, as long as the regulated diet is maintained for life.

Note: The artificial sweetener aspartame can act as poisons for people with phenylketonuria, one reason being the high levels of phenylalanine liberated from foods that contain aspartame.

It has been shown that ingesting aspartame, especially along with carbohydrates, can lead to excess levels of phenylalanine in the brain even in persons who do not have PKU. This is not just

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a theory; large amounts of aspartame over a long period of time produce excessive levels of phenylalanine in the blood in those who do not have PKU

So what exactly is Aspartame anyway?You may do a little research and find that the artificial sweetener Aspartame (which goes by brand name of “NutraSweet” or “Equal’) is made up of two amino acids: Phenylalanine (Phe) and Alanine (Ala). By default, some may want to persuade others that since aspartame is made by two amino acids that you usually eat anyway, it is therefore perfectly healthy and safe for you to consume in your food.

Let’s look a little closer! These two amino acids are synthetically bound together (i.e., ‘in a lab’) by creating weak methyl ester bonds between Phenylalanine and Alanine. When aspartame is heated above 86oF (30oC), this weak ester bond break and liberates free methanol. Methanol (wood alcohol) is a deadly poison. What is body temperature, by the way? It’s about 98.6oF (36.8oC), this means that your body heat is enough to generate methanol from whatever food item aspartame may be added to, especially your favorite diet soda. This can also occur when the product containing aspartame is stored above this temperature or heated (e.g. “foods" like Jello).

As discussed in class, once in our bodies, methanol gets converted by alcohol dehydrogenase to formaldehyde – found in embalming fluid, it is a deadly neurotoxin. The recommend Environmental Protection Agency (EPA) limit is 7.8mg/day A one-liter aspartame-sweetened beverage contains about 56mg.

Symptoms from methanol poisoning include serious vision problems, headaches, ear buzzing, dizziness, nausea, gastrointestinal disturbances, weakness, vertigo, chills, memory lapses, numbness and shooting pains in the extremities, behavioral disturbances, and neuritis. Formaldehyde is a known carcinogen, causes retinal damage, interferes with DNA replication and causes birth defects. The story of Aspartame does not stop at Methanol and Formaldehyde!

Aspartic Acid Dr. Russell L. Blaylock, Neurosurgeon at the Medical University of Mississippi, has published a book detailing the damage caused by the excessive ingestion of aspartic acid from aspartame. Citing almost 500 scientific references, he shows how excess free excitatory amino acids such as aspartic acid and glutamic acid (= 99% monosodium glutamate or MSG) in our food supply are causing serious chronic neurological disorders and a myriad of other acute symptoms.

How Aspartate (and Glutamate) Cause DamageAs we know, Aspartate and glutamate are amino acids and they also act as neurotransmitters in the brain. They are both ‘excitatory’ neurotransmitters that trigger other neurons into action. Thus, too much aspartate or glutamate in the brain kills certain neurons by allowing too much calcium influx. It triggers excessive free radicals, which kill the cells. This neural damage is referred to as "excitotoxins because they over "excite" or stimulate the neural cells to death.

Shortly after ingesting aspartame or products with free glutamic acid (glutamate precursor), the excess aspartate and glutamate in the blood plasma leads to a high level of those neurotransmitters in certain areas of the brain – The protective blood brain barrier (BBB)

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normally shields the brain from toxins such as excess glutamate and aspartate, however: 1) it’s not fully developed children; 2) the hypothalamus is not fully protected by it; 3) it can be damaged by chronic and acute conditions; and 4) allows seepage of excess glutamate and aspartate into the brain even when intact.

The excess glutamate and aspartate slowly begin to destroy neurons. The large majority (at least 75 %) of neural cells in a particular area of the brain are killed before any clinical symptoms of a chronic illness are noticed. A few of the many chronic illnesses that have been shown to be contributed to by long-term exposure to excitatory amino acid damage include:

Multiple Sclerosis (MS) Amyotrophic Lateral Sclerosis (ALS) Hypoglycemia Parkinson's diseaseMemory loss Hormonal problems Epilepsy Dementia/Brain lesionsAlzheimer's disease Neuroendocrine disorders

It may be that excessive buildup of phenylalanine in the brain can cause schizophrenia or make one more susceptible to seizures. Therefore, long-term, excessive use of aspartame may provide a boost to sales of serotonin reuptake inhibitors such as Prozac and drugs to control schizophrenia and seizures. A good solution to any of these possible health problems is to stop ingesting toxins and replace them in your diet with organic whole foods. This way you won’t have to be on any medications and will feel healthy, vibrant and alive.