Please be patient. This is a work in progress.
IMPORTANT: The information on this site should never be used to self medicate or to self diagnose. Always contact your health care provider before using any kind of supplementation or making any extreme change in diet.
What exactly is protein?
Let’s start with amino acids. Most of us have heard of amino acids but probably aren’t all that sure how they work to build the most powerful nutrient in our bodies.
In our world there are approximately 500 amino acids which have been identified. They are classified both by their structure and by their pH levels. They are also classified by their ability to build proteins:
- proteinogenic or standard are used to build proteins
- non-proteinogenic or non-standard.
There are 22 standard amino acids which are called proteinogenic. These amino acids are used to create proteins within the human body. The adult body can create 14 amino acids without getting them from food. The other 8 have to be eaten every day. These 8 are called the essential amino acids because it is essential that we eat them.
More than these 8 amino acids become essential for children because as we grow we need more of the amino acids cysteine, taurine, tyrosine and arginine than the body produces on its own so the rest has to be consumed in the diet.
The 8 essential amino acids we need to consume as adults are collected from dietary protein – protein that we eat. Our digestive system breaks down protein into its amino acid building blocks like blocks of lego so that they can be transferred through the intestinal wall and rebuilt into proteins that are needed by the human body to build & repair bones, muscles and tissue. They are used to create the enzymes that power many chemical reactions in the body and make up blood cells. These 22 building blocks are responsible for the creation of at least 10,000 different types of proteins in the human body.
This page is about protein so the amino acids discussed here will be the ones associated with protein it is worthwhile noting that many of the non-protein amino acids are of equal importance to our bodies and that many of the proteins that are used in building amino acids also act independently as non-proteinogenic amino acids. Both independent protein building amino acids and non-protein amino acids are involved in the proper functioning of such things as the neurotransmitters in our brains, in our blood, our DNA and in cell signaling.
The 22 amino acids are encoded with genetic coding from our genes which gives them instructions on what they can be used for when they combine in millions of different ways to form millions of proteins in our bodies.
When protein from food is eaten it is attached to all sorts of other nutrients and therefore needs to be broken down in the stomach by hydrochloric acid and an enzyme called pepsin. It is broken down into smaller units called polypeptide chains or into individual proteins which can more easily be broken down into individual amino acids. In the digestive tract they are then further broken down into single amino acids.
Once the amino acids have transferred through the intestinal wall into the body the amino acids are reconstructed into peptides which are short chains of molecules and or long chains of molecules; polypeptides or proteins. Peptides are used to build polypeptides. From here the proteins are used to build our bodies.
The following are the 22 amino acids:
Histidine acts as a proton shuttle. Helps to stabalize oxygen and carbon oxygen levels in haemoglobin.
Isoleucine is used in the citric acid cycle for oxidation or used in gluconeogenesis to convert protein to glucose. Isoleucine needs the vitamin biotin to be used.
Leucine is utilised in the liver, adipose tissue and muscle tissue. In the latter two it forms sterols. In muscles it stimulates the creation of muscles and protects them. It also regulates cell growth. Excess leucine can be toxic.
Lysine is used to produce acetyl-CoA an important element in the Citric Acid Cycle for energy production. Derivative of lysine called allysine is used to produce collagen and elastin.
Methionine assists in the biosynthesis of several amino acids and phospholipids. S-adenosyl methionine or SAM is needed for cell growth and repair and is also used in the creation of several hormones and neurotransmitters. SAM is a derivative of Methionine.
Phenylalanine is a precursor to the amino acid tyrosine; the signalling molecules dopamine, norepinephrine and epinephrine and the skin pigment molecule melanin. It has pain controlling and antidepressant effects. In large quantities it interferes with the production of seratonin.
Threonine is converted to pyruvate (pyruvic acid )and is therefore indirectly used to produce acetyl-CoA for use in the citric acid cycle for energy production. Pyruvate is also used in glucogneogenesis to convert proteins to glucose as a source of energy and is used to produce the amino acids glycine and alanine.
Tryptophan is used to build proteins and acts as a precursor for creating the neurotransmitter serotonin and the vitamin niacin. Intestinal problems such as fructose malabsorption and lactose intolerance lead to poor absorption of tryptophan in the intestines.
Valine Is synthesized starting with pyruvic acid. Promotes muscle growth and tissue repair. A precursor in helping the body to use penicillin.
Alanine is a non essential amino acid produced by the body. It is the second most frequently occuring amino acid next to leucine in protein synthesis. It is involved in glycolysis, the metabolic pathway which releases adenosine triphosphate which is needed for energy in the body. It is also involved in gluconeogenesis, the altering of proteins into glucose for use by the body for energy and it is used in the citric acid cycle which once again generates energy in our bodies.
Arginine is a conditionally essential amino acid. Arginine is conditional as an essential amino acid depending on certain conditions. Preterm babies are not able to synthesis arginine. Surgery, trauma, systemic inflammation and burns all require more arginine. In these cases it must be taken supplementally. Arginine is important for cell division, wound healing, the removal of ammonia from our bodies, immunity and the release of hormones. It is used in the production of nitric oxide which plays a key role in acting as a messenger in our bodies. One action is to signal the muscles to relax, consequently increasing blood flow thus decreasing blood pressure. Arginine also increases the healing time of damaged tissues.
Asparagine is a nonessential amino acid synthesised by the body is important in the synthesis of ammonia. The adding of the molecule N-actylglucosamine to asparagine is important to protein structure and function.
Aspartic Acid is a nonessential amino acid that is a precursor for several other amino acids: methionine, threonine, isoleucine and lysine. Aspartate participates in the the metabolic pathway gluconeogenesis. It also donates a nitrogen atom in the creation of a precursor to the purine basis. Purines adenine and guanine form the basis of half of our DNA and RNA and purines play a role in various metabolic pathways. Aspartate also acts as neurotransmitter in stimulating receptors.
Cysteine is a conditional essential amino acid. It can be synthesized in our bodies but sometimes needs to be taken in our diets or supplementally. The very young and the very old often have trouble metabolising this amino acid. A thiol group, sulfur containing compounds (think garlic) attach themselves to cysteine. As part of a thiol group cysteine has a large number of biological functions.
a. It is a precursor to the antioxidant called glutathione.
b. It acts as a precursor to iron-sulfur proteins.
c. It binds to metal ions such as zinc, copper, iron in cytochrome P450, and nickel. It also binds to heavy metals such as mercury lead and cadmium.
d. It plays several roles in protein structure such as the translation of RNA in producing proteins, the stabilising of the folding of protein molecules and the cross linking of proteins. Cystein is known to act as an antidote for the negative effects of alcohol including liver damage and hangover. Actetaldehyde is the by product of alcohol and FRUCTOSE metabolism. Cysteine supports the metabolizing o acetaldehyde into the harmless acetic acid.
Glutamic Acid is a non essential amino acid. The anions (negatively charged atoms) and salts of glutamic acid are called glutamates. Glutamate is a neurotransmitter that is important for learning and memory. This is the amino acid that produces the fifth taste called umami so now we have salt, sweet, bitter, sour and umami. Monosodium glutamate is a salt derivative of glutamic acid but is considered to be associated with many health problems. Glutamate is key in the metabolic processes within the cell.
Glutamin is a non-essential amino acid. It is involved in the synthesis of proteins as a proteinogenic amino acid. (An amino acid used to build proteins)
a. It produces ammonium which regulates the acid base in the kidney and it is a non toxic transporter of ammonium in the blood.
b. It is used for cellular energy along with glucose.
c. It donates nitrogen atoms for cell respiration and it donates carbon to the citric acid cycle.
Glycine is a non essential amino acid and is both a water lover and a water hater; hydrophilic and hydrophobic. It is synthesized by the amino acid serine. Provides a subunit for all purines in our DNA. In the spinal cord, brainstem and retina and other areas of the central nervous system glycine acts as an inhibitory neurotransmitter.
Ornithine is a non essential amino acid and an alpha amino acid which is not proteinogenic. It plays a role in the urea cycle ( the cycle that produces urea from ammonia). The urea cycle is also called the ornithine cycle. Excess nitrogen is disposed of through this cycle. The urea cycle is also used to biosynthesis the semi essential protein arginine which is one of the most important proteins in DNA synthesis.
Proline is an alpha amino acid that means that it is one of the twenty DNA encoded amino acids and is also a non essential amino acid. It is derived from glutamate. It is involved in DNA and RNA structure.
Selenocysteine is involved largely with proteins that are involved in antioxidant missions. It is present in several enzymes. There are 25 proteins in humans that contain this amino acid.
Serine is a proteinogenic amino acid (used to build proteins) which is semi essential. Its functions include:
a. The synthesis of DNA and RNA.
b. Acts as a precursor to the synthesis of several amino acids such as glycine and cysteine.
c. Acts as a precursor to metabolites such as sphingolipids (type of fat) and folate (vitamin B9).
d. Plays a role in activating many enzymes.
e. It is involved in serving as neurotransmitters and gliotransmitters (neuronal communicators in the brain).
Tyrosine is a proteinogenic semi nonessential amino acid. It is synthesized from the amino acid phenylalanine. Tyrosine is a precursor to neurotransmitters and increases blood neurotransmitter levels without affecting mood. It is shown to be effective in times of stress.
Although the number of proteins in the human body is in the millions there is a simple breakdown to give us an idea of what proteins do in our bodies. This list can be found at: http://en.wikipedia.org/wiki/List_of_proteins
The following is a simplified breakdown of the information provided there.
Proteins fall into 3 basic categories:
Proteins found as part of complex units
1. FIBROUS PROTEINS
Fibrous proteins have two basic categories which are Cytoskeletal proteins and Extracellular matrix proteins.
Cytoskeletal proteins are involved in the structure or scaffolding of a cell’s cytoplasm. This scaffolding is present in all cells and plays an important role in both cell division and in transport within the cell. The three main kinds of cytoskeletal filaments or structures are microfilaments, intermediate filaments and microtubules. Microfilaments create movement. Intermediate filaments maintain cell shape and organize cell structure. Microtubules maintain flagella and cilia within the cell and act as substrates to the transcription of RNA and the replication of DNA. Actin, Arp2/3, Coronin, Dystrophin, FtsZ and Keratin are the most well known cytoskeletal proteins.
Extracellular Matrix Proteins – ECM ECM is the external matrix which supports the cell from without. Cell adhesion, cell to cell communication and cell differentiation are functions of the ECM. The interstitial matrix and the basement membrane are made up of two components of the ECM. The interstitial matrix is the space matrix between the cells and is filled with polysaccharides and fibrous proteins that act as compression buffers against too much stress placed on the matrix. The basement membrane form sheets of ECM to support the epithelial cells which line the surfaces of structures throughout our bodies. ECM provides support to cells, segregates tissues from one another and regulates communication between cells. It holds and or stores a large number of substances that stimulate cell growth. It is essential for growth, wound healing and development of fibrous material. Because of its activity in cell growth it is invaluable in the exploration of tumor invasion and the study of cancer metastasis. Collagen, Elastin, F-spondin, Pikachurin and Fibronectin are all Extracellular matrix proteins.
2. GLOBULAR PROTEINS
Globular proteins are spherical in shape and are water soluble so will dissolve into liquids unlike fibrous or membrane proteins.
Globular proteins can act as enzymes in certain reactions when the conditions are mild and are very specific.
They transmit messages for the regulation of biological processes in the form of hormones.
They transport other molecules through membranes as transporter units.
Globular proteins hold stocks of amino acids to be formed into proteins.
Globular proteins have several categories:
a. Plasma proteins
c. Cell adhesion proteins which include ion channels and synport/antiport proteins.
d. Hormones and growth factors
f. DNA binding proteins
g. Immune system proteins
h Nutrient storage transport
i. Chaperone proteins
a. Plasma Proteins
Plasma is a pale yellow liquid that holds blood cells in suspension. It contains dissolved proteins ( globular proteins). These are: Serum Amyloid P component and Serum albumin.
Coagulation factors are involved in the coagulation of blood to form clots that help repair damaged cells and prevent blood loss. Coagulation factor proteins include complement proteins C1 inhibitor and C3 convertase, Factor Vlll, Factor Xlll, Fibrin, Protein C, Protein S, Protein Z, Protein Z related protease inhibitor, Thrombin, Von Willebrand Factor.
Acute phase proteins This is a class of proteins that respond to inflammation by either increasing in numbers or decreasing in blood plasma. C-reactive protein is the most notable of these proteins.
Hemoproteins are involved in:
- Oxygen transport using the proteins haemoglobin, myoglobin, neuroglobin, cytoglobin and leghemoglobin.
- Catalysis using cytochrome P450s, cytochrome, c oxidase, ligninases, peroxidases.
- Electron transfer and transport using cytochrome a, cytochrome b and cytochrome c.
- Sensory information using FixL and oxygen sensor, soluble guanylyl cyclase and CooA and carbon monoxide sensor.
- Defense against foreign invaders such as certain bacteria using catalase proteins.
c. Cell adhesion
Cell adhesion occurs when a cell is bound to a surface such as a cell matrix or to another cell. It maintains multicellular structure; seals gaps between cells; links the cytoplasm of adjacent cells and relays signals or synapses in the nervous system.
Some of the most important proteins in this category are cadherin proteins, ependymin proteins, integrin proteins, integrin, NCAM and selectin proteins.
Ion channels are formed to provide routes for ion transport across membrane walls. They allow only certain sized ions with specific charges to pass through and they differ depending on their location. Most are only large enough to accommodate one or two atoms at a time. They are most prominent in the workings of the nervous system and are also used in biological processes such as rapid changes in cells transporting ions in the cardiac, skeletal, muscular, epithelial and pancreatic systems as well as T-cell activation. They are present as either a. ligand-gated ion channels which include nicotenic acetylcholine receptors and GABAa receptors and b. voltage-gated ion channels which include potassium, calcium and sodium channels.
Synport and antiport proteins are used to transport molecules across the plasma membrane.
The most prevalent or prominent of these is the glucose transporter or GLUT family of proteins that transfers glucose into the cells to be used for energy.
Hormones are chemicals in our bodies that regulate specific activities within our bodies. Activities such as digestion, sexual behaviours, growth and mood control are all controlled by hormones.
There are 45 hormones that are formed from proteins and more that are formed from monoamines ( amino acid group molecules).
As hormones these proteins affect our appetites; stimulate our thyroid glands; control our stress response; control our immune response, inflammation, electrolyte levels, heartbeat, water retention, blood pressure, blood calcium levels, pain levels, stomach muscle contractions, red blood cell production, insulin production and resistance, growth, cell production and specialization, melanin production, sleeping patterns, orgasm, activation of vitamin D, milk production and more.
The hormones that are monoamines act as neurotransmitters such as adrenaline, dopamine, serotonin and melatonin.
Receptors are proteins that receive instructions from external substances like hormones, neurotransmitters, drugs or toxins that direct the cell to do something. The signal might instruct the cell to divide, or to perform a job more specifically or to die (apoptosis) or it might instruct it to allow another substance into or out of the cell.
Receptors are located a. on the cell’s surface or membrane, b.on the cytoplasm which is right beneath the surface membrane and c. as nuclear receptors in the nucleus of the cell.
The chemical to which the receptor attaches is called a ligand. Each ligand has a specific code which connects to a specific receptor a little bit like a password connects to a specific website.
There are transmembrane receptors, intracellular receptors, enzyme receptors and ion channel receptors.
Transmembrane receptors receive information from ligands on the outside of the cell and transfer that information to the inside of the cell.
Intracellular receptors are found inside the cell in such places as the nucleus of the cell, the cytoplasm or the endoplasmic reticulum.
Ion channel receptors have already been discussed under ion channels above.
Enzyme receptors will be discussed with the part on enzymes.
f. Proteins and DNA
DNA and RNA are called nucleic acids which are one of the three macromolecules in human biology. The other two are carbohydrates and proteins. Nucleic acid is composed of three basic components: a 5-carbon sugar. a phosphate group and a nitrogen base. The sugar defines whether it is DNA or RNA. If the sugar is deoxyribose then it is DNA and if it is just ribose then it is RNA. The four nucleobases, nitrogen containing molecules that make up our DNA, are adenine, cytosine, guanine and thymine and in RNA they are adenine, cytosine, guanine and uracil.
The sequencing of these bases is the foundation of all the genetic instructions that go into how our bodies operate depending on how they are arranged within our DNA and carried out by our RNA.
Each cell in our body has a complete set of instructions which are organized in long molecular structures called chromosomes where chromatin proteins called histones organize the DNA for transcription by RNA.
RNA copies the genetic information from DNA into appropriate amino acid sequences to form specific proteins to fulfill specific tasks.
There are three main types of RNA. Messenger (mRNA) which carries the genetic sequence information from DNA to the ribosomes in the cell nucleus where the information is used by rRNA (ribosomal RNA) to create specific proteins. The third type is tRNA (transfer RNA) which decodes the mRNA. There are about fifteen other smaller classes of RNA which carry out various operations.
So it is here in the center of the cell that proteins are formed from the instructions from 4 different nucleobasis.
This is a great website that explains DNA sequencing.: http://www.sciencemuseum.org.uk/whoami/findoutmore/yourbody/whatdoyourcellsdo/howdocellsmakeproteins/howareproteinsmade.aspx
There are also four different structures that proteins define themselves by.
The primary structure is the one just discussed – amino acid sequencing.
The secondary structure involves folding patterns known as alpha helices and beta sheets. Most proteins have many helices and sheets. These helices and sheets stabilize the protein so that it is not approached by inappropriate molecules within the cell.
The third or tertiary structure is the assembling of formations and folds into a single chain of amino acids called polypeptides. This clearly defines the protein for its role within the cell and within the body.
The fourth structure is found in macromolecules which have multiple polypeptide chains or subunits which are further defined for more advanced functions.
During the folding process the unfolded proteins are guided into their proper folding structures by ‘chaperone proteins’ which prevent unintended associations with other molecules that they were not intended to associate with.
From here proteins bind to specific molecules to complete specific tasks. Specifically shaped proteins interact with certain molecules.
Proteins that are similar in shape are thought of as families of proteins and usually have similar amino acid sequencing.
g. Immune System Proteins
The immune system operates on several levels. First antigens (the bad guys) have to make it past the surface barriers.
If they make it past the surface barriers the innate immune system attempts to deal with them by producing things like inflammation or with complement cells that gang up on the invader and destroy it.
The last line of defense the adaptive immune response uses killer T cells, helper T cells and B cell. B cells are used to copy the information of the attacker, kills it and replicates its information to be used in the future for the body to destroy it should it return.
The immune system, as do all systems in our body, uses great numbers of proteins to accomplish its work. The following is a sample of what proteins are used to protect us from disease and illness.
Surface barriers: skin and respiratory tract; antimicrobial peptides such as beta- defensins. In saliva, tears and breast milk ; enzymes such as lysozyme and phospholipase A2 are antibacterials; in the stomach proteases defend against ingested pathogens.
Innate Immune system:
Cytokines produce inflammation. Cytokines include interleukins that communicate between white blood cells; chemokines which cause bacteria such as e-coli to loose there sense of direction; and interferons that produce anti-viral effects that shut down processes in the host cell that allow the virus to continue. Cytokines bring in immune cells and promote healing after the pathogens have been removed.
Complement system: Over 20 different proteins are involved in the ‘biochemical cascade’ that attacks foreign cells on their surfaces as they complement antibodies in the killing of pathogens. This system activates a rapid killing response by attracting immune cells that coat the surface of the pathogen and mark it for destruction. The complement proteins can also kill the pathogen cells directly by disrupting their plasma membrane.
Cellular barriers: Phagocytes such as macrophages, neutrophils and dendritic cells make use of enzymes to destroy pathogens.
Adaptive Immune System Killer T cells: the protein perforin forms pores in the target cell’s plasma membrane to allow the protein granulysin and other toxins to enter and induce apoptosis (cell death). This is particularly important in destroying cells that have been invaded by cancer.
Helper T cells: T cells that release proteins called cytokines which increase macrophagic activity of the killer T cells. The protein CD154 expressed on the T cell’s surface stimulates signals to produce antibodies.
B lymphocytes and antibodies: B cells identify pathogens take them up and break them into peptides. These peptides are recognized by helper T cells which release proteins called lympokines that activate the B cell to divide and secrete millions of copies of the antibody that recognizes this antigen. The antigen is marked by these antibodies for destruction not only in the present but for years to come should it ever enter the body again.
The protein complex IgG is an antibody that is transferred from the mother so that the baby will be protected against all the diseases that the mother has been protected against with antibodies until the baby can develop its own immune reponses.
h. Nutrient Storage
Proteins Ferritin is a storage protein. It stores iron so that it can be released as needed. Ferritin keeps iron from becoming readily depleted and it keeps it from running free in our bodies. If iron were allowed to run free it would be highly toxic to us.
i. Chaperone Proteins
Chaperone proteins are involved in folding of polypeptides into their functional shape so that they are ready to go to work as proteins in whatever responsibility they are intended for. They are also used in the assembling or disassembling of other macromolecular structures such as nucleosomes (basic DNA packaging).
All the metabolic processes that sustain life in our bodies are conducted with the use of enzymes. Enzymes are large molecules that are created to produce energy. Most enzymes are designed to be highly selective in what they do. However, there are some that have broad range selectivity. These are thought to have a place in how we were able to evolve in a relatively controlled way throughout our evolution.
Each molecule is designed to connect with a specific substrate. A substrate is any substance that needs to be altered to perform another activity. The end result is called a product. For instance a substrate would be starch from a piece of bread. Enzymes are used to breakdown the starch, the substrate, into glucose molecules, the product.
Sometimes there are several reactions as substrate leads to product; product becomes substrate for another reaction and the new substrate is transformed into yet another product and so on. This is called a metabolic pathway. Enzymes are usually proteins although some ribosomes called ribozymes (which are also built from proteins) also act as enzymes. Enzymes are responsible for:
- signal transduction
- cell regulation
- movement using adenosine triphosphate to generate muscle contraction
- moving substances around the inside of the cell’s infrastructure.
- involvement in active transport, moving substances through the ion pump from one side of the cell membrane to the other.
- involved in the digestion of food in the digestive system. They break down large molecules such as carbohydrates, proteins and lipids into smaller ones so that they can be absorbed through the intestinal wall.
- They also play a role in disease. Viruses also contain enzymes which they use to infect and destroy healthy cells.
How Do Enzymes Work?
Enzymes work by lowering the amount of energy being produced by the substrate so that it’s molecular information can be worked on to produce a new substance so that it is transformed into a new product to be used by the cell.
An overly simplified example of this would be the off ramp from a high speed highway. The highway would be the substrate. The off ramp would be the enzyme and the road that the off ramp leads to would be the product. The off ramp has lowered the energy (speed) in order for the car to go onto a different road and move in a different direction to get different results. Each off ramp is marked to attain different results. Without the ramps the only way off the ramp would be to drive the car down over the embankment. It would take forever to get off the damned highway.
Enzymatic activity speeds up the transformation process by millions of times. Enzymes can catalyze several million reactions in a second. The removal of a carbon from a molecule without an enzyme could take over 100 million years just waiting for it to rot or degrade. (Kind of like waiting for plastic products to breakdown in a garbage dump.) But, add an enzyme and voila – instantaneous.
Enzymes often use non-protein molecules to assist them in their activities. These molecules are called cofactors. Cofactors can be either organic such as flavin from Vitamin B2 (riboflavin) or they can be inorganic as in minerals such as zinc. Organic cofactors can either be bound to the enzyme as a prosthetic or act as coenzymes which are released from the sight after the reaction in order to transfer chemicals between enzymes.
Protein inhibitors are molecules that control the development of proteins and protein structures in our bodies. Protease inhibitors can be found in soy, seeds, legumes, potatoes, eggs and cereals.
Too little protein and the body starts to use its own muscle protein to breakdown into amino acids to recycle into proteins for the body to use for more vital needs such as the respiratory system or for blood cells. This is why people as we get older need to make sure we get enough protein. Often seniors do not eat as much and consequently lack protein.
Too much protein and the body has to get rid of it. It is converted to amino acids in the liver. The liver converts excess amino acids to other usable molecules but in the process ammonia is produced. (If the aromatic amino acids such as tryptophan and phenylalanine build up too much they become toxic and will damage the liver.) The ammonia is converted to urea and excreted by the kidneys. Too much urea creates excess stress on the kidneys. If this happens over prolonged periods of time kidney disease will probably result.
3. PROTEINS AS PART OF COMPLEX UNITS
Proteins are also involved in several complex systems some of which have been touched on above.
Some of the most important of these are:
One complex unit is the nucleosome which is used to package DNA. Histone protein cores are what DNA is wrapped around so that 2 meters of DNA can fit into the nucleus of the cell. Imagine – 2 meters into every cell in our bodies. Ribonucleoprotein: The ribonucleoprotein is a protein that contains RNA. It combines ribonucleic acid and protein together.
Signal Recognition Particle:
This is a ribonucleoprotein that targets specific proteins in the endoplasmic reticulum in the cell and directs them to the right receptor.
Large and complex group of molecules in the cell nucleus which contain small ribonucleic particles which are protein complexes and other proteins. They are involved in splicing DNA and RNA so that their information can be present on distinct segments of their molecules.
The governments in both the U.S. and Canada tell us that adult women should get 46 grams of protein per day. Adult men need to consume 56 grams of protein per day. The Institute of Medicine recommends .8 grams per kilogram or 8 grams for every 20 pounds of body weight of protein. ￼
http://www.medicalnewstoday.com/articles/180858.php http://en.wikipedia.org/wiki/Protein_complex http://en.wikipedia.org/wiki/Protein_moonlighting http://www.northwestern.edu/newscenter/stories/2011/10/proteomics-http://ghr.nlm.nih.gov/glossary=peptide http://en.wikipedia.org/wiki/List_of_human_hormones http://en.wikipedia.org/wiki/Protein_in_nutrition http://en.wikipedia.org/wiki/Enzyme