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Protein And Amino Acids

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The Roles Of Protein

Building materialsEnzymes HormonesRegulators of fluid and electrolyte

balanceAcid-base regulatorsTransportersAntibodies

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As Building Materials

Proteins serve as the building blocks of most body structures.

Bone and teeth contain a protein matrix.

Protein collagen is the material of ligaments and tendons.

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As Enzymes

Enzymes are proteins that facilitate chemical reactions without being changed in the process; Protein catalyst.

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As Hormones

Some hormones are proteins.Growth hormoneInsulin and glucagonThyroxin.Calcitonin and parathyroidAntidiuretic hormone

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As Regulators Of Fluid And Electrolytes Balance

The body’s fluids are contained inside the blood vessels (intravascular), within the cells (intracellular), and between the cells (intercellular).

Fluids flow freely between these compartments. Cells can’t move these fluids, instead they manufacture proteins.

Proteins help regulate the composition of body fluids, as well as their quantity. They maintain equilibrium in the surrounding fluids by moving molecules into and out of cells.

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As Acid-Base Regulators

Acids- compounds that release hydrogen ions.Bases- compounds that accept hydrogen ions.Buffers- compounds that help keep a solution’s acidity

or alkalinity constant.

Normal body processes continually produce acids and bases, which the blood carries to the kidneys and lungs for excretion.

Proteins act as buffers, maintaining the acid-base balance of the blood and body fluids.

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As Transporters

Proteins function as carriers for:

VitaminsMineralsLipidsOxygen

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As Antibodies

Proteins protect the body against disease.

Antibodies are giant protein molecules produced by the immune system designed to combat “foreign invaders”.

They combine with and inactivate the foreign invader thus protecting the body.

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Proteins And Amino Acids

Proteins- compounds composed of carbon, hydrogen, oxygen, and nitrogen atoms, arranged from amino acids linked in chains.

Amino acids- building blocks of proteins: Each contain an amino group (NH2), an acid group (COOH), a hydrogen atom (H), and a distinctive side group all attached to a central carbon atom (C).

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Amino Acids

There are 20 common amino acids which proteins are comprised of. 9 of them are essential, the remaining 11 are not.

* Note: essential means that the human body cannot make them. We must obtain them from our diet.

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Essential Versus Non-Essential

Essential Histidine Lysine Methionine Phenylalanine Threonine Tryptophan Leucine Isoleucine Valine

Non-essential Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic acid Glutamine Glycine Proline Serine Tyrosine

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ProteinsPeptide bonds are the bonds that link amino

acids together to form protein.

Dipeptide- two amino acids bonded together.

Tripeptide- three amino acids bonded together.

Polypeptide- many amino acids bonded together.

Condensation reactions create the bonds between amino acids.

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Digestion Of Proteins

In the stomach-Hydrochloric acid

Denatures the protein structureConverts pepsinogen to pepsin

PepsinCleaves proteins to smaller polypeptides and

free amino acids

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Digestion Of Proteins {continued}

In the small intestines-

EnteropeptidaseConverts pancreatic trypsinogen to

trypsin

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Digestion Of Proteins {continued}

TrypsinCleaves peptide bonds for specific amino acids

Converts pancreatic procarboxypepitases to carboxypeptidases

Converts pancreatic chymotrypsinogen to chymotrypsin

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Digestion Of Proteins {continued}

ChymotrypsinCleaves peptide bonds for specific amino acids

CarboxypeptidasesCleave amino acids from the acid end of

polypeptides

Elastase and collagenaseCleaves polypeptides into smaller polypeptides

into smaller polypeptides and tripeptides

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Digestion Of Proteins {continued}

AminopeptidaseCleaves amino acids from the amino

ends of small polypeptides

TripeptidaseCleaves tripeptides into dipeptides

and amino acids

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Absorption Of Amino Acids

Free amino acids and some di- and tripeptides which escaped digestion enter the bloodstream from the intestinal cells.

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Protein Quality

Can determine how well children grow and how well adults maintain health

Limiting amino acid- the essential amino acid found in the shortest supply relative to the amounts needed for protein synthesis in the body. The four most likely to be limiting: lysine, methionine, threonine, and tryptophan.

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Protein Quality {continued)

Complete protein- a dietary protein that contains all the essential amino acids in relatively the same amounts that human beings require.

Complementary proteins- two or more incomplete proteins whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other.

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Proteins In Foods

Meat, fish, poultry, and dairy products are the richest sources of protein.

Legumes and grain products contain moderate amounts of protein.

Vegetables and fruit provide little protein.

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Recommended Amounts Of Proteins

Protein should account for ~ 15% of total daily energy intake.

The RDA for adults is 0.8 grams per kilogram of body weight.

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Protein-Energy Malnutrition- PEM

PEM is a deficiency of both protein and energy. It is the world’s most widespread malnutrition problem, including kwashiorkor, marasmus, and a combination of both.

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Kwashiorkor

A form of PEM that results either from in-adequate protein intake or infections, however, with adequate calories. Usually acute in nature.

Due to the lack of protein and subsequently, fluid maintenance, faces and limbs become swollen with edema. They develop fatty livers which account for the swollen belly appearance.

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Marasmus

A form of PEM that results from a chronic deficiency of calories, or impaired absorption, of energy, vitamins, and minerals.

This is characterized by extreme loss of muscle and fat, wasted appearance.