1. Chapter 6 Protein and Amino Acids

2. Sources of Protein in the Diet
Protein deficiency is rare in the United States.
In the US, about two-thirds of dietary protein comes from meat, poultry, seafood, eggs and dairy products.
Most of the world relies on plant proteins from grains and vegetables.
As a country’s economy improves, the proportion of animal foods in the diet tends to increase.
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3. Sources of Protein in the Diet
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4. Sources of Protein in the Diet
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5. Animal versus Plant Protein
Animal products provide sources of protein, B vitamins and minerals such as iron, zinc and calcium.
However, animal products are low in fiber and can be high in fat.
Plant sources of protein are also a good source of B vitamins, iron, zinc, fiber and calcium, but in less absorbable forms.
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Amino Acids
Amino acids are the building blocks of protein.
Each amino acid contains a central carbon atom bound to a hydrogen atom, an amino group, an acid group and a side chain.
Essential amino acids cannot be synthesized by the human body in sufficient amounts to meet needs.
Essential amino acids must be included in the diet.
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7. Amino Acids and Protein Structure
Proteins: atoms of carbon, hydrogen, oxygen, and nitrogen—arranged as strands of amino acids.
Amino (a-MEEN-o) acids: building blocks of protein; each is a compound with an amine group at one end, an acid group at the other, and a distinctive side chain.
Amine (a-MEEN): group the nitrogen- containing portion of an amino acid.
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8. Amino Acids and Protein Structure
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9. Amino Acids and Protein Structure
Nine essential amino acids:
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Essential amino acids: amino acids that cannot be synthesized by the body or that cannot be synthesized in amounts sufficient to meet physiological need.
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11. Amino Acids and Protein Structure
Proteins are made of many different amino acid units hooked to each other.
A strand of protein is not straight; it is more like a tangled chain. The amino acids at different places along the stand are attracted to one another, and this attraction causes the strand to coil into a shape similar to that of a metal spring. This coil tangle has a globular structure.
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12. Amino Acids and Protein Structure
The differing shapes of proteins enable them to perform different tasks in the body.
Proteins may repel or attract water. (Charged amino acids are attracted to water, the neutral amino acids are repelled by water)
Some proteins contain minerals or vitamins.
Several proteins may gather to form a functional group.
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13. Amino Acids and Protein Structure
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Phenylketonuria
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15. Amino Acids and Protein Structure
Denaturation: the change in shape of a protein by heat, alcohol, acids, bases, salts of heavy metals, or other agents.
First step in the protein’s breakdown.
Useful to the body in digestion.
Stomach acid opens up the protein’s structure, allowing digestive enzymes to spilt peptide bonds.
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16. Amino Acids and Protein Structure
Cooking an egg denatures its proteins.
Cooking eggs liberates biotin and iron and helps in protein digestion
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17. Protein Digestion and Absorption
When a food protein is eaten, the digestive system breaks the protein down and delivers the separated amino acids to the body cells that put the amino acids together in the order necessary to produce needed proteins.
Protein digestion
Initiated in the stomach
Moves into the small intestine as single amino acids, or strands of two, three, or more amino acids.
Digestion continues until almost all pieces of protein are broken into dipeptides, tripeptides, and more free amino acids.
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18. Protein Digestion and Absorption
By the time proteins slip into the small intestine, they are already broken into different-sized pieces.
Some single amino acids and many strands of two, three, or more amino acids.
There are dipeptides, tripeptides, and longer chains.
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19. Protein Digestion and Absorption
Protein absorption
Absorption of amino acids takes place all along the small intestine.
The cells that line the small intestine capture dipeptides and tripeptides on their surface, split them into amino acids on the cell surfaces, absorb them, and then release them into the blood stream.
Amino acids are available to be taken up by any cell when they are circulating in the bloodstream.
The cells can then make proteins for their own use.
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20. Protein Digestion and Absorption
Nonessential amino acids can be manufactured by the body from fragments of other amino acids.
If essential amino acids are missing, protein building will halt.
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21. Protein Digestion and Absorption
Nonessential versus essential amino acids
Cells make protein strands from nonessential amino acids.
If essential amino acids are missing in the cell, the cells cannot complete the protein strand, and so protein building stops.
The cell cannot hold these partially completed proteins; therefore, they are dismantled and return into circulation, making them available to other cells.
If other cells do not soon pick up these amino acids and insert them into proteins, the liver will remove their amine groups for the kidney to excrete.
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22. Protein Digestion and Absorption
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Synthesizing Protein
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Synthesizing Protein
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Synthesizing Protein
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Synthesizing Protein
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27. Function of Protein in the Body
Protein is part of every living cell.
No living tissue can be built without protein.
Proteins account for about 20% of our body weight.
Proteins come in many forms and perform many vital functions (enzymes, antibodies, hormones, transport vehicles, oxygen carriers, tendons and ligaments, scars, the cores of bones and teeth, the filaments of hair, materials of nails).
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28. Function of Protein in the Body
Growth and maintenance
Building materials for growth and maintenance
Body structure
Regulatory rules
Enzyme
Hormones
Antibodies
Fluid balance
Acid-base balance
Transportation
Energy Production

29. Function of Protein in the Body
All enzymes are proteins, and are among the most important proteins because they are catalysts that help chemical reactions take place (Biological spark plug).
Enzyme Action Each enzyme facilitates a specific chemical reaction.
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30. Function of Protein in the Body
Hormones:
Hormones are similar to enzymes in the importance of their function,
they differ
Not all are made of protein,
They do not catalyze chemical reactions directly
Instead act as messengers that maintain a normal environment within the body.
chemical messengers.
Hormones are secreted by a variety of glands in the body in response to altered conditions.
Each affects one or more target tissues or organs and elicits specific responses to restore normal conditions.
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31. Function of Protein in the Body
Antibodies: large proteins of the blood and body fluids, produced by one type of immune cell in response to invasion of the body by unfamiliar molecules (mostly foreign proteins).
Antibodies inactivate the foreign substances and so protect the body.
Each antibody is uniquely designed to destroy a specific foreign antigen.
The foreign substances are called antigens.
One the body learn to make a particular antibody it never forgets and next time even it destroy the antigen even more rapidly (Immunity).
Malnutrition injures the immune system.
Often protein deficiency and immune incompetence appear together.
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32. Function of Protein in the Body
Fluid balance
Proteins help regulate the quantity of fluids in cell compartments to maintain fluid balance – necessary for life.
Too much, it ruptures.
Too little, it is unable to function.
Proteins attract water
Proteins cannot diffuse freely in and out of cells
The water-attracting protein stores inside the cells help the cells meet their fluid needs.
Proteins released into the blood (blood vessels) act in the same way in maintaining blood volume.
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33. Function of Protein in the Body
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34. Function of Protein in the Body
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35. Protein as a Source of Energy
Protein As Energy:
In the absence of adequate energy, the body will sacrifice protein to provide energy.
The amine group will be degraded, incorporated by the liver into urea, and sent to the kidneys for excretion in urine.
Urea (yoo-REE-uh): the principal nitrogen excretion product of metabolism, generated mostly by the removal of amine groups from unneeded amino acids or from those amino acids being sacrificed to a need for energy.
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36. Protein as a Source of Energy
Protein As Energy:
After the amine group is removed, the remaining carbon, hydrogen and oxygen will be used for immediate energy.
Protein sparing: a description of the effect of carbohydrate and fat, which, by being available to yield energy, allow amino acids to be used to build body proteins.
Excess amino acids are not stored by the body.
After removing the amine group, the excess is converted to glycogen or fat for energy storage.
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37. Protein as a Source of Energy
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Protein Deficiency
Protein-energy malnutrition (PEM) is a term that covers a range of protein deficiency conditions that may include only protein deficiency or protein deficiency plus energy deficiency.
Kwashiorkor is a pure protein deficiency.
Marasmus is an energy deficiency.
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39. Protein Deficiency
Kwashiorkor (the evil spirit that infects the first child when the second child is born ): a deficiency disease caused by inadequate protein in the presence of adequate food energy.
Symptoms
Edema : swelling of body tissue caused by leakage of fluid from the blood vessels, seen in (among other conditions) protein deficiency.
Apathy: no cry even for foods.
Skin and hair: Changes in skin pigment and hair color and texture (no protein pigment)
Fatty liver: (Lack of lipoproteins)
Failure to gain weight and grow
Loss of muscle mass
Anemia (Blood protein is not synthesis including hemoglobin)

40. Protein Deficiency
Marasmus (ma-RAZ-mus): an energy deficiency disease; starvation.
Symptoms: Same as kwashiorkor
Differences: Wizened little old person, just bone and skin
Dysentery (DISS-en-terry): an infection of the digestive tract that causes diarrhea..
Metabolism is slow so the temperature is subnormal.
Acquired immune deficiency syndrome (AIDS): an immune system disorder caused by the human immunodeficiency virus (HIV).
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41. Protein Deficiency Treatment:
Getting more calories and protein will correct kwashiorkor, if treatment is started early enough. However, children who have had this condition will never reach their full height and growth.
Prevention
To prevent kwashiorkor, diet must have enough carbohydrates, fat, and protein.
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42. Protein Deficiency In general PEM cases:
Cases are targeted easily by any infections (antibodies degraded to provide amino acids for other uses)
Muscles are wasted, including heart muscles
Epidemiology: prevalent in Africa, Central America, South America, and Asia.
Cases are reported in Indian reservations and in the inner cities and impoverished rural areas of the United States.
PEM is prevalent in unnourished patients including:
Those with anorexia nervosa, AIDS, cancer.

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Protein Excess
Elevated protein intakes over long periods of time can results in:
Hydration and kidney function issues
Bone health issues
Increased risk of heart disease and cancer
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44. Protein Excess
The problems of protein excess can be found in developed countries.
Possible to overload the liver and kidneys.
Can promote calcium excretion.
Excess protein can be converted to energy and stored as body fat.
Excess protein may also create an increased demand for vitamin B6 in the diet, so that the body can utilize the protein.
Since protein-rich foods are often high in saturated fat, cholesterol, and calories, so can increase the risk of obesity.
The higher a person's intake of animal-protein sources, the more likely to consume less fruits, vegetables, and grains, so might other nutrient deficiency happen.
No apparent benefit to consuming too much protein when caloric intake is adequate.
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45. Protein and Health
Foods that supply protein in abundance are shown here in the Milk Group and the Meat & Beans Group of the MyPyramid Food Guide (top two photos).
Servings of foods from the Vegetable Group and the Grains Group can also contribute protein to the diet (bottom two photos).
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46. Protein contributed by food groups in the average U.S. diet
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Protein Allergies
Food allergies are triggered when a protein from the diet is absorbed without being completely digested.
Protein from milk, eggs, nuts, wheat, soy, fish and shellfish and peanuts are common sources of food allergies.
A rapid, severe allergic reaction is called anaphylaxis.
People with GI disease are prone to allergies because their damaged intestine allows for the absorption of whole proteins.
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Food Allergy Labeling
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49. Meeting Protein Needs: Nitrogen Balance
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50. General Protein Requirements
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51. Varying Protein Needs of Athletes
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52. Protein and Amino Acid Supplements
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53. Choosing Protein Wisely
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54. Types of Vegetarian Diets
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55. Nutrient Needs with a Vegan Diet
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56. Copyright 2010, John Wiley & Sons, Inc.
Soy Protein
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57. What Should I Eat? Protein Sources
Get protein without too much saturated fat
Plan on poultry or fish.
Choose lean cuts of red meat.
Grill, roast, or broil so that the fat will end up in the pan or the fire.
Choose low-fat or reduced-fat milk.
Eat both animal and plant proteins
Have your beef or chicken in a stir-fry with lots of vegetables.
Serve a small portion of meat over noodles.
Add nuts and seeds to snacks and salads.
Have a meatless meal at least once a week.
Go with beans
Try hummus—made from ground chickpeas and sesame seeds.
Add kidney beans or chickpeas to soups.
Snack on soy beans.
Enjoy tacos or burritos stuffed with pinto beans or black beans.
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End of Chapter 6
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