Chapter 6

Question 1

Compounds of carbon, hydrogen, oxygen, and nitrogen and arranged as strands of amino acids (some amino acids contain the element sulfur). One key difference from carbohydrates and fats is that this contain nitrogen atoms in addition to the carbon, hydrogen, and oxygen atoms that all three energy-yielding nutrients contain.

Answer 1

Protein

Question 2

Building blocks of protein. The nitrogen atoms of proteins give the name amino (which means “nitrogen containing”).

Answer 2

Amino acids

Question 3

A strand of amino acids that makes up a protein my contain how many different kinds of amino acids?

Answer 3

20

Question 4

The nitrogen-containing portion of an amino acid. All amino acids have the same simple chemical backbone consisting of a single carbon atom with both this (the nitrogen containing part) and an acid group attached to it.

Answer 4

amine group

Question 5

Each amino acid also has this distinctive chemical chain attached to the center carbon of the backbone. This chain gives each amino acid its identity and chemical nature. Some 20 amino acids, each with a different chain, make up most of the proteins of living tissue. This chain make the amino acids differ in size, shape, and electrical charge.

Answer 5

side chain

Question 6

Learn:
While amino acids form large protein molecules, the side chains help determine the protein’s molecular shape and behavior.

Question 7

A body cannot make nine of the amino acids or makes them too slowly to meet its needs. This is where these amino acids come into play. Without these, the body cannot build the proteins it needs to do its work. Can be replenished only from foods, a person must frequently eat the foods that provide them.

Answer 7

essential amino acids ( 9 are essential amino acids)

Question 8

An amino acid that is normally nonessential but must be supplied by the diet in special circumstances when the need for it exceeds the body’s ability to produce it.
Example: Under special circumstances, a nonessential amino acid can become essential. For example, the body normally makes tyrosine (a nonessential amino acid) from the essential amino acid phenylalanine. If the diet fails to supply enough phenylalanine or if the body cannot perform the conversion for some reason, then tyrosine becomes this.

Answer 8

conditionally essential amino acid

Question 9

Recycling Amino Acids:

Answer 9

The body not only makes some amino acids but also breaks protein molecules apart and reuses their amino acids. Both food proteins after digestion and body proteins when they have finished their cellular work are dismantled to liberate their component amino acids. Amino acids from both sources provide the cells with raw materials from which they can build the protein molecules they need. Cells can also use the amino acids for energy and discard the nitrogen atoms as wastes. By reusing intact amino acids to build proteins, the body recycles and conserves nitrogen, a valuable commodity, while easing its nitrogen disposal burden.

This recycling system also provides access to an emergency fund of amino acids in times of fuel, glucose, or protein deprivation. At such times, tissues can break down their own proteins, sacrificing working molecules before the ends of their normal lifetimes, to supply amino acids and energy to the body’s cells.

Question 10

How Amino Acids Build Proteins:

Answer 10

In the first step of making a protein, each amino acid is hooked to the next.
A chemical bond, called a peptide bond, is formed between the amine group end of one amino acid and the acid group end of the next.
The side chains bristle out from the backbone of the structure, giving the protein molecule its unique character.
- Amino acids do not remain straight and each one are chemically attracted to each other causing some segments of the strand to coil, somewhat like a metal spring and then form a globular structure.
Other strands link together in other ways to form different structures that perform specific functions.

Question 11

Chemical bond. A bond that connects one amino acid with another, forming a link in a protein chain. Is a complete strand of amino acids. Is formed between the amine group end of one amino acid and the acid group end of the next.

Answer 11

Peptide bond

Question 11

A string of about 10-50 amino acids bonded together

Answer 11

polypeptide

Question 12

A particular protein that performs the tasks of carrying and storing materials in their interiors. Are water-soluble and some form hollow balls.

Answer 12

globular shape

Question 13

A form of this protein acts like glue between cells. The chief protein of most connective tissues, including scars, ligaments, and tendons, and the underlying matrix on which bones and teeth are built.

Answer 13

collagen

Question 14

The most fascinating proteins are these which act on other substances to change them chemically. In other words, proteins that facilitate chemical reactions without being changed in the process. Protein catalysts.

Answer 14

enzymes

Question 15

The large, globular protein molecule that is packed into the red blood cells by the billions and carries oxygen around the body via the bloodstream- is made of four associated protein strands, each holding the mineral iron.

Answer 15

hemoglobin

Question 16

For each protein, there exists a standard amino acid sequence, and that sequence is specified by the genes. Often, if a wrong amino acid is inserted, the result can be disastrous to health causing a disease such as this. in which hemoglobin, the oxygen-carrying protein of the red blood cells, is abnormal—is an example of an inherited variation in the amino acid sequence. Normal hemoglobin contains two kinds of protein strands. In sickle-cell disease, one of the strands is an exact copy of that in normal hemoglobin, but in the other strand, the sixth amino acid is valine rather than glutamic acid. This replacement of one amino acid so alters the protein that it is unable to carry and release oxygen. The red blood cells collapse from the normal disk shape into crescent shapes. If too many crescent-shaped cells appear in the blood, the result is abnormal blood clotting, strokes, bouts of severe pain, susceptibility to infection, and early death. Thanks to rapid advances in genetic research, gene-based therapies to treat sickle-cell disease may become a reality.

Answer 16

Sickle-cell disease

Question 17

Protein Synthesis:

Answer 17

1.) The DNA serves as a template to make strands of messenger RNA (mRNA). Each mRNA strands copies exactly in the instructions for making some protein the cells needs.
2.) The mRNA leaves the nucleus through the nucleus membrane. DNA remains inside the nucleus.
3.) The mRNA attaches itself to one of the protein-making machines of the cell, a ribosome.
4.) transfer RNA 9tRNA), collects amino acids from the cell fluid. Each tRNA carries its amino acid to the mRNA, which dictates the sequence in which the amino acids will be attached to form the protein strands. Thus the mRNA ensures the amino acids are lined up in the correct sequence.
5.) As the amino acids are lined up in the right sequence, and the ribosome moves along the mRNA, an enzyme attaches one amino acid after another to the growing protein strand. The tRNA are freed to return for more amino acids. When all the amino acids have been attached, the completed protein is released.
6.) Finally, the mRNA and ribosome separate. It takes many words to describe these events, but in the cell, 40-100 amino acids can be added to a growing protein strand in only a second. Furthermore, several ribosomes can simultaneously wok on the same mRNA to make many copies of the protein.

Question 18

Nutrients, including amino acids and proteins, do not change DNA structure, but they greatly influence gene expression. This is the science of how food components, such as nutrients, interact with the body’s genetic material. As research in this advances, researchers hope to one day use nutrients to influence a person’s genes in ways that reduce that individual’s disease risks, but for now, that day is remote. The Think Fitness feature addresses a related concern of exercisers and athletes about whether extra dietary protein or amino acids can trigger the synthesis of muscle tissue and augment strength.

Answer 18

nutritional genomics

Question 19

Can Eating Extra Protein Make Muscles Grow Stronger?

Answer 19

No and Yes
No: Athletes and fitness seekers cannot stimulate their muscles to gain size and strength simply by consuming more protein or amino acids. Physical work is necessary to trigger the genes to build more of the muscle tissue needed for sport. ]
Yes: Reflects research suggesting that well-timed protein intakes can stimulate muscle protein synthesis. Protein intake cannot replace exercise in this regard, however, as many supplement sellers would have people believe.
Exercise generates cellular messages that stimulate the DNA to begin synthesizing the muscle proteins needed to perform the work. Current evidence does not support the claim that protein supplementation can increase muscle strength or athletic performance in well-fed people, regardless of its timing.

Question 20

When a protein molecule loses its shape, it can no longer function as it was designed to do. This is how many agents damage living cells: they cause this of their proteins. It is the irreversible change in a protein’s folded shape brought about by heat, acids, bases, alcohol, salts of heavy metals, or other agents. In digestion, however, this is useful: it unfolds and inactivates the proteins in food, exposes their peptide bonds to the digestive enzymes that sever them. Also this occurs during the cooking of foods. Cooking eggs denatures their proteins and makes them firm. Heat unfolds and uncoils protein structures, causing eggs to become firm as they cook. Among egg proteins that heat denatures, two are notable in nutrition. One binds the vitamin biotin and the mineral iron: when this protein is denatured, it releases biotin and iron, making them available to the body. The other slows protein digestion; denaturing this protein allows digestion to proceed normally. Many well-known poisons are salts of heavy metals such as mercury and silver; these poisons denature protein strands wherever they touch them. The common first-aid antidote for swallowing a heavy-metal poison is to drink milk. The poison then acts on the protein of the milk rather than on the protein tissues of the mouth, esophagus, and stomach. Later, vomiting can be induced to expel the poison that has combined with the milk.

Answer 20

Denaturation

Question 21

For digestion, proteins must be broken down into amino acids. But nothing happens to proteins until they reach what organ first?

Answer 21

Stomach

Question 22

Protein Digestion:

Answer 22

1.) Strong hydrochloric acid produced by the stomach denatures proteins in food. This acid helps uncoil the protein’s tangled strands so that molecules of the stomach’s protein-digesting enzyme can attack the peptide bonds. You might expect that the stomach enzyme, being a protein itself, would be denatured by the stomach’s acid. Unlike most enzymes, though, the stomach enzyme functions best in an acid environment. Its job is to break other protein strands into smaller pieces. The stomach lining, which is also made partly of protein, is protected against attack by acid and enzymes by the coat of mucus secreted by its cells.

Proteins (enzymes), activated by acid, digest proteins from food, denatured by acid. Digestion and absorption of other nutrients, such as iron, also rely on the stomach’s ability to produce strong acid. The acid in the stomach is so strong (pH 1.5) that no food is acidic enough to make it stronger; for comparison, the pH of vinegar is about 3.

By the time most proteins slip from the stomach into the small intestine, they are denatured and cleaved into smaller pieces. A few single amino acids have been released, but most of the original protein enters as long strands—polypeptides. In the small intestine, alkaline juice from the pancreas neutralizes the acid delivered by the stomach. The pH rises to about 7 (neutral), enabling the next enzyme team to accomplish the final breakdown of the strands. Protein-digesting enzymes from the pancreas and intestine continue working until almost all pieces of protein are broken into single amino acids or into strands of two or three amino acids, dipeptides or tripeptides summarizes the whole process of protein digestion.

Question 23

What Happens to Amino Acids After Protein is Digested?

Answer 23

The cells all along the small intestine absorb single amino acids. As for dipeptides and tripeptides, enzymes on the cells’ surfaces split most of them into single amino acids, and the cells absorb them, too. Dipeptides and tripeptides are also absorbed as-is into the cells, where they are split into amino acids and join with the others to be released into the bloodstream. A few larger peptide molecules can escape the digestive process altogether and enter the bloodstream intact. Scientists believe these larger particles may act as hormones to regulate body functions and provide the body with information about the external environment. The larger molecules may also stimulate an immune response and thus play a role in food allergy.
The cells of the small intestine possess separate sites for absorbing different types of amino acids. Chemically similar amino acids compete for the same absorption sites. Consequently, when a person ingests a large dose of any single amino acid, that amino acid may limit absorption of others of its general type. The Consumer’s Guide () cautions against taking single amino acids as supplements partly for this reason.

Once amino acids are circulating in the bloodstream, they are carried to the liver, where they may be used or released into the blood to be taken up by other cells of the body. The cells can then link the amino acids together to build proteins that they keep for their own use or liberate them into lymph or blood for other uses. When necessary, the body’s cells can also use amino acids for energy.
Shorter terms:
The cells of the small intestine complete digestion, absorb amino acids and some larger peptides, and release them into the bloodstream for use by the body’s cells.

Question 24

The body needs what to grow new cells and to replace old or damaged ones?

Answer 24

dietary amino acids

Question 25

Protein is important in helping replace worn-out cells and internal cell structures. Each of the following cells lives for only these set amounts of days:

Answer 25

Red blood cells: 3-4 months and must be replaced by a new cell produced by the bone marrow
Cells of intestinal lining: constantly being replaced every 3 days
Skin cells: die and rub off often and new ones grow from underneath, like most cells –> cells –> constantly build and break down proteins while replacing their own internal working proteins

Question 26

When cells reform because others are dying off and breaking down it is called this. Known as the entire process of breakdown, recover, and synthesis. Or the continuous breakdown and synthesis of body proteins involving the recycling of amino acids.

Answer 26

protein turnover

Question 27

Roles of Body Proteins:

Answer 27

• gene expression
• Acid Base Balance
  -Blood Clotting
• Maintain fluid and electrolyte balance
• structure and movement: most body’s protein exists in muscle tissue. Allow the body to move. These proteins release amino acids when energy is low, as in starvation. Other protein is seen everywhere including tendons, cartilage, blood vessels, skin, teeth, scars, nails, hair, etc.
• Includes the works of Enzymes, Hormones, Antibodies
• Proteins specialize in transporting substances such as lipids, vitamins, minerals and oxygen, around the body. Examples: the protein hemoglobin within the red blood cells, which carries oxygen from the lungs to the tissues, and the lipoproteins, which transport lipids in the watery blood.

Question 28

Metabolic workhouses. Acts as a catalyst (speeds up a chemical reaction that would happen anyway, but much more slowly). Thousands reside inside a single cell, and each one facilitates a specific chemical reaction.

Answer 28

enzymes

Question 29

Messenger molecules and many are made from amino acids. Various body glands release these when changes occur in the internal environment; this then elicit tissue responses necessary to restore normal conditions.

Answer 29

hormones

Question 30

Which amino acid forms parts of the neurotransmitters epinephrine and norepinephrine, which relay messages throughout the nervous system? Also, the body uses this o make the brown pigment melanin, which gives a brown color to skin, hair, and eyes. In addition, this is converted into the thyroid hormone thyroxine.

Answer 30

tyrosine

Question 31

Peptide hormone of the thyroid gland that regulates to body’s rate of energy use or (metabolism).

Answer 31

thyroxine

Question 32

Another amino acid, tryptophan, serves as starting material for this neurotransmitter and the vitamin niacin.

Answer 32

serotonin

Question 33

Proteins form the immune system molecules that fight diseases.

Answer 33

Antibodies

Question 34

Proteins help maintain the acid–base balance of various body fluids by acting as buffers.

Blood pH is one of the most rigidly controlled conditions in the body. If blood pH changes too much, acidosis (excess acid in blood, below normal pH) or the opposite basic condition, alkalosis (excess base in the blood, above normal pH), can cause coma or death. These conditions constitute medical emergencies because of their effects on proteins. When the proteins’ buffering capacity is filled—that is, when they have taken on all the acid hydrogens they can accommodate—additional acid pulls them out of shape, denaturing them and disrupting many body processes.

Answer 34

Acid base balance

Question 35

Proteins provide the netting on which blood clots are built.

Answer 35

blood clotting

Question 36

Proteins help to maintain the water and mineral composition of various body fluids.

Answer 36

Fluid and electrolyte balance

Question 37

Converting Amino Acids to Glucose:

Answer 37

When amino acids are degraded for energy or converted into glucose, their nitrogen-containing amine groups are stripped off and used elsewhere or are incorporated by the liver into urea and sent to the kidneys for excretion in the urine. The fragments that remain are composed of carbon, hydrogen, and oxygen, as are carbohydrate and fat, and can be used to build glucose or fatty acids or can be metabolized like them.

Question 38

Drawing Amino Acids from Tissues:

Answer 38

Glucose is stored as glycogen and fat as triglycerides, but no specialized storage compound exists for protein. Body protein is present only as the active working molecular and structural components of body tissues. When protein-sparing energy from carbohydrate and fat is lacking and the need becomes urgent, as in starvation, prolonged fasting, or severe calorie restriction, the body must dismantle some of its tissue proteins to obtain amino acids for building the most essential proteins and for energy. Each protein is taken in its own time: first, small proteins from the blood, then proteins from the muscles. The body guards the structural proteins of the heart and other organs until forced, by dire need, to relinquish them. Thus, energy deficiency (starvation) always incurs wasting of lean body tissue as well as loss of fat.

Question 39

Using Excess Amino Acids:

Answer 39

When amino acids are oversupplied, the body cannot store them. It has no choice but to remove and excrete their amine groups and then use the residues in one of three ways: to meet immediate energy needs, to make glucose for storage as glycogen, or to make fat for energy storage. The body readily converts amino acids to glucose. The body also possesses enzymes to convert amino acids into fatty acids. An indirect contribution of amino acids to fat stores also exists—the body speeds up its use of excess amino acids for fuel, burning them instead of fat, making fat more abundantly available for storage in the fat tissue.

The similarities and differences of the three energy-yielding nutrients should now be clear. Carbohydrate offers energy; fat offers concentrated energy; and protein can offer energy plus nitrogen

Question 40

To review the body’s handling of amino acids, let us follow the fate of an amino acid that was originally part of a protein-containing food. When the amino acid arrives in a cell, it can be used in one of several ways, depending on the cell’s needs at the time:

Answer 40

The amino acid can be used as-is to build part of a growing protein.

The amino acid can be altered somewhat to make another needed compound, such as the vitamin niacin.

The cell can dismantle the amino acid to use its amine group to build a different amino acid. The remainder can be used for fuel or, if fuel is abundant, converted to glucose or fat.

When a cell is starved for energy and has no glucose or fatty acids, it strips the amino acid of its amine group (the nitrogen part) and uses the remainder of its structure for energy. The amine group is excreted from the cell and then from the body in the urine. In a cell that has a surplus of energy and amino acids, the cell takes the amino acid apart, excretes the amine group, and uses the rest to meet immediate energy needs or converts it to glucose or fat for storage.

Question 41

When not used to build protein or make other nitrogen-containing compounds, amino acids are “wasted” in a sense. This wasting occurs under any of four conditions:

Answer 41

When the body lacks energy from other sources.

When the diet supplies more protein than the body needs.

When the body has too much of any single amino acid—for example, from a supplement.

When the diet supplies protein of low quality, with too few essential amino acids, as described in the next section.

To prevent the wasting of dietary protein and permit the synthesis of needed body protein, the dietary protein must be of adequate quality: it must supply all essential amino acids in the proper amounts. It must also be accompanied by enough energy-yielding carbohydrate and fat to permit the dietary protein to be used as such.

Question 42

Is needed to build muscle protein, so many athletes take protein powders in hopes of building bigger muscles. It’s true that protein eaten soon after lifting weights or other exertion increases protein synthesis for a while (Chapter 10 describes this effect), but this detail of metabolism does not appear to improve muscle strength or athletic ability. Protein supplements are not “muscles in a bottle,” as they are often advertised—physical work is required to build muscle or prevent its loss.

Answer 42

Dietary Protein

Question 43

Learn:
Protein in a meal contributes to satiety, but “protein drinks” and shakes often add many calories to a day’s intake from good-tasting fats and sugars. In addition, any excess nitrogen, including nitrogen from a protein supplement, must be metabolized and excreted. This places a burden on the kidneys, particularly if they are weakened by disease.

Question 44

Bone broth is a long-simmered gelatin-rich soup, also sold in powdered form, and marketed with comforting images of home. Gelatin arises when collagen, a protein present in bones, dissolves into the broth during long, moist cooking (despite claims, broth contains no actual collagen).

As people age, the protein collagen diminishes in skin, causing sags and wrinkles, and in joints, causing painful movement. Bone broth advocates claim that drinking gelatin in bone broth can restore both youthful-looking skin and pain-free joints, but consuming collagen or gelatin cannot do these things. Nor can it make hair glossy or reduce “cellulite.” As a protein source, gelatin is low in quality—it lacks certain essential amino acids necessary for protein synthesis (a later section comes back to protein quality).

Many people try to treat soft, dry, weak, easily breakable fingernails with collagen or gelatin supplements but this doesn’t work, either. Made largely of protein, nails depend on sulfur bonds between amino acids for flexible strength, fatty acids for water resistance, and sufficient water for proper hydration. In addition, the living tissues that form nails need many minerals and vitamins to put these materials into place. Nails, hair, and skin all depend on a nutritious diet to look their best, not protein supplements.

Answer 44

Bone Broth and Collagen

Question 45

Athletes and others often take supplements of these in hopes of building muscle or losing fat. Decades ago, this was found to stimulate muscle protein synthesis when given through a vein to exercised rats, but only for a short time. In people, this supplementation does not appear to enhance muscle protein synthesis, and may in fact suppress it by disturbing the balance of amino acids required to build new muscle proteins. Adequate amounts of ordinary foods containing high-quality protein deliver the right amino acids in the right balance to best support muscle protein synthesis. Regarding safety, excess amounts of this may alter metabolic systems, particularly concerning insulin action. Theoretically, such disturbances could present health risks for people who take the supplements, but research is needed to clarify these associations.

Tryptophan supplements are often sold with promises of relief from insomnia or depression. Tryptophan may be effective for inducing drowsiness, but research is lacking to say with any certainty whether tryptophan supplements can relieve depression. Large daily doses can have side effects, such as temporary nausea or skin problems. People taking antidepressant drugs should consult with their physicians before taking tryptophan supplements.

Answer 45

Branched-chain amino acids (BCAA)

Question 46

In cases of disease or malnutrition, a registered clinical dietitian may employ a special protein or amino acid supplement. Not every patient is a candidate for such therapy, though, because the supplements may stimulate inflammation, which can worsen the condition, or draw water into the digestive tract, which causes diarrhea. Protein supplements can also worsen kidney disease or interfere with the actions of certain medications, allowing diseases to advance unchecked.

A lack of research prevents the DRI committee from setting Tolerable Upper Intake Levels for amino acids. Therefore, no level of amino acid supplementation can be assumed safe.

Growth or altered metabolism makes these people especially likely to be harmed by self-prescribed amino acid supplements:

Answer 46

All women of childbearing age, especially those who are pregnant or lactating

Infants, children, and adolescents

Elderly people

People with inborn errors of metabolism that affect their bodies’ handling of amino acids

Smokers

People on low-protein diets

People with chronic or acute mental or physical illnesses

Question 47

This along with infection may greatly increase the need for protein while making it hard to eat even normal amounts of food. With this, secretion of digestive enzymes slows as the tract’s lining degenerates, impairing protein digestion and absorption. When infection is present, extra protein is needed for enhanced immune functions.

Answer 47

malnutrition

Question 48

Underlying the protein recommendation are these studies. The amount of nitrogen consumed compared with the amount excreted in a given time period. In healthy adults, nitrogen-in (consumed) must equal nitrogen-out (excreted). Scientists measure the body’s daily nitrogen losses in urine, feces, sweat, and skin under controlled conditions and then estimate the amount of protein needed to replace these losses. Under normal circumstances, healthy adults are in nitrogen equilibrium, or zero balance; that is, they have the same amount of total protein in their bodies at all times. When nitrogen-in exceeds nitrogen-out, people are said to be in positive nitrogen balance; somewhere in their bodies more proteins are being built than are being broken down and lost. When nitrogen-in is less than nitrogen-out, people are said to be in negative nitrogen balance; they are losing protein.

Answer 48

nitrogen balance

Question 49

Growing children add new blood, bone, and muscle cells to their bodies every day, so children have more protein, and therefore more nitrogen, in their bodies at the end of each day than they had at the beginning. A growing child is therefore in thiis nitrogen balance. Similarly, when a woman is pregnant, she must be in this nitrogen balance until after the birth, when she once again reaches equilibrium.

Answer 49

Positive Nitrogen Balance

Question 50

This nitrogen balance occurs when muscle or other protein tissue is broken down and lost: nitrogen excretion increases. Illness or injury triggers the release of powerful messengers that signal the body to break down some of the less vital proteins, such as those of the blood, skin, and muscle. This action floods the blood with amino acids, which are then stripped of their nitrogen and used for energy to fuel the body’s defenses and fight the illness. The result is greater nitrogen excretion and this nitrogen balance. Astronauts, too, experience this nitrogen balance. In the stress of space flight and with no need to support the body’s weight against gravity, the astronauts’ muscles waste and weaken. To minimize the inevitable loss of muscle tissue, the astronauts must do special exercises in space.

Answer 50

Negative Nitrogen Balance

Question 51

Provide enough of all the essential amino acids needed by the body to create its own working proteins, whereas low-quality proteins don’t. In other words, dietary proteins containing all the essential amino acids in relatively the same amounts that human beings require. They may also contain nonessential amino acids. Two factors influence this: it’s amino acid composition and its digestibility

Answer 51

high-quality proteins or protein quality

Question 52

Two factors influence a protein’s quality: its amino acid composition and its digestibility.

To build their required proteins, the cells need the full array of amino acids, including the essential amino acids. If a nonessential amino acid (that is, one the cells can make) is unavailable from food, the cells synthesize it and continue attaching amino acids to the protein strands being manufactured. If the diet fails to provide enough of an essential amino acid (one the cells cannot make), the cells begin to adjust their activities. The cells:

Answer 52

Break down more internal proteins to liberate the needed essential amino acid, and

Limit their synthesis of proteins to conserve the essential amino acid.

Question 53

An essential amino acid that is present in dietary protein in an insufficient amount, thereby limiting the body’s ability to build protein. Even so, the normally fast rate of protein synthesis slows to a crawl as cells make do with the proteins on hand. When the this once again becomes available in abundance, the cells resume their normal protein-related activities. If the shortage becomes chronic, however, the cells begin to break down their protein-making machinery. Consequently, when protein intakes become adequate again, protein synthesis lags behind until the needed machinery can be rebuilt. Meanwhile, the cells function less and less effectively as their proteins become depleted and are only partially replaced.

Thus, a diet that is short in any of the essential amino acids limits protein synthesis. An earlier analogy likened amino acids to letters of the alphabet. To be meaningful, words must contain all the right letters. For example, a print shop that has no letter “N” cannot make personalized stationery for Jana Johnson. No matter how many Js, As, Os, Hs, and Ss are in the printer’s possession, the printer cannot use them to replace the missing Ns. Likewise, in building a protein molecule, no amino acid can fill another’s spot. If a cell that is building a protein cannot find a needed amino acid, synthesis stops, and the partial protein is released.

Partially completed proteins are not held for completion at a later time when the diet may improve. Rather, they are dismantled, and the component amino acids are returned to the circulation to be made available to other cells. If they are not soon inserted into protein, their amine groups are removed and excreted, and the residues are used for other purposes. The need that prompted the call for that particular protein will simply not be met.

Answer 53

Limiting amino acid

Question 54

If a person fails to consume all the essential amino acids in proportion to the body’s needs, the body’s pools of essential amino acids will dwindle until body organs are compromised. Consuming the essential amino acids presents no problem to people who regularly eat protein foods containing ample amounts of all of the essential amino acids, such as meat, fish, poultry, cheese, eggs, milk, and most soybean products.
An equally sound choice is to eat a variety of protein foods from plants so that amino acids that are low in some foods will be supplied by the others.
The combination of such protein-rich foods yields these..proteins containing all the essential amino acids in amounts sufficient to support health.
Example: the amino acids of legumes and grains balance each other to provide all the needed amino acids. The complementary proteins need not be eaten together, so long as the day’s meals supply all of them along with sufficient energy and total protein.
Example: peanut butter on whole-wheat bread

Answer 54

Complementary proteins

Question 55

Just as important as measuring a protein’s quality.

Answer 55

Simple measures of the total protein in foods are not useful by themselves—even animal hair and hooves would receive a top score by those measures alone. They are made of protein, but the protein is not in a form that people can use.

This of protein varies from food to food and bears profoundly on protein quality. The protein of oats, for example, is less digestible than that of eggs. In general, proteins from animal sources, such as chicken, beef, and pork, are most easily digested and absorbed (more than 90 percent). Those from legumes, nuts, grains, and other plant foods vary (from 60 to 90 percent). Cooking with moist heat improves protein digestibility, whereas dry heat methods can impair it.

Question 56

Perspective on Protein Quality:

Answer 56

Concern about the quality of individual food proteins is of only theoretical interest in settings where food is abundant. Healthy adults in these places would find it next to impossible not to meet their protein needs, even if they were to eat no meat, fish, poultry, eggs, or cheese products at all. Even healthy vegetarians need not pay attention to balancing amino acids so long as they follow a dietary pattern that is varied, nutritious, and adequate in energy and other nutrients—not made up of, say, just cookies, crackers, potato chips, and juices. Protein sufficiency follows effortlessly behind a balanced, nutritious diet.

For people in areas where food sources are less reliable, protein quality can make the difference between health and disease, or for children, the difference between normal or stunted growth. Whenever food energy is restricted, malnutrition is widespread, the variety of available foods is severely limited, or a single low-protein food, such as fufu made from cassava root, provides most of the calories, the primary food source of protein must be checked because its quality is crucial.

Question 57

When the diet supplies too little protein or lacks a specific essential amino acid relative to the others (a limiting amino acid), the body slows its synthesis of proteins while increasing its breakdown of body tissue protein to liberate the amino acids it needs to build other proteins of more critical importance. Without its most critical proteins, many of the body’s life-sustaining activities would come to a halt. The consequences include slow growth in children, impaired brain and kidney functions, weakened immune defenses, and impaired nutrient absorption from the digestive tract. These conditions often occur in starvation wherein the diet lacks not only protein, but energy, vitamins, and minerals as well. In an elderly person, too little dietary protein may weaken the bones and increase the risk of fractures. Bone fracture in the aged often requires surgery to repair and may have life-threatening consequences. Every effort should be made to ensure that the diet of an elderly person provides the DRI amount of protein every day.

Answer 57

Protein deficiency

Question 58

When you consume too much of something. This involving protein-rich foods offers no benefits and may pose a health risk for people with compromised kidney function.
Most people suspect that Americans eat far too much protein. In fact, the average protein intake for U.S. men stands at 15.5 percent of total calories, with women consuming slightly less at about 15 percent of calories. These amounts stay remarkably stable across populations and are well within the AMDR of between 10 and 35 percent of calories. Stated another way, the AMDR range for protein intake in a 2,000-calorie diet is 50 to 175 grams; the average U.S. daily intake of protein amounts to about 80 grams.

Answer 58

Overconsumption

Question 59

Protein itself does not contribute to heart disease but what are some food sources that can if overly consumed?

Answer 59

Fatty red meats, processed meats, and fat-containing milk products, adds a burden of saturated fat to the diet and crowds out fruits, vegetables, legumes, nuts, and whole grains. People who habitually take in a great deal of animal protein, and particularly processed meats such as lunchmeats and hot dogs, have greater risks of heart disease, certain cancers, and other chronic diseases than those who take in less.

Question 60

Learn:
Animals fed experimentally on high-protein diets often develop enlarged kidneys or livers. In human beings, a high-protein diet increases the kidneys’ workload, but research is insufficient to say whether this alone can damage healthy kidneys or cause kidney disease. In people with kidney stones or other kidney diseases, a high-protein diet may speed the kidneys’ decline. For people with established kidney problems, a somewhat lower protein intake often improves the symptoms of their disease. The challenge then becomes to provide enough protein to support the body’s health, but not more than the damaged kidneys can handle. Choosing plant-based protein sources rather than animal sources may also help delay kidney decline.

Question 61

A protein that forms in grain foods, is best known for providing a pleasing stretchy texture to yeast breads. It also provides bulk and texture to many other foods made from wheat, triticale, barley, rye, and related grains.
Gluten-free diets have no special power to spur weight loss either, despite noisy claims made by diet sellers. In fact, the opposite is often true: many gluten-sensitive people become overweight when they begin eating more food on a gluten-free diet that relieves their symptoms. Manufactured gluten-free foods are often higher in fats, added sugars, and calories than their regular counterparts, making overconsumption of calories likely

Answer 61

Gluten

Question 62

In people with this, gluten triggers an abnormal immune response that inflames the small intestine and erodes the intestinal villi, severely limiting nutrient absorption. The result is a lifelong battle against extreme weight loss accompanied by deficiencies of vitamins, minerals, essential fatty acids, and, in fact, all nutrients. Symptoms often include chronic diarrhea or constipation, vomiting, bloating, and pain, or a long list of disparate symptoms that may delay an accurate diagnosis: anemia, fatigue, aches and pains, bone loss, depression, anxiety, infertility, mouth sores, or an itchy, blistering skin rash.

A blood test revealing high concentrations of certain antibodies can indicate this disease or the similar problem of gluten allergy. To heal their intestines, people with these conditions must eliminate all gluten-containing foods from their diets and then continue avoiding them for the rest of their lives. This is easier said than done because gluten can hide in foods that contain wheat-based additives, such as modified food starch and preservatives. Even corn and rice, naturally gluten-free foods, can be contaminated with gluten if they are milled in machines that also process wheat. The U.S. Food and Drug Administration (FDA) requires food labels to clearly identify ingredients containing wheat and related grains; foods labeled “gluten-free” are held to strict standards.

Answer 62

celiac disease

Question 63

Patients suffer from digestive symptoms resembling those of celiac disease or a gluten allergy, but test negative for these conditions. Some people with NCGS find relief when they eat a gluten-free diet, although the reasons why are not clear. In other words, a poorly defined collection of digestive symptoms that improves with elimination of gluten from the diet.

Answer 63

non-celiac gluten sensitivity

Question 64

What are 3 of the top sources of protein in the US diet? And what foods is an equivalent?

Answer 64

beef, chicken and eggs
legumes and soybeans are equivalent to protein rich meat

Question 65

Are excellent sources of many B vitamins, iron, and other minerals, making them exceptionally nutritious foods. On average, a cup of these cooked contains about 30 percent of the Daily Values for both protein and iron. These do not offer every nutrient, and they do not make a complete meal by themselves. They contain no vitamin A, vitamin C, or vitamin, and their balance of amino acids can be much improved by using grains or other vegetables along with them.

Answer 65

Legumes

Question 66

Are versatile legumes, and many nutritious products are made from them. Heavy use of this in place of meat, inhibit iron absorption. The effect can be alleviated by using small amounts of meat and/or foods rich in vitamin C in the same meal with soy products. The nutrients of these are also available as bean curd, or tofu, a staple used in many Asian dishes. Thanks to the use of calcium salts when some tofu is made, it can be high in calcium.

Answer 66

soybeans

Question 67

Vegetarians and others sometimes use convenience foods made from this. It is soy or other plant-based protein formulated to look and taste like hamburgers or breakfast sausages. In other words, processed soybean or other plant-based protein used in products formulated to look and taste like meat, fish, or poultry.

Answer 67

textured vegetable protein

Question 67

True or False?
Among both men and women and across many ethnic groups, people eating plant-based diets more often maintain a healthier body weight than people eating meat-centered diets. With less obesity, chronic inflammation, a contributing factor associated with many disease states, is also diminished.

Answer 67

True

Question 68

People who eat plant-based diets often have lower blood LDL cholesterol concentrations and die less often from heart disease than do others. Harmful Inflammation that aggravates heart and artery disease is reduced in people eating these diets. Heart disease and early mortality correlate significantly with diets high in processed meat and red meat. If the diet also contains about five servings a day of fruits and vegetables, along with sufficient nuts and legumes, as most plant-based diets do, then LDL cholesterol typically falls, and heart benefits accumulate. In contrast, even this diet can overemphasize sugar-sweetened beverages, refined baked goods, French fries, and other treats is associated with an increased risk of heart disease. Can lower risk of some forms of cancer. may help prevent cataracts, diabetes, diverticular disease, gallstones, and osteoporosis. However, these effects may arise more from what is included in this diet —abundant fruit, legumes, vegetables, milk products, and whole grains than from exclusion of meat and dairy foods.

Answer 68

Vegetarian diets

Question 69

Learn:
How much meat is too much:
An average daily intake of 50 grams (a bit less than 2 ounces) of beef, lamb, or pork (but not poultry) raises the risk of coronary heart disease by 9 percent. The same amount of processed meat, raises the risk by 18 percent.

Question 70

Learn:
The cereals highest in protein quality contain legume flours or extracts, often from soy, a rich source of amino acids that rivals the quality of animal protein for use by the body. In contrast, cereals made solely of grains, such as corn, oats, rice, or wheat, are lower in both protein quantity and quality.

Also, have freeze dried “chips” instead of vegetable chips because they have more preserved nutrients

Question 71

The latest burgers sold in fast-food restaurants and grocery stores are formulated with these molecules, a component of hemoglobin that tricks the taste buds into sensing “meat.” This in the burger is synthesized by genetically engineered yeast, not animals, making the burgers vegan-friendly, yet remarkably similar in taste to meat.

Answer 71

heme