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171 terms

Nutrition Ch. 6

STUDY
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________ is found in proteins but not in carbohydrates and fats.
nitrogen
What makes proteins unique in comparison to the composition of carbs and fats?
nitrogen
What is the primary factor that differentiates one amino acid from another?
the side group
______ is found in certain amino acids.
Sulfur
What are terms used to classify amino acids in the diet?
Essential, nonessential and conditionally essential
How many different kinds of amino acids make up proteins?
20
What are contained in an amino acid?
An acid group, an amino group and a central carbon atom
How many different amino acids are used in the synthesis of proteins?
20
What is the simplest amino acid?
glycine
Proline is not an ___________ in human nutrition.
essential amino acid
What can the body not use for the synthesis of a nonessential amino acid?
an essential mineral
What is classified as conditionally essential when dietary intake of phenylalanine is insufficient or the body cannot normally metabolize phenylalanine.
tyrosine
What type of amino acid has to be supplied by the diet?
Essential amino acid
What is required to bind two molecules of glycine together and to release a molecule of water?
Condensation
What is the resulting structure when two amino acids ore bound together chemically?
Dipeptide
what is the composition of a tripeptide?
three amino acids bound together.
What is the amino acid sequence of a protein referred to?
the order of amino acids in a peptide chain
what type of amino acid can be synthesized by the body?
dispensable amino acid
In comparison to the well-defined structure of starch, what is the most important factor that allows for the synthesis of thousands of different proteins?
the number of different amino acids
20 amino acids would be classified as what?
a polypeptide
what do you get when you bind glycine, lysine and valine?
tripeptide
what accounts for the secondary structures in proteins?
the weak electrical attractions
how many polypeptide chains is hemoglobin made up of?
4 polypeptide chains
what is an example of a protein with a quaternary polypeptide structure?
hemoglobin
What is the process by which heat or acidity disrupts the normal shape of a protein chain?
denaturation
The application of heat or acid to a protein that causes its shape to change is known as what?
denaturation
what is the process that results in hardening of an egg when exposed to heat?
denaturation
After a hamburger is eaten, in what organ is the hydrolysis of its proteins initiated?
Stomach
In what organ is pepsin active?
stomach
What digestive enzyme would be most affected in people who are unable to produce hydrochloric acid?
pepsin
Protein-hydrolyzing enzymes are commonly known as what?
proteases
what is the function of a protease?
hydrolyze proteins
What is the name of the inactive form of the protein-splitting enzyme in the stomach?
pepsinogen
what is the chief function of pepsin?
cleaves proteins into smaller polypeptides
what percentage of dietary protein is hydrolyzed in the mouth?
0%
what is pepsinogen also known as?
zymogen
what products are absorbed into the circulation after digestion of proteins?
free amino acids, and a few dipeptides and tripeptides
what is the usual fate of orally ingested enzyme supplements?
Digested by gastrointestinal proteases
What is an oligopeptide?
A string of about 4-9 amino acids
what are some characteristics of enzymes?
they are all catalysts, they have a protein structure and they can be destroyed by heat.
the structure of pepsin is also the structure of what?
proteins
what are some of the fates of amino acids in the intestinal tract?
some may be used for energy by the intestinal cells, some may be used for synthesis of proteins by the intestinal cells, and they may be transported across the intestinal cell membrane to the capillaries.
what source of amino acids would be best absorbed in normal, healthy people?
whole proteins
Approximately how many different proteins are present in the human body?
30,000
The code to make a protein is carried by a strand of messenger RNA is a process of what?
protein synthesis
Messenger RNA is constructed from a DNA template to carry instructions is a characteristic of what?
protein synthesis
The process whereby messenger RNA is made from a DNA template is called what?
transcription
What is a ribosome?
A structure upon which proteins are assembled
what are some features of protein in nutrition?
the study of the body's proteins in known as proteomics, protein synthesis requires messenger RNA and transfer RNA, and the synthesis of a protein by following the genetic code is known as gene expression.
What type of anemia is from having abnormally-shaped hemoglobin.
sickle-cell anemia
A common genetic variation which causes a change in the amino acid sequence in the structure of hemoglobin leads to what disease?
sickle-cell anemia
what is a characteristic of sickle-cell anemia?
the abnormal structure of the hemoglobin alters the shape of the red blood cell.
What is the structure of an enzyme?
Protein
What protein is intimately involved in the formation of scar tissue in wound healing?
Collagen
What type of protein would the body make in order to heal a wound?
Collagen
Which of the following is a characteristic of hormones?
Act as messenger molecules
Collagen does not function as what type of protein?
transport protein
What is the relationship between body proteins and water?
Proteins attract water
what are some associations between protein nutrition and the body's water balance?
inadequate protein intake may lead to edema, insufficient protein synthesis by the liver may lead to edema, and excessive protein intake burdens the kidneys to excrete unused nitrogen.
what do the conditions known as acidosis and alkalosis refer to?
the disruption of the body's pH balance
Tissue swelling that results from water accumulating between cells is known as what?
edema
Proteins, because they attract hydrogen ions, can act as what?
buffers
What function does a buffer perform?
Helps maintain a constant pH
What is regulated primarily by the buffering action of proteins?
pH balance
How do sodium and potassium travel into and out of cells?
There are transport proteins within the cell membrane that pick up and release the minerals across the membrane
What is opsin?
A light-sensitive protein
what protein inactivates foreign bacteria and viruses?
antibodies
The body's usual response to detection of antigens is to synthesize what?
antibodies
Which of the following describes the structure of an antibody?
huge protein molecule
Which of the following is involved in the clotting of blood?
fibrin
How many grams of nitrogen are contained in a 2500-kcalorie diet that provides 15% of the energy as protein?
15
Which of the following may be used to determine protein utilization?
nitrogen balance
When nitrogen taken into the body exceeds nitrogen losses, we say the person is in what?
positive nitrogen balance.
The sum of protein synthesis and degradation defines what?
protein turnover
What is the amino acid pool?
A mix of essential and nonessential amino acids derived from protein breakdown and dietary protein intake
What describes the state of nitrogen balance for a normal, healthy 35-year-old person who weighs 60 kg and consumes a diet that provides 75 g of protein and adequate energy?
equilibrium
what does the body's amino acid pool consists of?
both essential and nonessential amino acids.
What is the nitrogen balance of a person who consumed a 3500-kcalorie diet containing 10% protein and excreted a total of 12 grams of nitrogen?
+2 g
what would describe the state of nitrogen balance of a person who ingested 16 g of food nitrogen and lost 19 g of nitrogen?
negative balance
What is the usual state of nitrogen balance for healthy infants, children, and pregnant women?
positive balance
What amino acid is used to synthesize the neurotransmitter serotonin and the vitamin niacin?
Tryptophan
What is meant by protein turnover?
The synthesis and degradation of body proteins
What is the fate of excess dietary protein?
After absorption, the extra amino acids will be rapidly degraded
When amino acids are deaminated, the immediate products are ammonia and often a ______.
keto acid
Protein sparing in the body is best achieved when a person ingests ______.
adequate levels of carbs and fat
A person who is starving is losing _____.
glycogen, protein, and fat.
Removal of the amino group from an amino acid is an illustrations of what?
a deamination reaction
what is the most likely side effect of a high-protein, low-carbohydrate diet?
increased thirst
what are some compounds that contain nitrogen?
urea, enzymes and ammonia
what is a consequence of excess protein intake?
Increased production and excretion of urea
what precursors of urea synthesis?
increased production and excretion of urea
What is the process whereby an amino group is combined with a keto acid to form an amino acid?
Transamination
In the metabolism of amino acids for energy, what is the fate of the amino group?
Excreted as urea
The body's need for water increases on a diet high in _____.
protein
The body's need for water increases on a diet high in
Liver dysfunction
What is the most likely reason for having an abnormally high blood urea level?
Kidney dysfunction
A prominent result of transamination reactions is the synthesis of ____.
nonessential amino acids.
a man who has a high blood ammonia concentration, most likely has a poorly functioning _________.
liver
a woman who has a high blood urea content, most likely has a poorly functioning ________.
kidney
A reference protein equals or exceeds the essential amino acid requirements of what population groups?
preschool aged children, adolescents, and the elderly.
What is the percent digestibility of most plant proteins?
70-90
What is the percent digestibility of most animal proteins?
90-99
Which of the following food proteins has the best assortment of essential amino acids for the human body?
egg
what is related to the quality of a food protein?
essential amino acid balance
What primary factor governs the quality of a food protein?
Essential amino acid content
In the study of protein nutrition, what term describes the amount of amino acids absorbed from a given amount of protein consumed?
Digestibility
what is not considered to be a source of high-quality protein in human nutrition?
corn
what animal-derived proteins is classified as a poor-quality protein?
gelatin
What is a "limiting" amino acid in a protein?
An essential amino acid present in insufficient quantity for body protein synthesis to take place
If the diet is lacking an essential amino acid, what will be the course of action?
Protein synthesis will be limited
what is not be a limiting amino acid in the diet?
glycine
what is characteristic of protein nutrition in vegetarians?
Most vegetarians eating a variety of foods need not balance essential amino acid intake at each meal
What is the Daily Value for protein based on a 2000-kcalorie intake?
50g
What is complementary protein nutrition?
A strategy that combines plant proteins in the same day to improve the balance of essential amino acids
In general, the protein quality in grains would be most improved by the addition of a plant protein rich in what?
lysine
In general, the protein quality of legumes would be most improved by the addition of a plant protein rich in what?
methionine
Relative to animal proteins, what amino acid is present in lesser amounts in proteins of legumes?
tryptophan
Approximately what percentage of children worldwide have protein-energy malnutrition?
25%
Acute protein-energy malnutrition in children is characterized by _____.
low weight for height
Chronic protein-energy malnutrition in children is characterized by ______.
short height for age,
what are some are characteristics of protein-energy malnutrition?
it is found in hospitalized adults, it is found in elderly living alone, and it is common in people with anorexia nervosa.
Marasmus occurs most commonly in children of what ages?
6-18 months
what would you expect to see in a person with kwashiorkor?
Edema, Dysentery, and Increased infection rate
what is associated with the presence of tissue edema in kwashiorkor?
Low concentration of blood protein
what are some characteristics of marasmus?
Results in a low resistance to disease, Occurs most commonly in children aged 6 to 18 months, and Results in little or no fat under the skin to insulate against cold.
what is a feature of malnutrition?
Dysentery is common and leads to diarrhea and nutrient depletion.
how does the rapid onset of protein-energy malnutrition occurs in kwashiorkor?
It is typically seen in patients who are 1-3 years old due to the sudden change in diet arising from their being weaned from breast milk after the birth of a sibling
What term describes the illness a child develops when the next child is born?
Kwashiorkor
what is a condition is associated with edema?
Diminished concentration of blood proteins and hormones, which causes fluid to leak from the blood vessels
Kwashiorkor typically develops in children of what ages?
18-24 months
In kwashiorkor, what is the loss of hair color is indirectly related to?
inadequate intake of tyrosine
In kwashiorkor, what mineral is often present in an unbound form that promotes bacterial growth?
Iron
What is the most likely explanation for the fatty liver that develops from protein deficiency?
Inability of the liver to synthesize lipoproteins for fat export
what is a feature of kwashiorkor?
It is typically precipitated in the undernourished child who has an infection`
What is the usual initial therapy for the treatment of kwashiorkor?
Fluid balance restoration
Excessive amounts of homocysteine in the blood are thought to increase the risk for ______.
heart disease
Supplements of what amino acid is reported to lower blood pressure and reduce homocysteine levels?
Arginine
what are known to raise the levels of homocysteine?
alcohol intake, cigarette smoking and coffee consumption.
What type of diet is advised to rehabilitate a severely malnourished child?
low protein
what is a feature of homocysteine?
it is increased in the blood of coffee drinkers
what is a description of a relationship between protein/amino acids and heart disease?
Elevated blood homocysteine levels are associated with smoking cigarettes and drinking alcohol
What ratio (mg:g) of calcium to protein intake is believed to promote optimal bone health?
20:1
what is a description of an association between protein intake and kidney function?
restricting protein intake may slow the progression of kidney disease
In relation to the range of protein intake as a percentage of energy intake, what would be the highest safe level of protein intake for a 60-kg adult ingesting 2500 kcalories?
219g
what is a description of a relationship between protein intake and calcium metabolism?
Calcium excretion rises with increasing intake of animal-derived proteins
What is the RDA for protein for a 48-kg woman?
38 g
What is the ratio of calcium to protein intake (mg to g) for most U.S. women?
9:1
What would be the primary principle of wise diet planning as related to protein nutrition?
Moderation
what is a feature of the protein RDA?
The recommendations are generous`
If protein needs are expressed per kilogram of body weight, which of the following describes the requirements of infants?
Greater than adults
What is the range of daily protein intake, in g/kg, recommended for athletes?
1.2-1.7
Your friend Jill has just joined her community college soccer team. How much protein should she consume each day?
1.2-1.7 g/kg
what is an assumption made in the formulation of the RDA for protein?
Dietary carbohydrate and fat intakes are adequate
what are some assumptions made by the committee in setting the RDA for protein?
adequate kcalories will be consumed, protein eaten will be of mixed quality, and other nutrients in the diet will be adequate.
what is a feature of protein nutrition?
The protein RDA assumes that dietary protein is from a mix of low- and high-quality sources
What is the percentage of total energy derived from protein in a diet containing 50 grams of protein and 2000 kcalories?
10
If a person consumes 65 grams of protein and a total of 2700 kcalories per day, approximately what percentage of energy would be derived from protein?
10
approximately how many grams of protein are found in one quart of milk?
32
what is a feature of whey protein?
it is a waste product of cheese production
Jim, a college baseball player, tells you that he has started to take glutamine supplements. How would you advise him?
Since single amino acids do not occur naturally in foods, they offer no benefit to the body and may even be harmful
what is a feature of the branched-chain amino acids?
they may be helpful in treatment of advanced liver failure
What amino acid has been linked to the development of the rare blood disorder eosinophilia myalgia in people who took it as a supplement?
tryptophan
What amino acid supplement has been advertised in the popular media for treating herpes infections?
lysine
The disease phenylketonuria is related chiefly to abnormal metabolism of what?
a certain amino acid
what is the study of how food interacts with genes is known as?
nutritional genomics
what is the study of how environmental factors influence the expression of genes without altering the DNA is known as?
epigenetics
Approximately what percentage of a person's genes are similar to that of an unrelated person?
99.9
What dispensable amino acid becomes essential in people with PKU?
tyrosine
what is the incidence of PKU in infants in the United States?
1 in every 15,000 births
what are some characteristics of phenylketonuria?
it is a single-gene disorder, it leads to a dietary requirement for tyrosine, and it results in mental retardation unless treatment is started in infancy.
Dietary restriction of phenylalanine combined with adequate tyrosine is the usual treatment for people born with what disorder?
PKU