Chapter 5: Proteins Flashcards

1
Q

Importance of protein

A

critical to growth and development
role can be overstated if it is elevated above other nutrients
protein functions optimally only when energy intake from CHO and fat is sufficient

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2
Q

Amino acid (AA)

A

basic component of proteins
contain carbon, hydrogen, oxygen, and nitrogen
20 AA’s are used by the body to make various proteins - 9 are indispensable (essential/body can’t make them); 11 are dispensable (non-essential/can be made by liver or found in food) with 6 being conditionally indispensable (during periods of stress/starvation body can’t make enough)

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3
Q

Issue of protein deficiency

A

in western countries where few healthy adults are at risk for amino acid deficiencies
those at risk for low protein intake include those with eating disorders, the frail elderly, those with food insecurity, and people with liver or kidney disease

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4
Q

Protein quality

A

based on the amounts and types of amino acids and the extent to which the amino acids are absorbed
measure by the digestible indispensable amino acid score

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5
Q

Complete proteins

A

animal sources
contain all the indispensable amino acids in the proper amounts and proportions to each other to prevent amino acid deficiencies and to support growth

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6
Q

Incomplete proteins

A

plant sources
lack one or more of the indispensable amino acids or the proper concentrations
doesn’t have all the essential amino acids

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7
Q

Complementary proteins

A

combining two incomplete proteins
when consumed during the same day they can be nutritionally equal to a complete (animal) protein

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8
Q

Peptide

A

two or more amino acids that are combined
dipeptide = two amino acids
tripeptide = three amino acids
polypeptide = four or more amino acids
most proteins are polypeptides and are made up of many amino acids

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9
Q

Functions of protein in the body

A

1) Enzymes - necessary to catalyze (speed up) reactions; unique structure of each enzyme interacts with its substance; specific to molecule that it must interact with
2) Hormones and other regulators - hormones are compounds that act as chemical messengers to regular metabolic reactions; AA’s regulate critical metabolic pathways
3) Structural proteins - proteins of muscle and connective tissue; proteins found in skin, hair, and nails
4) Transport proteins - like delivery trucks of the body
5) Immune system proteins - immune system is protein-based; deficient in protein = decrease immune response

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10
Q

Digestion

A

begins in the stomach
protein is denatured by gastric juices containing HCl which allows other enzymes to break them down further
HCl activates pepsin which is an enzyme that will breakdown the proteins into smaller unites
generally breaks down very large polypeptides into smaller units that are still quite large

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11
Q

Absorption

A

takes place in the small intestine
2/3 of amino acids are absorbed in the form of dipeptides or tripeptides, and the other 1/3 are absorbed as individual amino acids
different protein carriers have affinity with certain amino acids
indispensable amino acids are absorbed more rapidly than dispensable amino acids
once absorbed, he body does not distinguish between the amino acids originally obtained from exogenous or endogenous sources
once absorbed, the majority of amino acids will remain in the liver for metabolism with a small amount circulating in the blood and being transported to other parts of the body
amino acids that are not absorbed are excreted in feces
some amino acids will not leave the small intestine cells because they will be used to make cellular proteins with those not used being released into the blood via the portal vein

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12
Q

Transportation and Storage

A

after absorption, some amino acids are transported to the liver whereas others circulate in the blood
liver monitors the supply of amino acids and dictates which amino acids will be transported to which tissues (with the exception of BCAA’s due to low amounts of BCAA transferase in liver)
50-65% of amino acids found in liver with the remaining being in amino acid pool
10-25% of resting metabolism is expended each day to synthesize and degrade proteins

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13
Q

Amino acid pool

A

free amino acids that are circulating in the blood or in the fluid found within or between cells
always in flux as a result of food intake, exercise, and the breaking down or building of tissues, especially skeletal muscle
constant flux known as protein turnover
consist of amino acids that are absorbed from food but do not remain in the liver
amino acids in this pool are involved in anabolic and catabolic processes

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14
Q

Livers role in metabolism of protein and AA’s

A

major site for amino acid metabolism by monitoring the body’s AA needs and responds accordingly with anabolic or catabolic processes

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15
Q

Anabolic

A

building complex molecules from simple ones

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16
Q

Catabolic

A

breakdown of complex molecules into simple ones

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17
Q

Deamination

A

comes from first removal of amino group from the amino acids
part of catabolism

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18
Q

Transamination

A

comes second
transfer of the amino group to another carbon skeleton
part of both catabolism and anabolism

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19
Q

Amino acid pool

A

anabolic process = synthesis of skeletal muscle protein that uses amino acids from the pool to synthesize the new proteins
catabolic process = when skeletal muscle proteins are degraded and amino acids are returned to the amino acid pool

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20
Q

Anabolic functions (occurs in the liver)

A

liver enzymes (amino acids are incorporated), plasma proteins (where the remaining amino acids go), synthesis of muscle protein, albumin (protein that circulates in the blood and is made in the liver), manufacturing of compounds (ie. creatine)
many of the proteins made in the liver are synthesized and released in response to infection or injury

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21
Q

Catabolic functions

A

amino acids are not stored for future use like CHO and fats, but the so-called storage site protein is skeletal muscle
in extreme circumstances, protein can be removed from skeletal muscle but the removal of a large amount of AA’s has a negative effect on muscle’s ability to function so the body tries to protect skeletal muscle from being used in this way

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22
Q

Amount of energy in protein

A

protein yields about 4 kcal/g
CHO and fats are used first, then proteins last if needed
known as protein sparing effect

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23
Q

Protein metabolism during exercise

A

proteolysis (muscle breakdown) occurs when the body is stressed (ie. endurance exercise) and is stimulated by cortisol
in endurance exercise as muscle glycogen stores decline substantially, the skeletal muscle uses some amino acids for energy
metabolic response is influenced by the CHO content of athlete’s diet (ie. low CHO diet and CHO depleted = oxidation of amino acids is increased and vice versa)
body prefers to use CHO when exercising, amino acids are back up energy source
3-5% of energy comes from amino acids, but during prolonged exercise that amount is higher
amino acids are also used for gluconeogenesis (convert to glucose for energy) - 18 of 20 amino acids can be converted to glucose

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24
Q

Ammonia

A

by-product of the breakdown of amino acids
must be filtered out in the urine
nitrogen is also lost in urine every day

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25
Q

Resistance training

A

results in muscle protein breakdown at time of exercise, but eating protein during rest and recovery is extremely important as it results in a positive protein balance

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26
Q

Breakdown and building of protein

A

body is constantly doing these processes
healthy adults turn over 300g of protein a day
1-2% of total protein in the body is degraded each day (mostly from skeletal muscle)
80% of amino acids are synthesized into new proteins, 20% are broken down
5g of nitrogen (30g of protein) is urinated out

27
Q

Nitrogen balance and Net protein balance

A

nitrogen balance is the difference between nitrogen intake nitrogen loss
exercise temporarily brings body into nitrogen balance
during growth phases want the body to be in a positive nitrogen balance
overtraining and starvation diets can bring the body into a negative nitrogen balance
food and recovery must include protein intake to bring the body back into a nitrogen balance
protein turnover is difference between protein synthesis and protein degradation

28
Q

Labile protein reserves

A

something that is readily or frequently undergoes change
found in the liver and other organs
allows the body to respond to very short-term changes in protein intake
allows the body to protect the skeletal muscle from being used as an amino acid source for short-term emergencies

29
Q

Short and Long-term changes in body protein

A

labile protein reserves and amino acid pool

30
Q

Starvation state

A

rate of protein synthesis is decreased by 30% or greater during starvation
tissue most affect = skeletal muscle
amino acids in skeletal muscle are used to protect the visceral tissues
opposite of what happens under normal circumstances (ie. labile protein reserve)

31
Q

Skeletal muscle protein synthesis

A

many factors influence protein muscle synthesis and degradation - one’s genetic potential for cellular protein synthesis; strongly influenced by exercise, specifically strength training
strength training stimulates both protein synthesis and protein breakdown (mainly synthesis) with the greatest increase in myofibrillar proteins
feeding promotes anabolic state in the muscle, particularly is the meal contains adequate amino acids and is consumed immediately or within 2 hours after exercise
insulin plays roles in anabolic process by stimulating protein synthesis and acting to inhibit protein degradation

32
Q

Exercise effect on the immune system

A

moderate exercise has a positive effect on immune system
athletes at risk for immunodepression = prolonged training session 90-120 minutes or more moderate to high intensity exercise
strenuous bout of exercise = immune system drops for 3-24 hours
athlete susceptibility to infection is multifactorial and more research is needed to isolate the influence of exercise in humans
positive effects = reduction in systemic inflammation (good thing)

33
Q

Recommended protein consumption

A

dietary reference intake (DRI) for adults is 0.8 g/kg/body weight
athletes should plan the type (quality), distribution, and timing of protein intake - 1.2-2.0 g/kg/day general guidelines for athletes
guidelines are under the assumptions that total energy intake is adequate and the quality of protein is good
range for athletes depending on exercise levels (intensity, duration, periodization)
intake depends on goals for skeletal mass, muscle growth, etc.
sufficiency and appropriate timing for protein intake is required
older adults consume at least 1.2 g/kg/day to avoid sarcopenia
when energy intake is deficient, protein intake should be minimum 1.8 g/kg/day to prevent decreased skeletal muscle mass

34
Q

Amino acid metabolism

A

involves the catabolism of amino acids which takes place in the liver
during this process ammonia is produced (toxic to body)
ammonia must be converted urea for excretion
all humans have max rate of urea synthesis, exceptionally high intake of protein could leads to an elevated blood ammonia level (dangerous medical condition)
a suggested maximum intake of protein is 2.5 g/kg/day, but healthy adults appear to be able to tolerate protein intakes as high as 3.5 g/kg/day without adverse side effects

35
Q

High-quality proteins

A

not all proteins are capable of stimulating muscle protein synthesis to the same degree
those that maximize muscle protein synthesis are high-quality proteins or proteins with high biological value - found in food like milk and dairy products, meat, fish, eggs, and soy products; protein supplements can also contain high-quality proteins that are derived from whey, casein, soy, and egg proteins

36
Q

How to maximize muscle protein synthesis?

A

recommended that athletes consume 0.25-0.3 g/kg/day of protein immediately after exercise, if possible, or at least within 2 hours after exercise ends

37
Q

Timing of protein intake

A

catabolic state is followed by anabolic state, an environment that allows for recovery from the acute effects of exercise and for skeletal muscle growth
first hour or two after exercise is referred to as anabolic window
intake of protein after resistance exercise increases the amount of amino acids in the blood which activates signalling molecules necessary to promote muscle protein synthesis

38
Q

Protein consumption after resistance exercise

A

immediately after exercise, when possible, and preferably within 2 hours after exercise consume protein
high-quality protein containing a large amount of indispensable amino acids like egg white, whey, casein, and soy
~15-25g of protein as a food, beverage, or protein supplement
for maximum protein synthesis, high quality protein source containing ~1.7-2.4 g of leucine (ie. milk, dairy products, eggs, or supplements containing whey protein isolate)

39
Q

CHO-protein consumption after exercise

A

CHO consumed immediately after exercise are beneficial to restore muscle glycogen and stimulate the release of insulin which increases amino acid uptake and inhibits muscle degradation
many athletes will consume beverages with both CHO and protein is most beneficial for recovery

40
Q

CHO-protein consumption during exercise

A

during resistance training there are thoughts that consuming CHO and protein can offset muscle protein breakdown and enhance muscle protein synthesis

41
Q

Protein consumption before exercise

A

insufficient evidence to suggest that protein consumption prior to exercise is beneficial for recovery

42
Q

Protein consumption before sleep

A

at least 40g of protein before sleep can help minimize muscle protein breakdown and help muscle protein synthesis especially if athlete has been resistance training
for maximum muscle protein synthesis some athletes may set an alarm midway through their sleep cycle to consume a protein-containing beverage or supplement

43
Q

Athletes and protein consumption

A

majority of athletes consume sufficient protein
no current evidence that high-protein diets result in renal insufficiency
no evidence that high-protein diets adversely affect bone health
large amounts of protein can result in dehydration because additional water is needed to metabolize protein
need to watch CHO, fat and overall caloric intake
those at risk for low protein involve athletes struggling with eating disorders or are restricting energy in order to keep body weight or fat level

44
Q

Energy intake effect on protein intake

A

amount of protein required is related to overall energy intake
adequate energy intake from CHO or fat spares amino acids from being used for energy and helps maintain nitrogen balance
adjustments to protein intake will need to be made when energy intake is deficient
amount of protein needed depends on the magnitude of the energy deficit and whether it is acute or chronic
higher protein diet is recommended to the athlete who is dieting as a way to protect against the loss of muscle mass

45
Q

Long-term, substantial energy deficit

A

typically result in low protein intake
chronic energy deficit = more protein is needed to maintain nitrogen balance
if energy and protein intake are too low theres a reduction in the synthesis of some body proteins, degradation of skeletal muscle proteins, and returns the body to a balanced state but a lower functional level
net protein balance will be achieved but at the expenses of training, recovery, performance and health
starvation conditions leads to changes in hormonal balances because food is not being consumed so little insulin is being produced
muscle and fat cells become resistant to the insulin that is present
without insulin, protein synthesis is further reduced because insulin promotes the uptake of amino acids by muscle cells
hormonal status favours the breakdown of skeletal muscle protein to provide amino acids to make glucose

46
Q

Dieting and lean body mass

A

70-80% of weight lost from adipose tissue
20-30% from lean body mass, almost entirely from skeletal muscle

47
Q

Dieting recommendations for athletes

A

daily energy deficit should be moderate (~500kcal)
resistance exercise must be performed
daily protein intake should be at least 1.8-2.7 g/kg
high quality protein sources should be consumed
post exercise protein consumption = 0.25-0.3 g/kg
leucine containing and whey protein sources
meals or substantial snack should be distributed evenly throughout the day
need adequate CHO for recovery

48
Q

“Making weight”

A

involves short term energy deficits
for competing in a certain weight category
substantially reduce caloric intake for a short time, goal to lose body weight through fat and water loss
raises serious concerns about hydration status, the potential for heat illness, maintenance of skeletal muscle mass, ability to exercise due to depleted glycogen stores, hypoglycemia, and declines in RMR
some sports have enacted regulations based on minimum weight formula to determine the appropriate weight category for each competitor

49
Q

Low protein intake and immune system

A

immune system highly dependent on protein
low protein intake usually accompanies low energy intake and low nutrient intake
some immune mechanisms are impaired

50
Q

Impact of injury/infection on protein status

A

injury or infection has effect on protein status
increased loss of nitrogen from the body and negative nitrogen balance which is intensified if a fever is present
illness typically results in lack of appetite which creates negative nitrogen balance and leads to body depending on its stores and reserves for amino acids treatment should include restoring protein status
bacterial infections takes 2-3 times the duration of the infection to restore the protein that has been lost
protein intake of an additional 0.2-0.3 g/kg/day during recovery period

51
Q

Protein sources

A

found in both animal and plant foods
animal source includes meat, fish, poultry, eggs, milk, and milk products
plant sources include beans, legumes, nuts, and seeds
grains and vegetables contain smaller amounts than other protein-containing foods but are often consumed in large quantities and contribute a reasonable amount to total daily protein intake

52
Q

Vegetarian and vegan diet

A

vegetarians may consume animal products like eggs
vegans do not consume any product derived from animals
well-planned vegetarian diets are appropriate for all individuals
emphasize protein rich vegetarian foods
soy protein isolate is considered comparable in quality to animal protein
can support optimal performance if the diet contains the proper quantity and quality of protein and is sufficient in calories

53
Q

Protein supplements

A

neither more or less effective than food proteins for skeletal muscle growth
may be more convenient due to portability, preparation, and easy storage

54
Q

Protein supplement ingredients

A

contain whey, casein, egg, and soy proteins
whey and casein come from milk
whey protein concentrate and whey powder contain lactose
whey protein isolate is concentrated source of protein because both the CHO and the fat are removed
casein high in glutamine

55
Q

Whey

A

fast-acting protein
high percentage of indispensable amino acids

56
Q

Casein

A

slow-acting protein
lower amount of indispensable amino acids

57
Q

AA’s supplements

A

appear to be safe at recommended doses
many fall short when it comes to effectiveness
complicated physiological processes cannot be affected to a large degree by a single factor

58
Q

Beta-alanine

A

effective for buffering muscle pH in athletes performing high-intensity exercise lasting 1-40 minutes

59
Q

HMB

A

not effective in resistance trained athletes
small to very small increases in strength in untrained individuals
emerging evidence suggests that skeletal muscle breakdown may be reduced with high intensity or prolonged endurance exercise

60
Q

BCAAs

A

not effective for improving performance
little evidence for reduction of postexercise fatigue
some promise for immune system support

61
Q

Glucosamine/Chondroitin sulfate

A

generally not effective for reducing joint pain or increasing functionality in those with osteoarthritis

62
Q

Glutamine

A

unlikely to be effective

63
Q

Growth Hormone releasers (arginine)

A

effective for stimulating growth hormone release
not effective for increasing muscle mass or strength

64
Q

Nitric oxide (NO)/arginine alpha-ketoglutarate (AAKG)

A

may be effective at increasing performance in untrained individuals, conflicting results with athletes