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KIN 428 > Protein Metabolism > Flashcards

Protein Metabolism Flashcards

1
Q

What is the AMDR for protein for adults (19+)?

A

percentage of total calories from protein: 10-35%

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2
Q

What is the AMDR for protein for 1-3yrs?
What is the AMDR for protein for 4-18yrs?

A

5-20% (1-3yrs)

10-30% (4-18yrs)

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3
Q

What happens to required percentage of total calories from protein as we increase in age?

A

increases as we age

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4
Q

What are the 9 functions of proteins?

A
  1. structural
  2. transport
  3. enzyme
  4. hormone/neurotransmitter
  5. immune
  6. acid-base balance
  7. fluid balance
  8. energy (4kcal/g)
  9. movement
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5
Q

How much energy in one gram of protein?

A

4kcal/gram

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6
Q

Compared to carbohydrates, what differentiates protein in how it is processed?

A

presence of nitrogen in protein

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7
Q

Digestion of protein enables amino acids to enter what areas?

A

blood, liver, and peripheral tissues (i.e., muscle)

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8
Q

Upon digestion, proteins are degraded to amino acids by what? Where does this occur?

A

proteases - in the stomach and small intestine

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9
Q

How long does it take before amino acids are cleared once they enter the blood?

A

5-10min

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10
Q

What does the rate of digestion of proteins depend on?

A

protein type and composition of the meal/snack (ex, also high fat? will cause digestion to take longer)

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11
Q

Describe how protein is digested.

A

proteins broken down to polypeptides in the stomach

polypeptides broken down to tripeptides, dipeptides, and amino acids

final breakdown of AA in small intestine

AA absorbed into portal vein and transported to liver

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12
Q

What is the difference between fast absorption proteins and slow absorption proteins? Give examples.

A

Fast absorption - induces a large increase in whole-body protein synthesis and oxidation, minimal effect on whole body protein breakdown
Ex. whey protein, soy protein

Slow absorption - induces a change in whole body protein turnover, small increase in synthesis and oxidation, large reduction in protein breakdown
Ex. casein

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13
Q

How many amino acids are necessary for protein synthesis?

A

all 20

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14
Q

What are the 9 essential amino acids (EAAs)?

A

histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
HILKMFTWV

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15
Q

What are the 3 branched chain amino acids (BCAAs)?

A

Leucine, isoleucine, valine

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16
Q

Complete dietary proteins includes what?

A

Includes all 9 EAAs

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17
Q

What are the 6 conditionally indispensable amino acids?

A

arginine, cysteine, glutamine, glycine, proline, tyrosine
RCGQPY

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18
Q

What is a complete vs. non-complete protein?

A

complete - usually animal products (contains all 9 EAAs)

vegetarian sources - often incomplete and have to be combined to ensure all proteins are being met

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19
Q

Do plant sources of protein reach the same muscle protein synthetic response?
Therefore what must occur with a vegetarian diet?

A

lower in plant sources than animal based protein because plants lack leucine content and have a lower digestibility

with vegetarian diet - portions may need to be larger with plant-based products

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20
Q

What is the standard that we want to be met for protein content in dairy products?

A

Want at least 8g protein/cup from things

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21
Q

What is nitrogen balance?

A

ability of the body to retain nitrogen (protein balance)

dietary input (grams of N2/day) = amount excreted

ex. what young healthy adults should reach on an adequate diet

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22
Q

What is a negative nitrogen balance?
What can cause this?

A

amount excreted (g N2/day) > dietary input

Can be caused by disease state, trauma, over-training (individual is losing muscle protein)

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23
Q

What is positive nitrogen balance?

A

retaining protein to support growth and development

dietary input (g N2/day) > amount excreted

ex. adults on a calorie sufficient diet

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24
Q

Nitrogen balance can usually be maintained when consuming what amount of protein in sedentary individuals? (current RDA for protein)

A

0.8g/kg BW/day

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25
Q

What is nitrogen balance dependent on?

A

adequate protein intake and total energy intake (kcal/day)

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26
Q

A diet that is deficient in energy (kcal), despite adequate protein will result in what?

A

a negative nitrogen balance

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27
Q

What is the most important metabolic fate of amino acids?

A

formation of body tissues, hormones, enzymes, antibodies, nucleotides, etc.

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28
Q

Do humans store excess amino acids?

A

no we cannot, due to the inability to store excess nitrogen

29
Q

How long does protein digestion take?

A

can take several hours

30
Q

since humans do not store amino acids, what process occurs?

A

process of deamination

31
Q

What is deamination?

A

the nitrogen (amino group) on the amino acid is removed, leaving a carbon molecule (alpha-ketoacid) for oxidation

excess nitrogen must be excreted, so the liver forms ammonia (NH3) from excess nitrogen

32
Q

What symptom can occur due to increasing levels of ammonia?

A

fatigue!

33
Q

What are the steps of protein digestion? What happens to excess protein/nitrogen that must be excreted?

A

nitrogen group travels to the liver and gets converted to NH3, then gets converted to urea, then enters the kidneys to be excreted in the urine

34
Q

What is the difference between glucogenic amino acids and ketogenic amino acids?

A

glucogenic: AAs that can be used to form glucose via gluconeogenesis

ketogenic: AAs that are metabolized to acetyl-coA can then enter the krebs cycle or be converted to fat
ex. leucine, lysine

35
Q

How can the liver use nitrogen-containing amino groups from excess amino acids?

A

Can combine them with alpha-ketoacids (from fat or CHO metabolism)

36
Q

Amino acids can form other nitrogen containing compounds such as:

A

creatine, nucleotides

37
Q

When would an athlete need to use protein as a FUEL source?

A

once out of the carb source, goes into gluconeogenesis (forming energy from non-carb sources)

38
Q

How might an athlete find themselves in a low CHO availability situation?

A

may not take enough in
output so great that they used up all their storage and expended all their carbs (now relying on other energy systems)

39
Q

When too much lean tissue are used to fuel the body, what may occur?

A

loss of strength/endurance, compromised immune/endocrine/musculoskeletal function

40
Q

If an exercising individual wants to maintain muscle mass, is it just essential to have adequate protein for muscle growth?

A

no, also require sufficient CHO, fat and total calories

41
Q

Why are calories from CHO and fat so important?

A

they create a protein sparing effect

42
Q

What might a low CHO diet do to protein? How does exercise influence protein?

A

Low CHO diet - may cause muscle protein to be oxidized for energy

exercise may increase protein losses (urine, sweat, GI)

when you take away carbs, becomes more reliant on that AA pool for energy

43
Q

Protein contributes to what % of energy during exercise?

A

~5%

44
Q

What happens to protein catabolism as intensity/duration increases? When?

A

as intensity/duration increases, protein catabolism increases
increased protein catabolism when muscle glycogen is depleted

45
Q

Is the rate of energy production from protein fast or slow compared to CHO or FAT?

A

protein - slow

46
Q

As exercise duration increases and CHO stores decrease, proteins contribute ______ to energy expenditure.

A

contribute more

47
Q

How will an increase in exogenous CHO intake affect enzyme for protein breakdown?

A

inhibition of these enzymes

48
Q

Is the current RDA of 0.8g/kg BW/day enough when the goal is optimal sport performance?

A

definitely not

49
Q

Dietary protein intake necessary to support metablic adaptations, repair, remodeling, and for protein turnover generally ranges from __-___?

A

1.2-2.0g/kg BW/day

50
Q

New guidelines for protein intake should be based on what factors?

A

1) A periodized training and nutrition program
2) Timing between training sessions
3) Optimal training adaptation to specific training sessions
4) Athlete training status (highly trained may require less vs. new training stimulus)
5) Athlete’s training goals
6) Body composition goals
7) Food choices nutrient needs
8) Daily energy considerations

51
Q

Would a new training regimen require more or less protein?

A

more; as you are more trained, may require less

52
Q

What improvement may be caused by protein intake pre or during for post-exercise muscle protein synthesis?

A

post-exercise muscle protein synthesis rates can be elevated more rapidly, due to increased AA availability to muscle

53
Q

How might protein intake during exercise help?

A

it may delay onset of fatigue (improved time to exhaustion trial but not consistent for TT performance)

54
Q

What dosage of protein is ideal for maximal muscle protein synthesis for strength/resistance training?
What happens above this dosage?

A

20-25g protein every 3hrs

above dosage: increased AA oxidation (no advantage above that)

55
Q

Protein intake during resistance training?

A

providing the body with AAs during exercise may increase muscle protein synthesis and suppress breakdown

56
Q

For recovery nutrition, what are 4 goals post-workout?

A

1) rehydration (replace fluids and electrolytes)
2) restoration of muscle glycogen (CHO)
3) restoration/repair to damaged protein/muscle tissue
4) start the remodelling process (create an anabolic environment)

57
Q

How much high quality protein should be consumed after training? (g/kg BW)

A

15-25g
0.25-0.3g/kg BW

58
Q

Why don’t we have % daily value for protein on food labels?

A

no & because it’s so variable
better to look at absolute amount for individual

59
Q

Is the exact timing of the anabolic window post workout well-defined?

A

no, but when primary goal is to increase lean muscle mass –> consume as soon as possible after training
(especially over a longer duration >11/2hrs, new exercises, new training loads, or if next training session is within 8hrs

60
Q

Muscle protein synthesis is optimized in response to exercise when ~__g essential amino acids are consumed early in recovery.

A

~10g EAA

61
Q

best protein type in recovery?

A

dairy sources of protein seem to be superior to other tested (dietary) proteins, largely due to leucine content and the digestion and absorption kinetics of BCAA in fluid based dairy foods.

62
Q

What diet change involving protein may help when cutting calories, cutting bodyweight, or decreasing fat mass?

A

increase protein
decrease fat and carbs

decreased CHO intake (approx. 40%kcal) + increased protein intake has been shown to increase fat loss and preserve lean tissue

63
Q

Why would high protein diet help with weight loss?

A

creates a greater feeling of satiety

thermic effect of food (TEF) or energy cost of eating is higher in protein
(highest 1 hr post meal)

64
Q

How does RMR for protein differ from CHO and fat?

A

20-30% RMR for protein
5-10% RMR for CHO
<0-5% RMR for fat

65
Q

What are some potential risks in a high protein intake/diet?

A

supplementing? supplement purity/content

increased fat and cholesterol intake if from animal products

maybe increased workload on kidneys and liver

greater excretion of calcium

lack of variety - micronutrient deficiencies

dehydration

66
Q

Who may need careful monitoring to ensure they are getting the protein and energy they require?

A

Young athletes growing and performing

Athletes restricting intake

Athletes trying to “make weight”

Restriction due to allergies

People with health issues

Vegetarian athletes

67
Q

Is protein supplementation necessary for athletes?

A

athletes likely get enough protein in diet, therefore, protein supplementation not necessary

68
Q

What should the timing and amount of protein be? Does this differ depending on the person?

A

every 3-4 hours - 20-25g
based on 86kg male (less for lighter individuals and females)

KIN 428 (12 decks)

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