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NU FS 305 > Chapter 6 - Protein > Flashcards

Chapter 6 - Protein Flashcards

1
Q

How many different amino acids are used to make proteins?

A

20

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2
Q

Define

Protein

A

Large complex molecules composed of amino acids

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3
Q

What element is protein the primary source of in our diets?

A

Nitrogen

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4
Q

How many essential amino acids are there?

A

9; histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

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5
Q

What is the structure of an amino acid?

A
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6
Q

What reaction occurs to link amino acids together?

A

Condensation reaction (removal of water)

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7
Q

What does the sequence of amino acids in each protein determine?

A

Its unique shape and function

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8
Q

What does it mean if an amino acid is conditionally essential?

A

Nonessential amino acids that become essential in certain circumstances, such as illness or pregnancy

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9
Q

Acronym for essential amino acids: These Ten Valuable Amino Acids Have Long Preserved Life In Man

A
  • Tryptophan
  • Threonine
  • Valine
  • Arginine (conditional)
  • Histidine
  • Lysine
  • Phenylalanine
  • Leucine
  • Isoleucine
  • Methionine
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10
Q

How many amino acids are in a dipeptide? Tripeptide? Polypeptide?

A

2, 3, >50

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11
Q

What is the primary structure?

A
  • sequence of amino acids joined together
  • weak attraction within chain: H+ on one amino acid attracts O- on nearby amino acids
  • Determines the type of protein and the way it folds
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12
Q

What is the secondary structure?

A
  • weak attraction within chain: H+ on one amino acid attracts O-on nearby amino acids
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13
Q

What is the tertiary structure?

A
  • hydrophilic and hydrophobic side chains
  • disulphide bridges
  • Twists and folds in chain, which are joined together by the disulphide bridges
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14
Q

What happens to the structure and function of a protein if it gets damaged?

A

Regardless of what level the protein is damaged, it may result in a non-functional proten

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15
Q

What is a sequencing errors?

A

Changes in protein structure and function; sickle cell anemia is an example as it has one different aa from a regular hemoglobin

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16
Q

What happens when a protein is dentaured and when does it occur?

A
  • Denaturation is the loss of structure (unfolding); its a reduction in solubility and functionality
  • It occurs >60 degrees, and at acidic pH
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17
Q

What happens to protein in the mouth?

A

Chewing and crushing moisten protein-rich foods and mix them with saliva to be swallowed

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18
Q

What happens to protein in the stomach?

A

Hydrochloric acid (HCl) uncoils protein strands and activates stomach enzymes (protein turns into smaller polypeptides)

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19
Q

What does HCl do in the stomach?

A
  • Denatures protein structure
  • Activates pepsinogen to pepsin
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20
Q

What happens to proteins in the small intestine and with the pancreas?

A

Pancreatic and small intestinal enzymes split polypeptides further:
* polypeptides into tri, dipeptides and aas
Then enzymes on the surface of the SI cells hydrolyze the peptides and absorb them:
* Peptides into amino acids

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21
Q

What does Pepsin do in the stomach?

A
  • Cleaves proteins to smaller polypeptides and some free amino acids
  • Inhibits pepsinogen synthesis
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22
Q

Why is pepsin released as pepsinogen?

A

prevents the auto-digestion of protective proteins in the lining of the digestive tract

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23
Q

Define

Pepsin

A

A gastric enzyme that hydrolyzes protein. Pepsin is secreted in an inactive form, pepsinogen, which is activated by hydrochloric acid in the stomach.

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24
Q

What does enteropeptidase do?

A

In the SI, it converts pancreatic trypsinogen to trypsin

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25
Q

What does trypsin do in the SI?

A
  • Inhibits trypsinogen synthesis
  • Cleaves peptide bonds next to the amino acids lysine and arginine
  • Converts pancreatic procarboxypeptidases to carboxypeptidases
  • Converts pancreatic chymotrypsinogen to chymotrypsin
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26
Q

What does chymotrypsin do in the SI?

A
  • Cleaves peptide bonds next to
    the amino acids phenylalanine, tyrosine, tryptophan, methionine, asparagine, and histidine
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27
Q

What does carboxypeptidases do in the SI?

A
  • Cleave amino acids from the acid
    (carboxyl) ends of polypeptides
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28
Q

What does Elastase and Collagenase do in the SI?

A
  • Cleave polypeptides into smaller polypeptides and tripeptides
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29
Q

What does Intestinal tripeptidases do in the SI?

A
  • Cleave tripeptides to dipeptides and amino acids
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30
Q

What does Intestinal dipeptidases do in the SI?

A
  • Cleave dipeptides to amino acids
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31
Q

What does Intestinal aminopeptidases do in the SI?

A

Cleave amino acids from the amino ends of small polypeptides (oligopeptides)

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32
Q

How are the three ways proteins gets absorbed?

A
  1. Brush Border Membrane Na+ dependent transporters
  2. BBM Na+- independent transporters
  3. Basolateral Membrane
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33
Q

How do BBM Na+ dependent transporters work?

A
  • Works with a sodium electrochemical gradient
  • Bind Na+ which causes confirmational change, bind aa, and then sodium and aa get transported into the intestinal cell
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34
Q

How does protein absorption within intestinal cells?

A
  • Cytoplasmic peptidases hydrolyze di, tripeptides to amino acids
  • It is absorbed where it enters the hepatic portal vein
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35
Q

What happens to intact proteins in protein absorption?

A
  • generally not absorbed due to BBM peptidases
  • no transporters on BL membrane for proteins
  • proteins can not permeate between intestinal cells
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36
Q

Where does protein go in postprandial metabolism?

ex. 30g meal

A
  • 10g to synthesis and turnover
  • 4g to intestine
  • 4g to the muscle/kidney/adipose
  • 12g to the liver where its turned into urea
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37
Q

Acronym for Protein Functions

A
  • Structure
  • Hormone
  • Immunity
  • Transport
  • Sensation
  • Movement
  • Enzymes
38
Q

What is the function of enzymes?

A
  • Needed for chemical reactions
  • Brings substances together (synthesis) or break them down (catabolic)
39
Q

What is the function of hormones?

A
  • Messengers in the body; they can target cells to alter metabolism, and regulate function

ex. insulin, glucagon, GIP

40
Q

How do proteins function as transporters?

A
  • Important in the transport of nutrients in the body (ex. lipoproteins)
  • Proteins in cell membranes transport substances in and out of the cell
41
Q

How do proteins function in fluid and electrolyte balance?

A
  • Proteins attract water
  • The correct balance between intracellular and extracellular proteins is needed to create fluid balance
42
Q

How does edema occur?

A

This occurs when extracellular plasma proteins are low. This results in protein moving into the interstitial space of tissues, which draws water into it, into the tissue in particular, and causes it to swell

43
Q

How do proteins act as buffers?

A
  • They can accept and release hydrogen ions to maintain pH in body fluids within a narrow range
44
Q

What occurs to proteins and the body if there is extreme pHs?

A

The proteins can be denatured and cause acidosis/alkalosis

45
Q

How do proteins function as antibodies?

A
  • antibodies are produced by B-cells in response to antigens, xenobiotics, allergens
  • Required to protect against disease, provides immunity
  • Protein is important in immune function (Maintaining all epithelial barriers) (immune cell synthesis and function)
46
Q

Where are epithelial barriers found?

A

Skin, GIT, Respiratory, Reproductive

47
Q

When is protein used for energy?

A

When there is an inadequate supply of dietary carbohydrates

48
Q

How is protein used as an energy supply? (I.e. there is insufficient carbs)

A
  • Glucogenesis used the carbons from aas to make glucose
  • Nitrogen is then excreted in urine
49
Q

Where are amino acids stripped to become glucose?

A

Either the pyruvate or TCA cycle

50
Q

Define

Amino Acid Pool

A

Amino acids derived from the diet or protein degradation

51
Q

What does protein synthesis and degradation determine in metabolism?

A

Determines the nitrogen balance, which is a marker of protein synthesis or breakdown

52
Q

What is a limiting amino acid?

A

If just one amino acid that is needed to make a protein is not available, the protein will not be synthesized. That aa which is not available is considered limiing

53
Q

What are common examples of limiting amino acids?

A

Lysine, Methionine, Threonine, Tryptophan

54
Q

What five things regulate muscle protein synthesis?

A
  1. Insulin
  2. Testosterone
  3. Growth Hormones
  4. Some AAs
  5. Contraction and stretch
55
Q

What three things regulate muscle protein degradation?

A
  1. Glucagon
  2. Epinephrine
  3. Mediators of inflammation
56
Q

Define

Protein Turnover

A

Synthesis of new protein to replace degraded protein

57
Q

Protein turnover accounts for what percentage of resting energy expenditure?

A

10-25%

58
Q

What does nitrogen balance or maintenance mean?

A

Nitrogen intake (synthesis) = Nitrogen loss (degradation)

59
Q

When does positive nitrogen balance occur?

A

During growth, pregnancy, and/or replenishment

60
Q

When does negative balance occur?

A

During Starvation/Malnutrition, Injury, Illness

61
Q

How do amino acids turn into urea in the liver?

A

Ammonia is produced from deaminated aas; this combines with CO2 to make Urea

62
Q

If amino acids are not oxidized immediately for energy, what can they be used for?

A
  • Gluconeogenesis
  • Fatty acid synthesis (ketogenic aas turn into Acetyl CoA for the FA synthesis)
63
Q

How much of our body protein turns over each day?

A

0.2-0.4%

64
Q

What are protein requirements based upon?

A

Ensuring there is enough protein to replace losses, sustain turnover, and help growth

65
Q

What is the RDA for protein?

A

0.8g/kg of body weight

66
Q

What is the protein recommendation for athletes?

A

1.2-1.7g/kg

67
Q

How much should protein contribute to total energy intake?

A

10-35%

68
Q

What is a complete/high-quality protein?

A

A protein source which has all essential amino acids in sufficient amounts; animal sources are complete

69
Q

What is the digestibility of differing protein sources?

A
  • Animal sources: 90-99%
  • Plant sources 70-90% (soy/legumes 90%)
70
Q

What does the Protein Digestibility-Corrected Amino Acid Scores (PDCAAS) mean?

A

Between 0 and 1; 1 is for the sources that are most digestible and most balanced for essential aa content

71
Q

What effect does protein have on heart disease?

A

Diets that are high in animal protein associated with elevated cholesterol; homocysteine levels in blood increase risk of CVD
This is why its recommeneded that meat intake is limited

72
Q

What effect does protein have on cancer?

A
  • High red meat or processed meat consumption is positively associated with risk of colon cancer
  • Cooking meat at high temperature or over open flame can create carcinogens such as heterocyclic amines
73
Q

What effect does protein have on osteoporosis?

A

Calcium excretion increased with high protein intake
* need a high Ca:ptn ratio to balance and protect bones from Ca depletion

74
Q

What effect does protein have on kidney disease?

A

Protein does not cause kidney disease but people with chronic kidney disease have to monitor protein intake

75
Q

Define

Plant-Based Diet

A

A diet of mostly plant foods with limited intake of animal products is associated with reduced risk of chronic disease

76
Q

Define

Complementary Foods

A

protein sources (foods) that together supply all 9 essential amino acids.

77
Q

Define

Protein-energy undernutrition (PEU)

A

A disorder caused by inadequate intake of protein, energy, and nutrients

78
Q

Who is predominantly affected by PEU?

A

Children; 4:1 ratio

79
Q

What are the two common forms of severe PEU?

A

Marasmus and Kwashiorkor

80
Q

What is Marasmus?

A

Severe inadequate intake of protein, energy, and other nutrients
* Caused by starvation or malabsorption

81
Q

What are the symptoms of marasmus?

A
  • Severe wasting of muscle and adipose tissue
  • Stunted physical growth and brain development
  • Anemia
  • Fluid and electrolyte imbalances
82
Q

What is Kwashiorkor?

A

recent or acute extremely low protein intake and food deprivation following weaning, complicated by infections

83
Q

What is the symptoms of kwashiorkor?

A
  • Some weight loss and muscle wasting
  • Edema and fatty liver
  • Retarded growth and development
  • Skin sores and brittle hair
84
Q

What is the difference between marasmus and kwashiorkor?

A

Kwashiorkor is acute, while marasmus is chronic. Kwashiorkor also has edema and fatty liver, and a higher risk of mortality. Overall, marasmus is an adaptation while Kwasiorkor is a complication

85
Q

What prevents adaptation to PEU in Kwashiorkor?

A

The response to the infection uses energy and protein which prevents the lowering of energy expenditure and protein turnover.

86
Q

Globally, what are the most common deficiencies?

A

Protein-energy, iron, Vitamin A, and iodine

87
Q

What nutrients are predominantly involved in immune function?

A
  • Protein
  • Vitamin A
  • Vitamin C
  • Zinc
88
Q

What is PEM?

A

Protein energy malnutrition

89
Q

Who at risk of PEM in Canada?

A
  • Those in poverty, homeless, isolated rural areas
  • Elderly
  • People with EDs; drug and alcohol addictions
  • People living with muscle wasting conditions
90
Q

How should the adequate amount of protein be determined?

A

By looking at gram requirements vs. calorie % requirements; 50g = 10% of energy but you may need 100+ g

NU FS 305 (13 decks)

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