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NUTR 3210 > proteins > Flashcards

proteins Flashcards

1
Q

phenylketonuria

A
  • when a person is unable to breakdown Phe into Tyr
  • Tyr becomes an essential AA
  • solution: limit Phe in diet and supplement with Tyr
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2
Q

liver disease (cirrhosis)

A
  • impairs Phe and Met catabolism
  • Tyr and Cys are usually synthesized from Phe and Met
  • Tyr and Cys become essential because they cannot be synthesized
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3
Q

Basic AAs

A
  • Lysine: involved in the production of carnitine, limiting in grains
  • Arginine: conditionally essential (for infants)
  • Histidine: used to produce histamine (inflammation)
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4
Q

Acidic AAs

A
  • Aspartate
  • Glutamate
    both non-essential
    can react with basic amino groups to form Gln and Asn
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5
Q

Asparagine and Glutamine

A
  • both non-essential
  • made when amino group reacts with asp and glu
  • glutamate is used to make GABA
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6
Q

Glycine

A
  • non-essential
  • used to produce porphyrin (component of heme)
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7
Q

what are the essential amino acids

A
  • histidine
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • valine
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8
Q

branched chain AAs

A

leucine, isoleucine and valine
- all are essential
- high levels in circulation (not catabolized in the liver)
- promote protein synthesis
- BCAA levels high in protein suppliments

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9
Q

Methionine

A
  • 1st step in the synthesis of all proteins
  • limitting in legumes
  • makes cystine
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10
Q

hydroxylated (OH) AAs

A

Serine and threonine
- OH in their side chains is important for the phosphorylation PTM of proteins

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11
Q

Cystine

A
  • sulfur containing
  • non-essential
  • made from methionine*
  • used in glutathione synthesis in oxidant defence
  • “spares” methionine when it is consumed in diet
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12
Q

Aromatic AAs (rings)

A
  • phenylalanine: used to make Phe
  • tyrosine: spares “Phe”
  • Tryptophan: used for niacin (B3) synthesis
  • Proline: important for collagen production, aliphatic side chain
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13
Q

PTM: phosphorylation

A
  • happens on the OH side chains of serine, threonine and tyrosine in peptide chains
  • needs phosphate
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14
Q

Hydroxylation of lysine

A
  • produces hydroxylysine
  • copper dependent
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15
Q

hydroxylation of proline

A
  • makes hydroxyproline (Pro-OH)
  • vitamin C dependent
  • important in collagen subunits
  • associated with scurvy
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16
Q

PTM: gamma-carboxylation

A
  • vitamin K dependent
  • required for calcium homeostasis and blood clotting
  • another carboxyl group is added to glutamate to allow protein to bind to calcium
17
Q

PTM: iodination

A
  • crucial for the formation of thyroid hormones
  • crucial for regulation of metabolic rate
18
Q

PTM: ADP ribosylation

A
  • dependent on Niacin (vit B3)
  • adding ADP-ribose to an acceptor protein
  • when NAD+ is broken down in the cell, ADP-ribose and nicotinamide are the products
19
Q

Brief protein digestion

A
  • Mouth: no enzymatic breakdown, just mechanical
  • Stomach: HCl in gastric juice is released, denatures proteins and activates pepsin
  • Pancreas: pancreatic juice containing zymogens (inactive enzymes)
  • Small intestine: activates zymogens to produce small peptides and AAs
20
Q

protein digestion in the stomach

A
  • HCl is present in gastric juice, it denatures proteins and activates pepsin
  • pepsin is an endopeptidase - the first enzymatic part of breakdown
  • pepsin is secreted as pepsinogen (inactive) but is activated by HCl in the stomach
  • pepsin generates oligopeptides and some free AAs to be further digested in the SI
21
Q

protein digestion in the small intestine

A
  • trypsinogen travels from the pancreas and is converted to trypsin by enteropeptidase in the brush border
  • once activated, trypsin will activate all other zymogens
  • the enzymes breakdown oligopeptides from the stomach into free AAs and small peptides
22
Q

which part of the polypeptide chain does each intestinal enzyme attack

A

trypsin: basic AAs
elastase: neutral aliphatic AAs
pepsin and chymotrypsin: large neutral AAs
amino peptidase: removes N-terminal end
carboxypeptidase: removes C-terminal end

23
Q

AA absorption

A
  • most are absorbed by active transport
  • uses PEPT1 transporter - sodium dependent (indirect ATP requirement)
  • minor amount absorbed by facilitated diffusion
24
Q

Are all AAs absorbed the same?

A
  • essential AAs are absorbed faster than non-essential AAs
  • free AAs (supplements) have no advantage over food AAs
25
Q

what is glutamine used in intestine cells for

A
  • generate energy for the cell
  • stimulate cell proliferation
  • increase synthesis of Heat shock proteins
  • drive mucus production
26
Q

how does the liver use amino acids

A
  • uses 20% to make new proteins, enzymes and make peptide hormones
  • catabolizes the remaining 80% were NH3 is sent to the urea cycle and the carbon skeleton os sent to the Kreb’s cycle or used for gluconeogenesis or lipogenesis
27
Q

what is the basis of protein quality

A
  1. AA composition: more essential AAs = higher quality
  2. digestibility: more digestible = higher quality
  3. presence of toxic factors: less toxic factors = higher quality (e.g. soybeans contain inhibitors that interfere with trypsin thus preventing protein digestion)
  4. Species consuming the protein: ruminants have different needs than us because bacteria in the rumen can make all AAs
28
Q

Protein Efficiency ratio

A

Test - rats fed a diet with adequate nutrients except protein (10% kcal)
- pros: sensitive to AA balance, digestibility and toxic factors
- cons: don’t know WHY the protein is poor quality
PER = gain in body mass / total protein intake

29
Q

Chemical score (CS)

A

Test: test protein is digested into free AAs then quantified and compares to the AA composition of whole egg protein (perfect protein)
- whichever AA gives the lowest % (test/egg) is the CS
- pros: identifies limiting AA
- cons: doesn’t account for digestibility and toxins
CS = (amount of limiting AA in test protein/amount of same AA in egg) x 100

30
Q

Nitrogen balance

A

NB = N intake - N loss
- most people NB = 0
- if you don’t have enough protein NB < 0
- during growth and pregnancy NB > 0

31
Q

consequences of high protein diets

A
  • short term weight loss
  • improved insulin sensitivity compared to CHO diets
  • moderate increase in protein is cardio productive
  • high protein may be a concern longterm
32
Q

Marasmus

A
  • protein AND calorie deficiency
  • body switches to starvation mode
  • characterized by complete loss of body fat and muscle, peeling skin, uneven pigmentation
33
Q

Kwashiorkor

A
  • sufficient calories but very deficient in protein (1-2% protein)
  • comes with high CHO foods
  • characterized by enlarged abdomen, burns on skin and diarrhea
  • enlarged abdomen due to decreased plasma proteins causing osmotic imbalance (swelling of gut)
  • liver is enlarged due to inability to export fat from liver (can’t make VLDL)

NUTR 3210 (12 decks)

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