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Nutrition and Metabolism > Protein and Amino acid Metabolism and requirements > Flashcards

Protein and Amino acid Metabolism and requirements Flashcards

1
Q

What amino acids are a precursor of signal transducer?

A

arginine for nitric oxide synthesis

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2
Q

what are amino acids?

A

building blocks of protein

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3
Q

What elements do the amino acid structure contain?

A

carbon, hydrogen, oxygen, nitrogen and some cases, sulfur.

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4
Q

what is the structure of amino acid made of?

A

α-amino group, α-carboxyl group (acid group) and a side R-chain

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5
Q

what is aspartame?

A

artificial sweetener

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6
Q

Which combination of aspartame L and D configurations cause sweet taste?

A

L and L

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7
Q

Which combination of aspartame L and D configurations cause bitter taste?

A

D and L
L and D
D and D

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8
Q

The amino acid structure give it its properties, what type of properties are there?

A
  • non-polar
  • polar
  • positive charge
  • negative charge
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9
Q

What happens in condensation?

A

loss of H2O

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10
Q

What are polypeptide chains?

A
  • chains of amino acid
  • proteins made of many polypeptides
  • have peptide linkages
  • amine-carboxyl group linakge with condensation of H2O
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11
Q

What are the causes of protein degradation to amino acids?

A
  1. Abnormal proteins (mutant/damaged)
  2. Short-lived proteins (regulatory proteins/rate-limiting enzymes)
  3. Long-lived normal proteins (contractile proteins in muscle)
  4. Membrane proteins (e.g. receptors)
  5. Endocytose proteins (plasma proteins, hormones, lipoproteins)
  6. Mitochondrial proteins
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12
Q

What are the 3 pathways of protein degradation to amino acids?

A
  • ubiquitin-proteasome pathway
  • lysosomes
  • mitochondrial proteases
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13
Q

What switches on the proteasomal pathway?

A

acidosis in muscle of patients with renal failure

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14
Q

What are the 2 stages in the proteosomal pathway when activated?

A
  1. Ubiquitin tagging

2. Proteolytic degradation

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15
Q

What are important regulators of protein metabolism?

A
  • FOXO1
  • Smad
  • Akt (protein kinase B)
  • mTOR
  • 4EBP1
  • p70S6K
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16
Q

What is FOXO1?

A

transcription factor

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17
Q

What is Smad?

A

signal transducer

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18
Q

What is Akt (protein kinase B)?

A

protein kinase which decrease apoptosis and increase protein synthesis

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19
Q

what is mTOR?

A

protein kinase that regulates cellular processes

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20
Q

what stimulates mTOR?

A

leucine metabolite α-ketoisocaproate

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21
Q

What is 4EBP1?

A

binds to elF4E (eukaryotic translation initiation factor 4E) and stops initiation

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22
Q

what is p70S6K?

A

increase protein synthesis

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23
Q

Name the levels of protein structure and what each structure is defined as:

A

primary = amino acid sequence

secondary = α helices, β sheet

tertiary = folded, compact with van der Waals forces and disulphide bridges

quatermary = non-covalent associate of polypetide chains, non-covalent hydrogen bonds/van der Waals forces

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24
Q

What percentage of the protein is in the muscle, skin, bones and the remainder?

A 
muscle = 50%
bone = 20%
skin = 10%
others = 20%
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25
Q

How many proteins are there in the body on a range?

A

30,000-50,000 proteins

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26
Q

What can all tissues do regarding non-essential amino acids?

A
  • all can make non-AA
  • remodel the mix of amino acids
  • convert non-AA carbon skeletons into amino acids/other derivatives that have nitrogen
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27
Q

Which organ is the major site of nitrogen metabolism?

A

liver

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28
Q

when in dietary surplus, potentially toxic nitrogen of amino acids is eliminated via?

A
  • transaminations
  • deaminations
  • urea formation
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29
Q

What are carbon skeletons generally conserved as?

A
  • carbohydrate, via gluconeogenesis

- fatty acid, via fatty acid synthesis pathways

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30
Q

What are some 3 essential amino acids?

A

Arginine
Methionine
Phenylalanine

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31
Q

What is arginine and what is it needed for?

A

synthesised by mammalian cells, but rate insufficient to meet growth needs

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32
Q

what is methionine needed for?

A

large amounts to produce cysteine if insufficient in diet

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33
Q

what is phenylalanine needed for?

A

large amounts to form tyrosine, if not adequately supplied in diet

34
Q

What two amino acids are conditionally essential, and what are they needed for?

A 
arginine = essential in preterm infant
glutamine = trauma, cancer
35
Q

What happens in a diet low in lysine?

A

lead to incomplete protein synthesis

36
Q

What is the limiting amino acid in wheat protein?

A

lysine

37
Q

What is the limiting amino acid in maize protein?

A

tryptophan

38
Q

What is the limiting amino acids in beef protein?

A

methionine, cysteine

39
Q

Among vegetable proteins, which has the most complete amino acids?

A

soya protein

40
Q

What is PDCAAS?

A

Protein digestibility corrected amino acid score

41
Q

How do you calculate PDCAAS?

A
  1. Analyse nitrogen content
  2. calculate protein (N x 6.25)
  3. Analyse essential amino acid (IAA) content
  4. Calculate amino acid score (uncorrected)
  5. Determine digestibility
  6. Calculate PDCAAS
42
Q

What is the formula for the amino acid score?

A

mg of EAA in 1g test protein DIVIDED by mg of EAA in 1g amino acid reference pattern

43
Q

what is the PDCAAS formula?

A

= lowest uncorrect EAA ratio MULTIPLIED by true protein digestibility

44
Q

What is the first step of amino acid catabolism?

A

removal of nitrogen containing amino group

45
Q

removal of amino groups of 20 amino acids begins with?

A

transfer of groups to glutamic acid

46
Q

What facilitates/catalyses amino acid transfer to glutamate, and what is the process called?

A

glutamate dehydrogenase

called “oxidative deamination”

47
Q

what are the products of amino acid catabolism?

A

alpha-ketoglutarate and ammonium ion (NH4+)

48
Q

What is the remainder of the carbon skeleton converted to?

A
  • acetyl-coA
  • pyruvate
  • citric acid cycle intermediate
49
Q

What are the 3 categories that amino acids fall into?

A
  • glucogenic
  • ketogenic
  • glucogenic and ketogenic
50
Q

What are the amino acids that are both glucogenic and ketogenic?

A

(remember ‘PiTTT’)

  • phenylalanin
  • isoleucine
  • threonine
  • tryptophan
  • tyrosine
51
Q

What are the amino acids that are only ketogenic?

A
  • lysine

- leucine

52
Q

What is the carbon skeleton remnant of ketogenic/lipogenic amino acids?

A

acetyl coA

53
Q

What is the carbon skeleton remnant of glucogenic amino acids?

A

pyruvate, TCA cycle intermediate

54
Q

What is the metabolic fate of ketogenic/lipogenic amino acids?

A

TCA cycle, energy production, ketogenesis, lipogenesis

55
Q

What is the metabolic fate of glucogenic amino acids?

A

TCA cycle, energy production, gluconeogenesis

56
Q

What does the greek word “anaplerosis” mean?

A

fill up

57
Q

What does the greek word “cataplerosis” mean?

A

drain out

58
Q

What is the sole purpose of the urea cycle?

A

remove ammonia from body

59
Q

how much % of free ammonia at physiological pH?

A

1%

60
Q

What are the dangers of ammonium salts?

A
  • toxic
  • causes vomiting
  • convulsions
  • ultimately coma and death
61
Q

At what levels of ammonium ion concentration, would it lead to coma and death?

A

exceeding 250µM.

62
Q

What ions do ammonium ions mimic?

A

potassium ions

63
Q

What do ammonium ions possibly favour?

A

synthesis of excessive amounts of glutamate and glutamine = have excitatory effects on neural tissues

64
Q

What is required for removal of urea via kidneys?

A

urea is soluble but requires appreciable quantities of water

65
Q

What happens when cytosolic arginine is cleaved?

A

cleaved by arginase to urea and ornithine

66
Q

How is citrulline formed in the urea cycle?

A
  • cytosolic ornithine moves to mitochondrial matrix

- condensed with carbamoyl phosphate

67
Q

What provides the urea cycle reaction its energy?

A

anhydride of carbamoyl phosphate

68
Q

Where is citrulline transported to?

A

cytosol

69
Q

Where are the two locations of urea cycle?

A

mitochondria and cytosol

70
Q

What happens as a result of humans not being able to tolerate high concentrations of essential amino acids?

A

if not deposited as protein, they are oxidised by high-capacity, highly regulated oxidative pathways

71
Q

what is the anabolic drive?

A

essential amino acids regulate protein synthesis and protein degradation

72
Q

What are the 5 categories of nutrition disorders and nutrition related conditions?

A
  1. Malnourishment/undernourishment
  2. Sarcopenia/frailty
  3. Overweight/obesity
  4. Micronutrient abnormalities
  5. Re-feeding syndrome
73
Q

Under the malnourishment tree, what are some examples of ‘disease-related malnutrition (DRM) without inflammation’ diseases?

A
  • stroke
  • dementia
  • parkinson’s disease
  • anorexia nervosa
  • depression
  • malabsorption (coeliac disease, short bowel syndrome)
74
Q

How do you measure protein requirements via looking at muscle loss/gain?

A

anthropometry, MRI

75
Q

How do you measure protein requirements via looking at nitrogen balance?

A

collect food/urine/faeces

76
Q

How do you measure protein requirements via looking at protein turnover?

A

isotopic methods

77
Q

What is positive nitrogen balance?

A

intake of N > total N output

78
Q

What is negative nitrogen balance?

A

intake of N < total N output

79
Q

What are some examples of excreted nitrogen compounds?

A

urea, bacterial protein, ammonia

uric acid, urea, creatinine, protein

80
Q

required balance of nitrogen intake is?

A

5mg N/kg/day

81
Q

Is less or more protein needed for pregnant women?

A

less

82
Q

Who may need more protein requirements?

A
  • patients with renal failure
  • older people
  • obese undergoing weight-loss therapy

Nutrition and Metabolism (14 decks)

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