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Nutr 3210 > Lecture 8 - Proteins > Flashcards

Lecture 8 - Proteins Flashcards

1
Q

What is the 21st AA in humans that is not apart of the standard 20

A

selenocysteine

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2
Q

In humans, how many proteinogenic AAs are there

A

21

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3
Q

What is a proteinogenic AA

A

AA incorporated into protein during translation

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4
Q

What is an example of a non-proteinogenic AA

A

GABA (some neurotransmitters)

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5
Q

How many AAs are essential

A

9

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6
Q

What does it mean to be an essential AA

A

body cannot make it, must come from diet

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7
Q

What is the newest addition to the essential amino acids

A

histidine

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8
Q

What types of tissues have protein in the body

A

adipose tissue, blood, connective tissue, eye lens, skeletal muscle, cortical bone, and skin

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9
Q

What are the 3 main tissues in the body for protein location

A

blood (RBC), connective tissue, and the eye lens

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10
Q

What are enantiomers

A

D & L configurations, mirror images of one another

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11
Q

What are zwitterions

A

H transferred from COOH to NH2 in AA structure to make a negative COO- and positive NH3+, making a more polar structure

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12
Q

AAs are connected by ____________ bonds

A

peptide bonds

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13
Q

What is another term for peptide bond

A

amide bond

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14
Q

How do 2 AAs bond

A

carboxyl end of one reacts with amino group of another, releasing H2O as condensation and forming a peptide bond

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15
Q

What is the difference between the term polypeptide and protein

A

polypeptide = >50 AAs (long chain of amino acids)
more than 1 polypeptide = biologically active protein

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16
Q

What is primary structure

A

polypeptide chain of AAs held together by peptide bonds

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17
Q

What is secondary structure

A

hydrogen bonds that create a more stable structure of the polypeptide chain (think alpha helix and beta sheets)

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18
Q

What is tertiary structure

A

arrangement of secondary structure in 3D space

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19
Q

What is quaternary structure

A

combination of 2 or more tertiary structures required to make a functional protein

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20
Q

What is a native protein

A

normal 3D structure conformation

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21
Q

What is denatured protein

A

loss of bioactivity and conformation via pH, heat, detergents, etc.

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22
Q

What level of structure is not affected by denaturation

A

primary structure

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23
Q

What is a conditionally essential AA

A

not normally required in the diet in a healthy individual, but essential under certain contexts

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24
Q

What is an example of a genetic problem (from birth) that would result in a conditionally essential AA being essential

A

phenylketonuria: person is unable to breakdown Phe into Tyr (build up of Phe in the body causes mental defect)

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25
Q

What is a developed disease that would result in a conditionally essential AA being essential

A

liver disease that impairs Phe and Met catabolism (Tyr and Cys are synthesized from Phe and Met, so here Tyr and Cys are indispensable)

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26
Q

What are non-essential AAs

A

not needed in diet, completely synthesized in the body

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27
Q

What are 3 basic AAs

A

lysine, arginine, histidine

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28
Q

What are the characteristics of the basic AAs

A

polar
+ve charge on NH3 group enabling DNA binding

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29
Q

What are the characteristics of lysine

A

essential
simple straight chain
absent from grain products

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30
Q

What are the characteristics of arginine

A

non essential in healthy adults

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31
Q

What are characteristics of histidine

A

essential
ring structure
used to produce histamine

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32
Q

What are the 4 acidic AAs

A

aspartate, glutamate, asparagine, and glutamine

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33
Q

What are the characteristics of acidic AAs

A

polar
-ve charge on carboxyl side chain

34
Q

What are the characteristics of aspartate

A

non-essential
transmitted to oxaloacetate (Krebs)

35
Q

What are the characteristics of glutamate

A

non-essential
transmitted to a-ketogluterate (Krebs)
used to produce GABA

36
Q

What are the characteristics of asparagine

A

non-essential

37
Q

What are the characteristics of glutamine

A

non-essential
important in AA catabolism because it is a carrier of nitrogen

38
Q

What are the neutral AAs

A

glycine and alanine

39
Q

What are the characteristics of the neutral AAs

A

no charge, non-polar, aliphatic (C and H atoms join in straight or branched chains)

40
Q

What are the characteristics of glycine

A

non-essential
no enantiomers
used primarily to produce porphorin

41
Q

What are the characteristics of alanine

A

non-essential
important in AA catabolism because it is a carrier of nitrogen
important role in the glucose-alanine cycle

42
Q

What are some branched chain AAs

A

leucine, isoleucine, and valine

43
Q

What are the characteristics of branched chain AAs

A

neutral aliphatic, non-polar, all are branched, all are essential, not catabolized in the liver (high levels found in ciruclation)

44
Q

What AAs are found in high amounts in circulation and why

A

branched chain: not catabolized in liver, so lots is found in circulation

45
Q

What are the hydroxylated AAs

A

serine and threonine

46
Q

What are the characteristics of hydroxylated AAs

A

OH group on side chain is important for protein phosphorylation
polar

47
Q

What are the characteristics of serine

A

non-essential
OH group on side chain important for phosphorylation

48
Q

What are the characteristics of threonine

A

essential
OH group on side chain important for phosphorylation

49
Q

What are sulphur containing AAs

A

cysteine and methionine

50
Q

What are the characteristics of sulphur containing AAs

A

contain sulphur
non polar

51
Q

What are the characteristics of cysteine

A

non-essential
made from methionine
“spares” methionine when cysteine is consumed in the diet
used to form disulphide bonds
used in glutathione synthesis

52
Q

What are the characteristics of methionine

A

essential
methionine is limiting in legumes

53
Q

What are aromatic AAs

A

phenylalanine, tyrosine, tryptophan, and proline

54
Q

What are the characteristics of aromatic AAs

A

contain rings
non polar (except tyrosine)

55
Q

What are the characteristics of phenylalanine

A

essential
used to make tyrosine

56
Q

What are the characteristics of tyrosine

A

non-essential
“spares” Phe
used to synthesize neurotransmitters

57
Q

What are the characteristics of tryptophan

A

essential
used to make serotonin
used for niacin synthesis

58
Q

What are the characteristics of proline

A

non-essential
important for collagen production
aliphatic side chain

59
Q

What are the 9 essential amino acids

A

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

60
Q

Is there enzymatic break down of proteins in the mouth during digestion

A

no

61
Q

What breaks down proteins in the stomach

A

HCl in gastric juice
pepsin

62
Q

What does the pancreas have to do with protein break down

A

pancreatic juice used to digest proteins enzymatically

63
Q

What breaks down proteins in the small intestine

A

enzymes break down proteins, zymogens are active, and AAs are absorbed

64
Q

What cells secrete HCl in protein digestion in stomach

A

parietal cells

65
Q

What are the two functions of HCl

A

denature proteins
activate pepsin

66
Q

What bonds are disrupted in denaturing of protein

A

hydrogen bonds
electrostatic bonds

67
Q

Pepsin is secreted as _________________, which is an inactive zymogen

A

pepsinogen

68
Q

How does pepsinogen activate in HCl

A

since HCl is acidic, pepsinogen can activate as pepsin via conformational change (cannot do this in neutral pH)

69
Q

What is meant by pepsin is an endopeptidase

A

cleaves peptide bonds within a polypeptide chain

70
Q

What activates trypsinogen to trypsin in the small intestine

A

enteropeptidase enzyme in the brush border

71
Q

Activation of trypsin activates what other enzymes

A

chymotrypsin
elastase
carboxypeptidase

72
Q

What two ways are AAs absorbed in the small intestine

A

facilitated diffusion
active transport

73
Q

What are absorbed faster, essential or non essential AAs

A

essential

74
Q

Do free AAs have advantage for absorption over protein from foods

A

no

75
Q

What happens to proteins in terms of use

A

used for energy or synthesis of new proteins

76
Q

What is the function of glutamine in intestinal enterocytes

A

generate energy for the cell
stimulate cell proliferation
increase synthesis of heat shock proteins
drive mucus production

77
Q

Liver uses 20% of AAs to…

A

make new protiens/enzymes and make peptide hormones

78
Q

Liver uses 80% of AAs to…

A

catabolize them so NH3 is sent to urea cycle, carbon skeleton sent to Krebs for energy

79
Q

What are the 4 aspects to consider in protein quality

A

AA composition
digestibility
presence of toxic factors
species consuming the protein

80
Q
A

Nutr 3210 (9 decks)

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