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NUTR 3210 > Lecture 9 - Protein Metabolism > Flashcards

Lecture 9 - Protein Metabolism Flashcards

1
Q

What are three functions of proteins?

A
  • provides AA for protein synthesis
  • source of energy (if needed)
  • substrate for glucose synthesis
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2
Q

What do we need from protein?

A

not the protein per se, but rather the AA in the protein

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3
Q

How many proteinogenic AA are there in humans?

A

21, all but selenocysteine are part of the genetic code

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4
Q

What is a proteinogenic AA?

A

refers to an AA that is incorporated into a protein during translation

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5
Q

What is the average protein percent consumption of daily calories in NA?

A

16%

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6
Q

What is health canada’s recommended protein intake?

A

10-30%

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7
Q

Are non-proteinogenic AA used to make protein?

A

no

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8
Q

How many AA are considered essential?

A

9

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9
Q

What is the water% of various tissues in the body?

A
  1. adipose - 30
  2. blood (RBC) - 64
  3. connective tissue - 60
  4. eye lens - 64
  5. skeletal mm - 74
  6. cortical bone - 12
  7. skin - 65
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10
Q

What is the lipid% of various tissues in the body?

A
  1. adipose - 62
  2. blood (RBC) - 0.5
  3. connective tissue - 1
  4. eye lens - 2
  5. skeletal mm - 4
  6. cortical bone - –
  7. skin - 10
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11
Q

What is the protein% for various tissues

A
  1. adipose - 8
  2. blood (RBC) - 35
  3. connective tissue - 37
  4. eye lens - 34
  5. skeletal mm - 20
  6. cortical bone - 25
  7. skin - 24
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12
Q

What is the % other of various tissues?

A
  1. adipose - –
  2. blood (RBC) - 0.1
  3. connective tissue - 0.9
  4. eye lens - –
  5. skeletal mm - 1
  6. cortical bone - 5
  7. skin - –
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13
Q

What %minerals are in various tissues?

A
  1. adipose - <0.1
  2. blood (RBC) - 0.4
  3. connective tissue - 1.1
  4. eye lens - <0.1
  5. skeletal mm - 1
  6. cortical bone - 58
  7. skin - 1
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14
Q

What is the whole body average percentage for water, fat, minerals protein and CHO?

A

water - 60%
fat - 20-25%
minerals - 2%
protein - 15%
CHO - 0.2%

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15
Q

do animal derived foods contain more protein than plant derived foods?

A

yes

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16
Q

What is the general structure of an AA?

A

Amino terminal - N
alpha carbon
side chain - variable composition
carboxyl terminal - COOH

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17
Q

What is the only thing in the amino acid structure that differs between AA?

A

the side chain

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18
Q

What are entantiomers?

A
  • mirror images
  • D vs L enantiomers
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19
Q

What AA exist as enantiomers?

A
  • all standard AA exist as enantiomers except for glycine
20
Q

Which enantiomer of AA is naturally occurring?

A

The L configuration
D configuration is made through post-translational modifications

21
Q

What are zwitterions?

A

a molecule or ion having separate positively and negatively charged groups
- for AA - the carboxyl group has a negative charge and the amine group has a positive charge, but resulting in a net charge of 0

22
Q

When are AA ionized?

A

at physiological pH
- protonated amine
- deprotonated carboxyl
- this increases polarity

23
Q

How are AAs connected?

A

peptide bonds (amide bonds)

24
Q

What type of bond is a peptide bond?

A

covalent

25
Q

How do AA form a peptide bond?

A

the carboxyl group of one AA reacts with amino group of another AA, releasing H2O (condensation reaction)

26
Q

How do you break a peptide bond?

A

add water

27
Q

What is the difference between a peptide and a protein?

A

A peptide has no function until it is folded into a 3D structure via chaperone proteins

28
Q

What is the primary protein structure?

A
  • determined by DNA sequence
  • polypeptide chain of AA
  • held together by peptide bonds (tln helped by chaperones)
  • polypeptide chain has a amino and carboxyl terminus
29
Q

What is the protein secondary structure?

A
  • bonds dont involve SC. only backbone
    two types
  • alpha helix: amino group makes a hydrogen bond with a carboxyl group 4 AA down the chain, creating a helical shape in the polypeptide
  • beta pleated sheets: an amino group makes a hydrogen bond with a carboxyl group in the folded back polypeptide chain, can be parallel or anti-parallel
30
Q

What are secondary structures determined by?

A

hydrogen bonds that create a more stable structure

31
Q

What are the proteins tertiary structure?

A
  • arrangement of the secondary structure in 3D space
  • one polypeptide chain
    involves interactions between AA S.C.
  • Hydrophobic AA are in the center and hydrophilic AA are on the outside
32
Q

What is the quaternary structure of proteins?

A
  • combination of 2+ tertiary structures
  • tertiary structures are called subunits
  • forms multi-subunit complex which contributes to the overall function of the protein
33
Q

What is a native vs denatured protein?

A

native - corresponds to the protein in its normal 3D conformation
denatured - when proteins unfold and therefore lose their function, loses its bioactivity

34
Q

How can proteins be denatured?

A
  • heat, salt, detergents, acidity
35
Q

What type of structures does denaturation effect?

A

2, 3, 4 but not 1

36
Q

How is the egg protein denatured?

A

egg protein is albumin
native albumin is transparent and liquid
when cooked, the albumin becomes opaque and hard - now denatured egg whites

37
Q

What are conditionally essential AA?

A

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

38
Q

What is phenylketonuria?

A

an inborn error of metabolism whereby a person is unable to breakdown phe into tyr
- a build-up of phe in the body causes intellectual disability
- the solution is to limit phe in the diet and supplement with tyr

39
Q

What is the relationship between liver disease and AA?

A

impairs phe and met catabolism
- tyr and cys are synthesized from phe and met respectively
- try and cys become indispensable in this context

40
Q

What are the 7 AA classifications?

A
  • basic
  • acidic
  • neutral
  • branched chain
  • hydroxylated
  • sulphur-containing
  • aromatic
41
Q

What are the basic AAs?

A
  • polar
  • basic aa (positive charge on NH3 group on s.c. enables DNA binding)
  • important in histone proteins, which interact with DNA
    Lysine - essential, simple straight chain, absent from grain products
    Arginine - non essential in healthy adults, absent in newborns, polar
    Histidine - essential, ring structure, used to produce histamine, basic, has immune function in children
42
Q

What are the acidic AAs?

A
  • acidic AA (-ve charge on side chain carboxyl group)
  • acidic AAs are polar
    Aspartate - non essential, transaminated to oxaloacetate (krebs), polar, protein catabolism
    Glutamate - non essential, transaminated to alpha ketoglutarate (krebs), used to produce GABA, polar, get rid of nitrogen groups in the body
    Asparagine - non essential
    Glutamine - non essential, important in AA catabolism because it is a carrier of nitrogen (to live/kidney), interorgan nitrogen transfer
  • aspartate and glutamate react with a basic amino group to produce neutral amides such as asparagine and glutamine
43
Q

What are neutral AAs?

A
  • no charge on s.c.
  • non polar
  • aliphatic (C and H atoms joined in straight or branched chains)
    Glycine - non essential, no enantiomers, used primarily to produce porphorin (component of heme, which is found in hemoglobin)
    Alanine - non essential, important in AA catabolism because it is a carrier of nitrogen (to liver/kidney), important role in the glucose alanine cycle
44
Q

What are branched chain AAs?

A
  • neutral aliphatic aa (no s.c. charge)
  • non polar
  • all are branched
    Leucine
    Isoleucine
    Valine
  • all are essential, not catabolized in the liver (no enzymes to break it down), so high levels found in circulation
45
Q

what are hydroxylated AAs?

A
  • OH group on s.c. is important for protein phosphorylation
  • polar AA
  • tyrosine can also be classified as hydroxylated but is group with aromatic AA
    Serine - non essential
    Threonine - essential
46
Q

What are sulfur-containing AAs?

A
  • contain a sulfur group
  • non polar
    Cysteine - non essential, made from methionine, spares methionine when cysteine consumed in the diet, used to form disulfide bonds, used in glutathione synthesis
    Methionine - essential, methionine is limiting in legumes, first step in the synthesis of all proteins
47
Q

What are aromatic AAs?

A
  • contain aromatic rings
  • non polar (except tyrosine because of OH group in its s.c.)
    Phenylalanine - essential, used to make tyrosine
    Tyrosine - non essential, spares phe, used to synthesize neurotransmitters
    Tryptophan - essential, used to make serotinin, used for niacin (B3) synthesis
    Proline - non essential, important for collagen production, aliphatic s.c., atypical ring, s.c. attached to backbone

NUTR 3210 (17 decks)

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