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b1.2 proteins Flashcards

1
Q

diagram of generic amino acid

A

amino grp
r grp
carboxyl grp
notes

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2
Q

why does R-group differ

A

differs in each of the 20 amino acids

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3
Q

polar

A

hydrophilic

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4
Q

non-polar

A

hydrophobic

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5
Q

formation of dipeptide

A

condensation

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6
Q

put water back in

A

hydrolysis

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7
Q

diagram of condensation

A
  • peptide bond formed
    notes
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8
Q

source of essential amino acids

A
  • must be obtained form the diet
  • cannot be synthesised by the body or other amino acids
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9
Q

source of non-essential amino acids

A

can be made form other amino acids

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10
Q

why does vegan diet require attention

A

ensure essential amino acids are consumed

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11
Q

why infinite variety of possible peptide chains

A
  1. 20 amino acids coded for in the genetic code
  2. peptide chains can have any number of amino acids
  3. amino acids can be in any order
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12
Q

polypeptide with 4 polypeptide chains

A

haemoglobin

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13
Q

protein denaturation by heat

A

increased kinetic energy and stronger vibrations that break intermolecular bonds

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14
Q

protein denaturation by pH

A

affects positive and negative charges on the R-groups of the amino acids, causing ionic bonds within protein to break
> changes 3d formation

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15
Q

denaturation

A

when the quaternary, tertiary, secondary structures are disturbed by external stress and results in a change in active site and loss of function

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16
Q

why is denaturation usually irreversible

A
  • very hard to reform the disulphide bond once its broken
    water has access to it and water wouldnt want it to fold back to its original shape
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17
Q

primary structure

A
  • order ofhow the amino acids are composed in the protein
  • formed by covalent peptide bonds between adjacent amino acids
  • controls all subsequent levels of structure
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18
Q

secondary structure

A
  • held by h bonds
  • alpha helix and beta sheets
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19
Q

tertiary structure

A
  • 3 dimensional bc of r group interactions
  • hydrophobic and hydrophilic side chains affecting the folding of the polypeptide
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20
Q

quaternary structure

A
  • made of more than one polypeptide chain
  • interaction between multiple polypeptides
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21
Q

what do R-groups determine

A

properties of assembled polypeptides

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22
Q

non-conjugated proteins egs [2]

A
  1. insulin
  2. collagen
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23
Q

conjugated protein eg [1]

A

haemoglobin

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24
Q

why does the structure have to be 3d

A

so hydrophobic elements would be protected inside

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25
Q

2 types of protein

A

fibrous or globular

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26
Q

fibrous protein eg

A

collagen

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27
Q

non-conjugated protein

A

only made up of polypeptides

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28
Q

conjugated proteins

A

has non-polypeptide component

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29
Q

polypeptide chains

A

separate chains held together using disulphide chains between R groups

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30
Q

difference between fibrous and globular proteins [5]

A

fibrous protein- have repeating sequence
shape: elongated and rounded in shape
fibrous proteins: do not (may have extended secondary structure)
globular proteins: tertiary structure
fibrous: insoluble
globular proteins: generally soluble

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31
Q

how does amine and carboxyl groups in R-groups become +ve or -ve charged

A

binding or dissociation of hydrogen ions- can participate in ionic bonding

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32
Q

what structure mediates and controls the formation of polypeptides

A

ribosome

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33
Q

how many natural amino acids are synthesised by ribosomes

A

none
- made into chains by ribosomes but amino acids not produced

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34
Q

3 examples of amino acids synthesised by ribosomes

A

collagen
enzymes
antibodies

35
Q

why is primary structure maintained after denaturation

A

energy was not enough to break the peptide bonds

36
Q

examples of what is broken during denaturation

A

disulphide bridges

37
Q

primary (polypeptide) fibrous or globular

A

neither (will fold to become later)

38
Q

secondary fibrous or globular

A

can be both

39
Q

tertiary fibrous or globular

A

can be both

40
Q

quaternary fibrous or globular

A

can be both

41
Q

what does amino acid sequence determine

A

the three-dimensional conformation of a protein

42
Q

what does a protein must consist of

A

single polypeptide or more than one polypeptide linked together

43
Q

what bonds do pairs of cysteines form

A

disulfide bonds

44
Q

how many molecules of water are required to completely hydrolyse a polypeptide made up of 23 amino acids

45
Q

3 eg of fibrous proteins

A

collagen, keratin, myosin

46
Q

2 eg of globular proteins

A

enzymes, antibodies

47
Q

characteristics of polar amino acids

A
  • soluble
  • stable interactions in water
  • strongly hydrophilic
48
Q

characteristics of non-polar amino acids

A
  • soluble
  • stable interactions in the lipid bilayer
  • hydrophobic
49
Q

where does process of forming dipeptide by condensation occur

50
Q

similarities of fibrous and globular protein [3]

A
  • polypeptides
  • chains of amino acids joined by peptide bonds
  • have primary structure
51
Q

non polar amino acids interactions w the membrane

A

retain protein in position in the membrane

52
Q

polar amino acids interaction w the membrane

A

form hydrophilic channels in the membrane

53
Q

where are polar amino acids on transmembrane proteins

A

on either side on the transmembrane protein

54
Q

proteins in the membrane + position/egs [8]

A
  1. peripherial proteins: on the surface
  2. some integral proteins (transmembrane proteins): extend from one side of the membrane to the other
  3. hormone binding sites: insulin
  4. enzymes: sucrase
  5. pumps for active transport
  6. electron carriers: etc
  7. neurotransmitters: acetylcholine
  8. pigments: in rods/cones
55
Q

how do non-polar amino acids help channel proteins + enzymes [2]

A
  1. help channel proteins + enzymes to be embedded in a membrane
  2. non-polar amino acids at active site attract non-polar substrate
56
Q

how do polar amino acids help channel proteins + enzymes [4]

A
  1. retain protein position in membrane
  2. lining pore allow polar particles to pass through
  3. on surface of enzyme allow it to dissolve in water
  4. active site of enzyme attract polar substrates
57
Q

how do polar + non-polar amino acids help enzymes

A

polar and non-polar amino acids contribute to the specificity of
an enzyme

58
Q

byproduct of condensation

59
Q

bond formed between sulphur-containing amino acids

A

disulphide bridges

60
Q

bond between r groups

A

ionic bond

61
Q

hydrophilic amino acid(s)

A

glutamic acid

62
Q

hydrophobic amino acid(s)

A

valine, cysteine, methlonine

63
Q

what bonds can be broken during denaturation

A
  1. hydrogen bonds
  2. disulphide bridges
64
Q

ribosomes

A

form dipeptide by condensation

65
Q

role of glycoproteins

A

recognise and bind to carbohydrate receptors on adjacent cells
> cell to cell attachment
> intracellular responses in the reacting cells

66
Q

glycoprotein eg

A

ABO antigens in blood

67
Q

haemoglobin (no. of polypeptides + type of protein)

A

4 polypeptides
globular protein

68
Q

how to calc no. of peptide bonds

A

no. of amino acids - no. of disulphide bridges

69
Q

products of condensation

A

dipeptide + h2o

70
Q

process of protein denaturation by heat

A

increase in kinetic energy → increase vibration → break bonds

71
Q

why is denaturation mostly irreversible

A

water has access to it → cant fold back to original shape

72
Q

definition of non-conjugated proteins

A

have components other than amino acids

73
Q

non-conjugated proteins eg [2]

A

collagen
insulin

74
Q

fibrous proteins eg [3]

A

collagen
keratin
myosin

75
Q

amino acids synthesised by ribosomes

A

collagen
antibodies
enzymes

76
Q

how are polypeptide chains held tgt

A

using disulphide bridges between R grps

77
Q

what does the positive or negative dissociation of H ions allow proteins to do

A

participate in ionic bonding

78
Q

bond between pairs of cystines

A

disulphide bonds

79
Q

similarities of fibrous + globular proteins

A
  • polypeptides
  • amino acids joined by peptide bonds
  • have primary structure
80
Q

y can amino acids dissolve in water

A

polar amino acids on the surface of enzymes

81
Q

function of polar amino proteins inside channel proteins

A

allow substances that are polar (eg. glucose, sodium ions) to pass through

82
Q

eg(s) of hydrophilic amino acids

A

glutamic acid

83
Q

eg(s) of hydrophobic amino acids

A

valine
cystine
methlonine

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