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Week 3 > Structure of Proteins 2 > Flashcards

Structure of Proteins 2 Flashcards

1
Q

what is tertiary structure?

A

the 3D folding of secondary structure

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2
Q

what are proteins organised into?

A

multiple domains

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3
Q

what does each domain of a protein do?

A

contributes a specific to the overall protein

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4
Q

loops and bends connect regions of…

A

alpha helices and beta sheets so that the polypeptide can fold into a globular domain

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5
Q

what 5 bonds can stabilise tertiary structures?

A

H bonds, van der waals, hydrophobic, ionic and disulphide bonds

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6
Q

how does a disulphide bond form?

A

the SH groups of 2 neighbouring cysteine residues form a covalent -s-s- bond releasing 2e- + 2H+

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7
Q

what is quaternary structure?

A

the association of more than one polypeptide

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8
Q

what can a quaternary structure complex be designated as?

A

an oligomeric protein

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9
Q

what often stabilises oligomeric structures?

A

disulphide bonds

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10
Q

how many different subunits does the 70S ribosome have?

A

around 30

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11
Q

what quaternary structure protein do many pharmaceutical drugs act upon and how many subunits does it have?

A

heterotrimeric G protein with 3 different subunits

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12
Q

give 2 examples of quaternary structure proteins that have identical subunits…

A

mechanosensitive conductance channel and stored insulin

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13
Q

what does haemoglobin do?

A

carries oxygen in red blood cells

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14
Q

what is another name for a red blood cell?

A

erythrocytes

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15
Q

what is the composition of haemoglobin?

A

symmetrical assembly of 2 alpha and 2 beta globin chains

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16
Q

what does each of the haemoglobin polypeptide chains contain?

A

a haem molecule

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17
Q

what does the haem molecule do?

A

binds oxygen for transport to tissues

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18
Q

what is the composition of haem?

A

iron 2+ in the centre surrounded by 4 N2 with a hydrophobic and hydrophilic end

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19
Q

what is each haem molecule held in place by?

A

hydrogen bonds from histidine F8 and the bound oxygen molecule stabilised by histidine E7

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20
Q

what kind of curve shows cooperative oxygen binding?

A

sigmoidal curve

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21
Q

the affinity in the first oxygen is low but…

A

binding of subsequent molecules is increased

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22
Q

why is the affinity for oxygen increased?

A

changes in protein structure as the first oxygen molecule binds

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23
Q

upon oxygen binding, the histidine that H bonds to the haem molecule in what helix changes position?

A

F (F8)

24
Q

biology significance of cooperativaty of oxygen molecules…

A

tight oxygen binding in the lungs and subsequent release in tissues where oxygen concentration is lower

25
Q

what is sickle cell anaemia caused by?

A

a single amino acid change at position 6 in the beat chain of haemoglobin

26
Q

what does hydrophilic glutamic acid mutate to in sickle cell anaemia?

A

hydrophobic valine

27
Q

why does the sickle cell anaemia mutation cause sickling?

A

due to aggregation of mutated haemoglobin that forms stiff fibres - change in the surface chemistry of the protein

28
Q

what is collagen?

A

a protein that helps bind cells together to form tissues

29
Q

how is collagen assembled?

A

in long, extremely strong fibres

30
Q

collagen is the chief protein of…

A

bone, tendon and skin

31
Q

collagen constitutes how much of the total protein mass in the body? (%)

A

25%

32
Q

what is the building block of collagen fibres?

A

tropocollagen

33
Q

what is the structure of tropocollagen?

A

3 polypeptide chains wound into a triple helix with a left hand twist and a right handed supercoil

34
Q

what is vital for the formation of tropocollagen and why?

A

glycine because it has a small side chain (only H)that allows tight turns

35
Q

how many residues per turn are there in tropocollagen?

A

3 amino acid residues

36
Q

what else is vital for the formation of Add to dictionary and why?

A

proline as it imposes the left hand twist in the helix that the main stabilising force of the unusual structure

37
Q

what do hydroxylated prolines become?

A

hydroxyproline

38
Q

what does hydroxyproline do?

A

forms strong hydrogen bonds that help to stabilise the triple helix

39
Q

what is the quarter-stagger model?

A

molecules are stitched together by covalent crosslinks and gaps provide access sites for lysyl oxidase

40
Q

what is deamination?

A

ammine group lost and replaced by O2

41
Q

lysine is deaminated by what and to form what?

A

lysyl oxidase to form aldehyde derivative

42
Q

aldehyde derivative is reactive or non-reactive?

A

reactive

43
Q

what does aldehyde derivative react with and to form what?

A

allysine to form aldol condensation product

44
Q

what is the brittle bone disease called?

A

osteogenesis imperfecta

45
Q

where is the mutation coding for osteogenesis imperfecta?

A

in the gene coding for one of the subunits leading to glycine being replaced by cysteine residue at one point in the chain

46
Q

how does the mutation in the gene coding for the glycine to cysteine change cause osteogenesis imperfecta?

A

the tropocollagen subunits cannot pack together properly and so there is a knock-on effect on collagen formation

47
Q

what are the symptoms of scurvy? (2)

A

dry skin, gum disorders

48
Q

what is the cause of scurvy?

A

lack of proline hydroxylation due to lack of vitamin C

49
Q

what are the symptoms of Ehlers-Danloss syndrome? (2)

A

loose skin, immobile joints

50
Q

what is the cause of Ehlers-Danloss syndrome?

A

lack of procollagen peptidase or lysyl oxidase

51
Q

how is strength built in at all levels in the collagen fibre? (4)

A

close packing of subunits, opposing twists of subunits and superhelix, hydrogen bonding, cross-linking

52
Q

how are the subunits of collagen closely packed?

A

glycine every 3rd residue

53
Q

what makes the twists of the subunits and superhelix opposite?

A

high proline content

54
Q

what forms strong hydrogen bonds?

A

hydroxyproline

55
Q

where is there cross linking?

A

between lysine-derived aldehydes

Week 3 (9 decks)

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