Structure of Proteins 2

Question 1

what is tertiary structure?

Answer 1

the 3D folding of secondary structure

Question 2

what are proteins organised into?

Answer 2

multiple domains

Question 3

what does each domain of a protein do?

Answer 3

contributes a specific to the overall protein

Question 4

loops and bends connect regions of…

Answer 4

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

Question 5

what 5 bonds can stabilise tertiary structures?

Answer 5

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

Question 6

how does a disulphide bond form?

Answer 6

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

Question 7

what is quaternary structure?

Answer 7

the association of more than one polypeptide

Question 8

what can a quaternary structure complex be designated as?

Answer 8

an oligomeric protein

Question 9

what often stabilises oligomeric structures?

Answer 9

disulphide bonds

Question 10

how many different subunits does the 70S ribosome have?

Answer 10

around 30

Question 11

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

Answer 11

heterotrimeric G protein with 3 different subunits

Question 12

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

Answer 12

mechanosensitive conductance channel and stored insulin

Question 13

what does haemoglobin do?

Answer 13

carries oxygen in red blood cells

Question 14

what is another name for a red blood cell?

Answer 14

erythrocytes

Question 15

what is the composition of haemoglobin?

Answer 15

symmetrical assembly of 2 alpha and 2 beta globin chains

Question 16

what does each of the haemoglobin polypeptide chains contain?

Answer 16

a haem molecule

Question 17

what does the haem molecule do?

Answer 17

binds oxygen for transport to tissues

Question 18

what is the composition of haem?

Answer 18

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

Question 19

what is each haem molecule held in place by?

Answer 19

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

Question 20

what kind of curve shows cooperative oxygen binding?

Answer 20

sigmoidal curve

Question 21

the affinity in the first oxygen is low but…

Answer 21

binding of subsequent molecules is increased

Question 22

why is the affinity for oxygen increased?

Answer 22

changes in protein structure as the first oxygen molecule binds

Question 23

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

Answer 23

F (F8)

Question 24

biology significance of cooperativaty of oxygen molecules…

Answer 24

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

Question 25

what is sickle cell anaemia caused by?

Answer 25

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

Question 26

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

Answer 26

hydrophobic valine

Question 27

why does the sickle cell anaemia mutation cause sickling?

Answer 27

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

Question 28

what is collagen?

Answer 28

a protein that helps bind cells together to form tissues

Question 29

how is collagen assembled?

Answer 29

in long, extremely strong fibres

Question 30

collagen is the chief protein of...

Answer 30

bone, tendon and skin

Question 31

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

Answer 31

25%

Question 32

what is the building block of collagen fibres?

Answer 32

tropocollagen

Question 33

what is the structure of tropocollagen?

Answer 33

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

Question 34

what is vital for the formation of tropocollagen and why?

Answer 34

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

Question 35

how many residues per turn are there in tropocollagen?

Answer 35

3 amino acid residues

Question 36

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

Answer 36

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

Question 37

what do hydroxylated prolines become?

Answer 37

hydroxyproline

Question 38

what does hydroxyproline do?

Answer 38

forms strong hydrogen bonds that help to stabilise the triple helix

Question 39

what is the quarter-stagger model?

Answer 39

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

Question 40

what is deamination?

Answer 40

ammine group lost and replaced by O2

Question 41

lysine is deaminated by what and to form what?

Answer 41

lysyl oxidase to form aldehyde derivative

Question 42

aldehyde derivative is reactive or non-reactive?

Answer 42

reactive

Question 43

what does aldehyde derivative react with and to form what?

Answer 43

allysine to form aldol condensation product

Question 44

what is the brittle bone disease called?

Answer 44

osteogenesis imperfecta

Question 45

where is the mutation coding for osteogenesis imperfecta?

Answer 45

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

Question 46

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

Answer 46

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

Question 47

what are the symptoms of scurvy? (2)

Answer 47

dry skin, gum disorders

Question 48

what is the cause of scurvy?

Answer 48

lack of proline hydroxylation due to lack of vitamin C

Question 49

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

Answer 49

loose skin, immobile joints

Question 50

what is the cause of Ehlers-Danloss syndrome?

Answer 50

lack of procollagen peptidase or lysyl oxidase

Question 51

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

Answer 51

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

Question 52

how are the subunits of collagen closely packed?

Answer 52

glycine every 3rd residue

Question 53

what makes the twists of the subunits and superhelix opposite?

Answer 53

high proline content

Question 54

what forms strong hydrogen bonds?

Answer 54

hydroxyproline

Question 55

where is there cross linking?

Answer 55

between lysine-derived aldehydes