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Medical Cell Biology and Genetics > L1- Protein structure and function > Flashcards

L1- Protein structure and function Flashcards

1
Q

Proteins are macromolecules made of

A

amino acids

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2
Q

amino acids join…. to form a…..

A

amino acids join to form a polypeptide molecule

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3
Q

monomers join to form

A

polymers

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4
Q

amino acid sequence encoded by

A

gene

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5
Q

polypeptide chain folds into complex and highly specific three dimensional structure determined by

A

amino acids

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6
Q

folding depends on

A

chemical and physical properties of the amino acid

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7
Q

central dogma

A

DNA (transcription) –> RNA (translated) –> proteins

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8
Q

AA sequence pf protein encoded by

A

gene

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9
Q

Structure of amino acid

A
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10
Q

amino acids are classified accoring to

A

R group- changes chemical properties of AA ansd thereofr eth eprotein

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11
Q

when amino acids join together what is lost

A

water is lost- left with amino acid residues

(only amino acid residues in protien and not amino acid)

  • peptide bond
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12
Q

Ionisations state of amino acid

A
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13
Q

when you add solution to amino acid.. the amino group will

A

gain a hydrogen

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14
Q

when you add solution to amino acid.. the carboxylic acid will

A

lost a hydrogen

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15
Q

bases are

A

proton receivers- become positve

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16
Q

acids are

A

proton donors- become negative

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17
Q

amino acid residues are when the

A

amino and carboxyl group are lost- when AAs combine

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18
Q

pKa value

A

acid dissociation constant for weak acids e.g. amino acids

e.g. how likely the amino acid will ionise or dissociate (how acidic or basic the R group is

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19
Q

high pKa value

A

less likely to ionise

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20
Q

low pKa valie

A

more liekly to ionise

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21
Q

if the pH of the soljution is less (more acidic) than the Pk value then the group

A

will be protonated.

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22
Q

the R group can change the chemical properties e.g.

A

hydrophobic

hydrophilic

polar

non-polar

acidic

basic

neutral

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23
Q

if the pH of the solution is more (more alkali) than the pKa then the group

A

will be deprontonated

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24
Q

example of negatively charged R groups

A

e.g. lysine have a high PkR value

25
Q

positively charged R groups

A

e.g. glutamare have a lower PkR (aciddisociation of R group)

26
Q

at pH 7 (physiological) what will be the predominant form of asparate (pK=2.8)?

A

at pH 7 the equilibrium will move to the right due to the amino acid being deprontonated

27
Q

levels of protein structure

A

primary

secondary

tertiary

quaternary

28
Q

primary

A

linear amino acid sequence of the polypeptide chain

29
Q

secondary

A

local spatial arrnagment of the polypetide backbone

  • localised structre e.g. helices
30
Q

tertiary

A

final folded form

31
Q

quaternary

A

association between different polypeptides and proteins to form a multi subunit protein

32
Q

bond between two amino acids

A

peptide bond- loss of one water

33
Q

conformation of peptide bond can be

A

trans( alpha casrbons on oppsoite side of peptide bond) and cis (alpha carbon on same side of the peptide bond- steric clashes)

34
Q

bonds on either side of the eptide bond are free to

A

rotate- this define secondary structures

35
Q

amino acid R groups determine how…

A

the polpeptide folds and ultimately determine the physical natur eof proteins

36
Q

isoelectirc point of proteisn

A

pH at which there is no overall net charge- proteins ahve different isoelectric points

37
Q

basic proteins

A

pI (isoelectric point) >7 contain many positively charge amino

38
Q

acidic proteins have an isolectirc point

A

pI<7

contain many negatively (acidic) charged amino acids

39
Q

peptide bonds

A

planar bonds

  • alpha carbon, carbon, oxugen and hydrogen align in the same plan
  • rigid no roation
  • partial double bond
40
Q

if pH< pI is

A

protontated

41
Q

if pH >pI

A

is deprotonated

42
Q

size of peptides

A

a few amino acids in length

43
Q

size of polypeptides

A

many amino acids

44
Q

biologically active proteins come in a range of

A

sizes… average weight is 110

45
Q

protein conformation: sequences detmeines structure, structure determines….

A

function

46
Q

which bonds hold the primary structure togetrher

A

peptide bonds

47
Q

types of secondary structure

A
  1. alpha helix
  2. Beta sheet
48
Q

alpha helix structure

A

3.6 aa. turn, 0.54 nm pitch and right handed

49
Q

what bonds stabilise the structure of the alpha helix

A

H bonds run up and down the chain- no othe rbonds holding together

–> backdon of C=O group of one residue is H bonded to the NH group of the residue 4 amino acids away

50
Q

B-strand also known as

A

the extended conformation

51
Q

B-strand/sheet condormation

A
  • Sheets of of polypeptides held together by H bonds above and below
  • R groups alternate between opposite sides of chain
52
Q

types of B-sheet

A
  • antiparallel- adjacent B-strand srun in opp directions with muiltiple H bonds stabiolising the strcuture
  • parallel- run in same direction
  • mixed- run in mixed direction
53
Q

tertiary structure

A

when primary and secondary strucutres come together e.g. globular and fibrous protein

54
Q

fibrous protein

A

a lot of very simple repeating secondary structure- supportive structure e.g. collagen

Role: support , shape, protect 


Long strands or sheets 


Single type of repeating secondary structure 


55
Q

Globular protein

A

lots of mixed conformation- have many structures e.g. enzymes and transporter molecules e.g. carbonic anhydrase 


Role: catalysis, regulation 


Compact shape 


Several types of secondary structure


56
Q

domains

A

part of polypeptide chain that fold into a distinct shape- often a speciifc functional role

57
Q

folding of membrane protein

A

Polypeptide chains fold to so that hydrophobic side chains are buried and polar, charged chains are on the surface e.g. myoglobin

• Membrane proteins often show “inside out” distribution of amino acids

58
Q

Quarternary structure

A

multi-subinit proteins e.g. haemoglobin e.g. ribosomes

Medical Cell Biology and Genetics (33 decks)

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