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Biomolecules Of Life > Proteins & post-translational modifications > Flashcards

Proteins & post-translational modifications Flashcards

(50 cards)

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1
Q

Why is the polypeptide chain flexible yet conformationally restricted

A
  • shape of AA
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2
Q

Explain how the amino acid backbone is polarised

A

H - bonding

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3
Q

Define the alpha helix

A

spatial arrangement of AA near each other in the linear sequence

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4
Q

Describe the bonding of alpha helix

A
  • hydrogen bonding (making it polar)
  • regular right-handed helix (R groups stick outwards)
  • every 4th peptide amino group + carbonyl group align with each other
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5
Q

Why are RH helix more energetically favoured

A
  • proteins aim to get the lowest energy state
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6
Q

What are binding proteins

A
  • help DNA regulate cells reprocess including transcription
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7
Q

What is proline

A
  • stops the formation of alpha helix as no hydrogen atoms are bound to nitrogen
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8
Q

What are beta sheets

A

h-bonds between adjacent strands stabilising structures

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9
Q

Why is the antiparallel bonding more stable

A

h-bonding not distorted

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10
Q

What can be the shape of beta sheets due to the polypeptide backbone

A

they aren’t in one flat plane and are twisted

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11
Q

What is a function of beta sheets

A
  • it can create high tensile strength
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12
Q

Define the tertiary structures of proteins

A

spatial arrangemnt of AA usually far apart from each other in primary sequence

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13
Q

Define the quaternary structures of proteins

A

spatial arrangement of a protein made uno from more than 1 polypeptide

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14
Q

What do quaternary structures aid in

A

formation of larger proteins and structures

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15
Q

What is the allosteric effect

A

the binding of a ligand can affect the function or conformation of another protein

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16
Q

Define acetylation and the enzyme used in the process

A
  • addition of methyl group at the N-terminal AA (alpha)
  • acetyltransferases ( transfers acetyl form co-enzyme A)
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17
Q

What are the different types of acetylation

A
  1. N-terminal acetylation
  2. Histone acetylation
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18
Q

What is N-terminal acetylation

A
  • helps builds acetyl groups on on AA
  • protects from degradation and and increase the half life
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19
Q

What is histone acetylation

A
  • acetylation of lysine residues in histone proteins
  • reduces net +ve chsarge between histones and DNA leading to more open conformation and more transcriptional activity
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20
Q

What is histone deacetylases

A
  • remove modifications leading to closed nucleosome conformation with no transcriptional activity
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21
Q

Describe hydroxylation

Study These Flashcards
A
  • Addition of OH group
  • 2 residues are hydroxylated
    1. proline
    2. lysine
  • hydroxylation or organic compounds converts hydrophobic molecules into hydrophilic molecules
22
Q

Why is hydroxyproline important ion collagen

Study These Flashcards
A

involved in H-bonding of the collagen fibres aiding in structural stability

23
Q

What enzyme is needed to convert proline and name any additions

Study These Flashcards
A
  • propyl hydroxylase
  • ascorbic acid (vitamin C) as a cofactor
24
Q

Describe glycosylation and where does it take place

Study These Flashcards
A
  • attachment of sugar molecules to specific residues In proteins making them more soluble
  • lumen of ER and Golgi apparatus
25
What are the different types of glycoylstion
1. N-glycosylation 2. G - glycosylation
26
What is N -glycosylation
- Attachment of preformed complex carbohydrates (oligosaccharides) molecules to the nitrogen of an asparagine residue
27
What is G -glycosylation
- Attachment of sugar to O group of threonine and serine - no characteristic sequence involved
28
Describe phosphorylation
- a phosphate group derived form ATP is attached to proteins
29
What enzymes regulate phosphorylation
- kinases add - phosphatases remove
30
What re protein kinases
- highly selective targeting particular resides in certain proteins (no large scale activation)
31
Define protein cleavage
process by which specific peptide bond between AA residues are hydrolysed
32
What enzymes perfumes protein cleavage
proteases
33
What are the 3 groups proteases can fall under
1. Metalloproteases (contain metal ion) 2. Serine proteases (contain critical serine residues) 3. Aspartyl proteases (contains critical aspartic acid in active site)
34
Describe an example of Metalloproteases
Carboxypeptides - digestive enzyme found in gut - cleaves off last C-terminal residue from chain - functions between Val,Leu,Ile & Ala
35
Describe an example of Serine proteases
Chymotryposin - digestive enzyme found in gut - cleave peptide chain on the carboxyl Side of aromatic large hydrophobic residues
36
Describe an example of Aspartyl proteases
HIV protease - chop up remain soft polypeptide chinas that cleave itself out out of large chains produced from the viral genetic material
37
What are pre -proteins
38
What are pro-proteins
39
Describe the structure of keratin
- long - large proportion of sulphur and cysteine = disulphide bridges - tough
40
Explain the process of perming
- Ammonium thioglycolate reduces the disulphide links to thiol so the hair strands can be separated - curling reorients the strands and thiol group
41
Explain how to revert a perm back
- Neutraliser H2O2 - H2O2 oxidises some of the adjacent thiol groups to disulphide links to fix new orientation of the hair strands - it disrupts the weak bonds
42
Describe the structure of collagen
- long fibrous protein - triple superhelix (tropocollagen) - every 3rd AA is glycine
43
Describe the chemical components of collagen
- key AA = cysteine - no H-bonds within the strand instead between the strands - glycine is localised to the interior of helical bundles
44
What is osteogenesis the cause
- brittle bone disease - every 3rd AA in collagen is glycine
45
What are fibroblasts
collagne producing cells
46
Explain why we scar
collagen orientation in scars are parallel to epithelial surface unlike normal skin
47
Why is hydroxyproline essential in collagen
modifications of the proline residue increases the stability of the collagen triple helix
48
What does glycosylation of hydroxyproline in Y position do to the collagen molecule
makes the OH face outwards which is important for assembly, secretion and interactions
49
How is collagen further stabilised
- supported by chaperone proteins the collagen protein undergoes further processing and maturation in the Golgi apparatus
50
What does the N & C terminal cleavage result in with collagen
removes the signal peptide

Biomolecules Of Life (4 decks)

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