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Biochemistry > L3-4: Proteins in Health & Disease > Flashcards

L3-4: Proteins in Health & Disease Flashcards

1
Q

What does protein structure determine?

A

Interactions with other proteins, biomols and small molecules ie function

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2
Q

How were the first protein structures determined?

A

X-ray crystallography

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3
Q

What protein structure does myoglobin and haemoglobin have?

A

Myoglobin- tertiary
Haemoglobin- tertiary and quaternary

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4
Q

What does tertiary structure determine?

A

The overall 3D shape

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5
Q

What chunks do proteins fold in?

A

Domains

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6
Q

What is structural homology?

A

When related amino acid sequences give proteins very similar structures

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7
Q

Which programs can ‘guess’ structures of unknown proteins?

A

ML and LLM

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8
Q

What is quaternary structure?

A

Binding with other protein chains (homo/haem interactions) and binding to small molecules/metals/cofactors

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9
Q

What cofactor are myoglobin and haemoglobin associated with?

A

Haem

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10
Q

How are myoglobin and haemoglobin coordinated?

A

-Porphyrin ring with iron
-Globin protein coordinates iron axially
-‘free’ coordination space binds gases

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11
Q

What is the difference between myoglobin and haemoglobin?

A

Myoglobin- monomer
Haemoglobin- tetramer (2 alpha and 2 beta)

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12
Q

When does haemoglobin bind to oxygen in lungs and then release oxygen in muscles?

A

High pO2 in lungs
Low pO2 in tissues

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13
Q

What saturation curves do myoglobin and haemoglobin have?

A

Myoglobin = hill curve
Haemoglobin = sigmoid cure

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14
Q

When does myoglobin deliver oxygen?

A

Acts as a monomer to deliver in low oxygen saturation

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15
Q

How does oxygen bind to Haemoglobin?

A

subunits act cooperatively, affinity changes dependent on how much oxygen bound

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16
Q

What is allostery?

A

When binding at one site affects binding at another site

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17
Q

What factors can oxygen affinity in haemoglobin depend on?

A

-chloride ions
-Bis-phosphoglycerate
-Protonation state of haem
-CO2 binding

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18
Q

What is the cause of sickle cell?

A

It is autosomal recessive so it is inherited genetically

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19
Q

How is the sickle cell shape obtained?

A

Mutation in HbB gene (E6V), which causes loss of charge meaning haemoglobin polymerises at low pO2

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20
Q

How is CF caused?

A

Mutation in CFTR gene (Cystic Fibrosis Transmembrane conductance Regulator)

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21
Q

How does the mutation impact people with CF?

A

It impacts ATP-gated anion channel that regulates Cl- in epithelial tissues so the absence of affects the balance of ions in epithelial mucosa which can cause production of thick mucus in lungs

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22
Q

What is phenylketonuria?

A

The loss or poor function of phenylalanine hydroxylase enzyme

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23
Q

What happens when someone has phenylketonuria?

A

Excess phenylalanine isnt metabolised to tyrosine so there is competition for transporters meaning it outweighs levels of other amino acids which leads to deficiencies

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24
Q

How is phenylketonuria managed?

A

No treatment but is controlled by diet

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25
Q

What type of disease is type 1 diabetes?

A

Autoimmune disease

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26
Q

How is diabetes caused?

A

It is caused by the destruction of pancreatic beta cells which stops the production of insulin

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27
Q

What are the main side effects of diabetes?

A

Hypoglycemia
Sweats that can lead to seizures
Long term damage to blood vessels

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28
Q

What is insulin produced as?

A

110 AA preproinsulin in beta cells in pancreas

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29
Q

What is insulin stored as in the pancreas?

A

Zinc-coordinated hexamers in crystals

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30
Q

What does insulin do?

A

It binds to receptors which signals cells to produce and activate glucose transporters in fat and muscle cells, it also synthesises glycogen in the liver

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31
Q

How was insulin first produced to treat diabetes?

A

Using recombination therapies using E.coli

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32
Q

How can bleeding be stopped when a blood vessel is injured?

A

Clotting

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33
Q

How does a clot form?

A

Platelets aggregate to stop bleeding

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34
Q

What are the 2 different pathways of clotting cascades and what are the characteristics associated with them?

A

Intrinsic pathway: exposed endothelial collagen
Extrinsic pathway: tissue factor release

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35
Q

Which factors are proteases in blood clotting?

A

II, VII, IX, X, XI, XII

36
Q

What is Haemophilia A caused by?

A

An inherited deficiency of factor VIII

37
Q

What is haemophilia B caused by?

A

Deficiency of factor IX

38
Q

What is haemophilia C caused by?

A

Low levels of factor XI

39
Q

How is haemophilia inherited?

A

It is X-linked so most affected people are XY

40
Q

What are the symptoms of haemophilia?

A

Internal/external bleeding
Joint bleeding (causing permanent damage)

41
Q

What is the treatment of haemophilia?

A

Clotting factors from blood serum are used and they are produced in chinese hamster ovary cells

42
Q

What types of proteins are non-globular? give examples

A

Fibrous and filamentous proteins like cytoskeleton proteins
Structural proteins like keratin, silk and collagen

43
Q

What are features of globular proteins that assemble into fibrous quaternary aggrangements?

A

Strong
Dynamic
Can interact with other proteins and DNA

44
Q

What are characteristics of the cytoskeleton?

A

-Present in all cells
-links memb to nucleus in euks
-provides mechanical stability
-template for cell wall construction
-Dynamic network

45
Q

What are the key classes of the cytoskeleton?

A

Microfilaments (actin)
Intermediate filaments (vimentin and keratin)
Microtubules (tubulin)

46
Q

What are microfilaments primarily made up of?

A

Actin

47
Q

What is the function of actin in microfilaments?

A

Actin binds and hydrolyses ATP
(ATP-actin high affinity for other actin
ADP-actin low affinity)

48
Q

What ends is actin added to form microfilaments?

A

+ive end

49
Q

What are examples of function behaviour being key to function in microfilaments?

A

Profilin/gelsolin sequester free actin
Myosin motors bind to actin and move
Actin branching proteins allowing filaments to join
Capping proteins to stabilise ends

50
Q

How are intermediate filaments formed?

A

Coil-coiled proteins that may have globular ends at termini

51
Q

Where do intermediate filaments exist?

A

Mostly cytoplasm but some nuclear and extracellular

52
Q

What are the functions of intermediate filaments?

A

Cell adhesion
Cellular organisation
Muscle fibres

53
Q

What are the 6 types of intermediate filaments?

A

I&II- keratins
III-vimentin and desmin
IV- alpha-internexin and synemin
V- lamins
VI- nestin and filensin

54
Q

Where is alpha-keratin found?

A

Hair, nails, claws, feathers and skin

55
Q

What is the structure of keratin?

A

Coiled coil stabilised by hydrophobic interactions, disulphides and dimers that multimerise into tetramers

56
Q

What is the structure of vimentin?

A

Coiled coil, dimerises then forms anti-parallel tetramer, 8 form unit length filament forming fibrous filaments

57
Q

What is the key element of neurofilaments?

A

alpha-internexin/nestin

58
Q

What are the functions of lamins?

A

-Provides structure regulation of nucleus
-interacts with nuclear membrane
-sensitive to stretch

59
Q

What are microtubules made of?

A

Alpha and beta tubulin

60
Q

Where does elongation occur in microtubules?

A

At both ends (more rapid at +ive end)

61
Q

How are protofilaments formed?

A

By end-to-end tubulin polymerisation

62
Q

How are helical filaments formed in microtubules?

A

From 13 protofilaments

63
Q

Where are microtubules found?

A

Key component of cytoskeleton and organised and nucleated at micro-tubule organising centres (MTOC)

64
Q

What is a key place microtubules are found?

A

Centrosome

65
Q

What molecular motors are associated with microtubules?

A

Trafficking of vesicles in the cell
Endo/exocytosis
Dynein/Kinesin

66
Q

What are the proteins in myofibrils?

A

Actin, Myosin, Troponin, Tropomyosin, Titin

67
Q

What is the biggest protein?

A

Titin

68
Q

What are cilia made up of?

A

Complex microtubules

69
Q

What is the role of cilia?

A

Motility - epithelial cells that move mucus, there are sensory cilia in hair cells

70
Q

What are flagella? (How do they work in eukaryotes and prokaryotes?)

A

In eukaryotes they are similar to cilia and have a role in motility
In bacteria/archaea they are protein based helical filaments with motors connecting to cell membrane

71
Q

What are the properties of filamentous viruses?

A

They have globular capsid proteins that form helical filaments and they protect the genetic material in the helix structure

72
Q

What protein filaments can be found on surface of bacteria and archea?

A

Pilli and Fimbriae

73
Q

What is a pilus?

A

Conjugative appendage, transfers ssDNA into host cell (mechanism of ab resistance)

74
Q

What are fimbriae?

A

Surface attachments through adhesion on domains ends, role in biofilm formation

75
Q

What are curli fibres?

A

Amyloid fibres produced by enterobacteria, role in biofilm formation

76
Q

What structure does collagen have?

A

Triple helix:
2 identical a1 chains
3rd a2 with different seq
Rich in glycine, proline and hydroxyproline
Cross-linked:
Through condensation

77
Q

What is silk and what can it be produced by?

A

Fibrous protein:
Silkworm, Hymenopetra, spiders and lacewings

78
Q

What is silkworm silk made up of?

A

Fibroin:
Heavy & light variants
GSGAGA repeats (AAs)
Beta sheets
Disulphide links
Glycoprotein component
Sericin:
Serine rich
Beta sheet rich
H bonds to fibroin

79
Q

What are the different types of spider silk?

A

Ampullate, Flagelliform, Tubuliform, Aciniform and aggregate

80
Q

What are the mechanical properties of spider silk?

A

Strength as highly ductile and tensile strength
Dense

81
Q

What is the structure of spider silk?

A

Spidroin:
repetitive glycine and alanine rich
beta strands regions interspersed with disordered regions

82
Q

What are intrinsically disordered proteins?

A

Proteins that dont have regular tertiary structures (still stable and active)

83
Q

What diseases can be caused by protein misfolding?

A

Alzheimers, Parkinsons, ALS, CJD and type II diabetes

84
Q

What proteins are more susceptible to misfolding/aggregation?

A

Alpha-synuclein
Beta-amyloid
Prion

85
Q

What structure do amyloids have?

A

A distinct cross-beta-sheet arrangement

86
Q

How is BSE disease contracted?

A

Misfolding of the prion protein which has a role in memory

Biochemistry (10 decks)

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