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

L3-4: Proteins in Health & Disease Flashcards

(86 cards)

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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
What type of disease is type 1 diabetes?
Autoimmune disease
26
How is diabetes caused?
It is caused by the destruction of pancreatic beta cells which stops the production of insulin
27
What are the main side effects of diabetes?
Hypoglycemia Sweats that can lead to seizures Long term damage to blood vessels
28
What is insulin produced as?
110 AA preproinsulin in beta cells in pancreas
29
What is insulin stored as in the pancreas?
Zinc-coordinated hexamers in crystals
30
What does insulin do?
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
31
How was insulin first produced to treat diabetes?
Using recombination therapies using E.coli
32
How can bleeding be stopped when a blood vessel is injured?
Clotting
33
How does a clot form?
Platelets aggregate to stop bleeding
34
What are the 2 different pathways of clotting cascades and what are the characteristics associated with them?
Intrinsic pathway: exposed endothelial collagen Extrinsic pathway: tissue factor release
35
Which factors are proteases in blood clotting?
II, VII, IX, X, XI, XII
36
What is Haemophilia A caused by?
An inherited deficiency of factor VIII
37
What is haemophilia B caused by?
Deficiency of factor IX
38
What is haemophilia C caused by?
Low levels of factor XI
39
How is haemophilia inherited?
It is X-linked so most affected people are XY
40
What are the symptoms of haemophilia?
Internal/external bleeding Joint bleeding (causing permanent damage)
41
What is the treatment of haemophilia?
Clotting factors from blood serum are used and they are produced in chinese hamster ovary cells
42
What types of proteins are non-globular? give examples
Fibrous and filamentous proteins like cytoskeleton proteins Structural proteins like keratin, silk and collagen
43
What are features of globular proteins that assemble into fibrous quaternary aggrangements?
Strong Dynamic Can interact with other proteins and DNA
44
What are characteristics of the cytoskeleton?
-Present in all cells -links memb to nucleus in euks -provides mechanical stability -template for cell wall construction -Dynamic network
45
What are the key classes of the cytoskeleton?
Microfilaments (actin) Intermediate filaments (vimentin and keratin) Microtubules (tubulin)
46
What are microfilaments primarily made up of?
Actin
47
What is the function of actin in microfilaments?
Actin binds and hydrolyses ATP (ATP-actin high affinity for other actin ADP-actin low affinity)
48
What ends is actin added to form microfilaments?
+ive end
49
What are examples of function behaviour being key to function in microfilaments?
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
How are intermediate filaments formed?
Coil-coiled proteins that may have globular ends at termini
51
Where do intermediate filaments exist?
Mostly cytoplasm but some nuclear and extracellular
52
What are the functions of intermediate filaments?
Cell adhesion Cellular organisation Muscle fibres
53
What are the 6 types of intermediate filaments?
I&II- keratins III-vimentin and desmin IV- alpha-internexin and synemin V- lamins VI- nestin and filensin
54
Where is alpha-keratin found?
Hair, nails, claws, feathers and skin
55
What is the structure of keratin?
Coiled coil stabilised by hydrophobic interactions, disulphides and dimers that multimerise into tetramers
56
What is the structure of vimentin?
Coiled coil, dimerises then forms anti-parallel tetramer, 8 form unit length filament forming fibrous filaments
57
What is the key element of neurofilaments?
alpha-internexin/nestin
58
What are the functions of lamins?
-Provides structure regulation of nucleus -interacts with nuclear membrane -sensitive to stretch
59
What are microtubules made of?
Alpha and beta tubulin
60
Where does elongation occur in microtubules?
At both ends (more rapid at +ive end)
61
How are protofilaments formed?
By end-to-end tubulin polymerisation
62
How are helical filaments formed in microtubules?
From 13 protofilaments
63
Where are microtubules found?
Key component of cytoskeleton and organised and nucleated at micro-tubule organising centres (MTOC)
64
What is a key place microtubules are found?
Centrosome
65
What molecular motors are associated with microtubules?
Trafficking of vesicles in the cell Endo/exocytosis Dynein/Kinesin
66
What are the proteins in myofibrils?
Actin, Myosin, Troponin, Tropomyosin, Titin
67
What is the biggest protein?
Titin
68
What are cilia made up of?
Complex microtubules
69
What is the role of cilia?
Motility - epithelial cells that move mucus, there are sensory cilia in hair cells
70
What are flagella? (How do they work in eukaryotes and prokaryotes?)
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
What are the properties of filamentous viruses?
They have globular capsid proteins that form helical filaments and they protect the genetic material in the helix structure
72
What protein filaments can be found on surface of bacteria and archea?
Pilli and Fimbriae
73
What is a pilus?
Conjugative appendage, transfers ssDNA into host cell (mechanism of ab resistance)
74
What are fimbriae?
Surface attachments through adhesion on domains ends, role in biofilm formation
75
What are curli fibres?
Amyloid fibres produced by enterobacteria, role in biofilm formation
76
What structure does collagen have?
Triple helix: 2 identical a1 chains 3rd a2 with different seq Rich in glycine, proline and hydroxyproline Cross-linked: Through condensation
77
What is silk and what can it be produced by?
Fibrous protein: Silkworm, Hymenopetra, spiders and lacewings
78
What is silkworm silk made up of?
Fibroin: Heavy & light variants GSGAGA repeats (AAs) Beta sheets Disulphide links Glycoprotein component Sericin: Serine rich Beta sheet rich H bonds to fibroin
79
What are the different types of spider silk?
Ampullate, Flagelliform, Tubuliform, Aciniform and aggregate
80
What are the mechanical properties of spider silk?
Strength as highly ductile and tensile strength Dense
81
What is the structure of spider silk?
Spidroin: repetitive glycine and alanine rich beta strands regions interspersed with disordered regions
82
What are intrinsically disordered proteins?
Proteins that dont have regular tertiary structures (still stable and active)
83
What diseases can be caused by protein misfolding?
Alzheimers, Parkinsons, ALS, CJD and type II diabetes
84
What proteins are more susceptible to misfolding/aggregation?
Alpha-synuclein Beta-amyloid Prion
85
What structure do amyloids have?
A distinct cross-beta-sheet arrangement
86
How is BSE disease contracted?
Misfolding of the prion protein which has a role in memory

Biochemistry (10 decks)

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