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FBS1 > Cell Biology and Signalling > Flashcards

Cell Biology and Signalling Flashcards

1
Q

What are bacterial cell walls made from?

A

Peptidoglycan

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2
Q

Which has an antagonist action to adenylate cyclase?

A

Phosphodiesterase

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3
Q

Alpha helices and beta sheets are formed by which type of bonding?

A

Hydrogen

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4
Q

What is Km a measure of and what does a lower value indicate?

A

Enzyme performance

Higher affinity

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5
Q

Where does ATP production occur in:

a) Prokaryotes
b) Eukaryotes

A

a) Cell membrane

b) Mitochondria

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6
Q

What three elements is the cytoskeleton made up of?

A

Actin
Microtubules
Intermediate filaments

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7
Q

3 functions of SER?

A

N linked glycosylation
Detoxification of xenobiotics
Biosynthesis of membrane lipids + steroids

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8
Q

Two functions of RER?

A

Proteins for secretion/ insertion go to cell membrane

Proteins folded, cys-cys bridge formed

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9
Q

4 functions of Golgi apparatus?

A

Glycosylation of carbohydrates and lipids
Synthesise lysosomes
Synthesise + package material to be secreted
Direct proteins to correct compartments

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10
Q

4 functions of peroxisomes?

A

Detoxification of toxins, alchol, FA
Phospholipid synthesis
Oxidation of VLCFA
Enzymes that synthesise and degrade H2O2

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11
Q

What causes Zellweger syndrome?

A

Inherited absence of peroxisomes due to defects in targeting

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12
Q

What causes adrenoleukodystrophy (ALD)?

A

Affects proteins that imports VLCFA into peroxisomes

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13
Q

What is autophagy?

A

Organelle turnover/replacement

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14
Q

Myoclonic epilepsy with Ragged Red Fibre (MERRF Syndrome)?

A

Mutation of mitochondrial gene for tRNA-lys

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15
Q

Hutchinson - Gilford Progeria?

A

Mutation in lamin - A prt of nuclear envelope
Distorted shape of nucleus (blebbed)
Production of unique progerin protein

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16
Q

Tay-Sachs disease?

A

Mutation of lysosomal hexosaminidase A enzyme

Causes accumulation of neurotoxic ganglioside

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17
Q

What are operons (in bacteria)?

A

Functional units of DNA containing cluster of genes under control of a single promoter

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18
Q

What are 6 types of enzymes and their functions

A

Oxidoreductases- catalyse transfer of hydrogen + electrons
Transferases - catalyze transfer of functional groups between molecules
Lyases - cleavage of C-C, C-O, C-N, addition to /formation of double bonds
Hydrolases - cleavage of bonds by addition of H2O
Isomerases - transfer of functional groups within same molecule
Ligases - catalyse formation of new covalent bonds using ATP, repair DNA breakage

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19
Q

Soluble vs Membrane protein?

A

Soluble - in cytosol, hydrophobic core, hydrophilic surface

Membrane - embedded in membrane, hydrophobic surface

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20
Q

What type of enzyme is chymotrypsin and what does it affect?

A

Hydrolase
Cleaves peptide bond on carboxyl side of tryptophan, tyrosine, phenylalanine and large hydrophobic residues e.g. methionine

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21
Q

What makes up chymotrypsin catalytic triad?

A

Serine
Histidine
Arginine

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22
Q

3 assumptions about Michaelis-Menton plot?

A

[S]&raquo_space;[E]
[ES] x change with time (steady - state, made at same rate as broken down)
Initial velocities used, [product] small, back reaction of P to S ignored

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23
Q

What is Michael - Menton equation?

A

V0= Vmax[S] /Km + [S]

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24
Q

Equation for Km?

A

K2+ K-1/K1

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25
Q

Defintion of Kcat?

A

No. of substrate molecules converted to product in a given unit of time on a single enzyme molecule when enzyme saturated with substrate

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26
Q

Lineweaver- Burke Plot equation?

A

1/V0= Km/Vmax 1/[S] + 1/Vmax

-1/Km is x-intercept, always -ve

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27
Q

How does a competitive inhibitor affect:

a) Michaelis-Menten plot?
b) Lineweaver-Burke plot?

A

a) Vmax same, Km increases and becomes Kapp (apparent)

b) Kapp increases so x-axis intercept decreases (mehr -ve)

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28
Q

How does a non-competitive inhibitor affect:

a) Michaelis-Menten plot?
b) Lineweaver-Burke plot?

A

a) x affect Km but Vmax smaller

b) Y-intercept increase, x-intercept same

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29
Q

What type of curve do allosteric enzymes show?

A

Sigmoid curve

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30
Q

Where are hydrogen bonds formed in alpha helix?

A

Between peptide bond carbonyl O and H of N-H every 4th peptide

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31
Q

How many residues per turn in an alpha helix?

A

3.6

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32
Q

How are the r groups in a beta pleated sheet arranged?

A

Trans position

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33
Q

What are the 2 types of beta pleated sheet and 1 feature of each?

A

Antiparallel - hairpin bend, widespread globular proteins

Parallel - arrows point to C terminus

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34
Q

What is the AA change in sickle cell and why is it significant?

A

Glut ==> Val

Hydrophillic to hydrophobic

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35
Q

What is phenylketonuria?

A

Defective phenylalanin hydroxylase (phe==>tyr)

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36
Q

What is main cause of albinism?

A

Defective tyrosinase (tyr ==> melanin)

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37
Q

What is molecular weight of water?

A

18g

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38
Q

What is Henderson-Hasselbach equation?

A

pH = pKa + log[A-]/[HA]

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39
Q

What is the physiological buffer in:

a) Saliva?
b) Blood?
c) Urine?

A

a) Bicarbonate
b) Haemoglobin
c) Phosphate

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40
Q

What are the common head groups found in glycophospholipids?

A

Choline, Serine, Ethanolamine, Inositol

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41
Q

What is characteristic of sphingomyelin?

A

No glycerol backbone, has single FA tail

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42
Q

What is significant about the arrangement of the positioning of the different glycophospholipids in the lipid bilayer?

A

Phosphotidylcholine and sphingomyelin face extracellular environment
Phosophotidylserine and phosphotidylethanolamine face cytosolic side

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43
Q

What is the equation for the hyperbolic curve of myoglobin?

A

Yo2 = Po2/P50 + PO2

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44
Q

What are the chains in adult haemoglobin and foetal haemoglobin?

A

Alpha 2, Beta 2

Alpha 2, Gamma 2

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45
Q

What state does Hb have to be for BPG to be able to bind?

A

T state

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46
Q

What is BGP?

A

2-3-bisphosphate glycerate

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47
Q

Why is BGP induced stabilisation of T-state less efficient in Hbf?

A

Gamma chain has a H143S mutation, so it has a higher O2 affinity which is useful for the foetus

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48
Q

In what state does Hbs have to be so that aggregation is less likely to form?

A

R state (oxygenated)

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49
Q

What region of the Golgi apparatus faces:

a) ER?
b) Membrane?

A

a) Cis region

b) Trans region

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50
Q

How are proteins targeted to mitochondria?

A

Complexed with chaperones

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51
Q

When proteins are targeted to the mitochondria, are they folded or unfolded?

A

Unfolded

52
Q

How are proteins targeted to the nucleus?

A

Nuclear proteins contain nuclear localisation signal (NLS)

53
Q

What does NLS bind to when
a) entering
b) leaving
nucleus via nuclear pore?

A

Importin and exportin

54
Q

How are proteins targeted to lysosomes?

A

Lysosomal proteins are tagged with mannose 6-phosphate in the Golgi apparatus

55
Q

What is inclusion cell disease?

A

The specific receptor that recognises mannose which targets vesicles to become lysosomes is faulty

56
Q

What is mutant N-acetylglucosamine-1-phosphotransferase enzyme?

A

Doesn’t tag proteins with mannose 6 phosphate so they don’t reach lysosme
Lysosomes don’t form

57
Q

What are the size of actin microfilaments and and what are their polymers?

A

7-9 nm in diameter

Actin

58
Q

What are the size of intermediate filaments?

A

10nm

59
Q

What are the size of microtubules and what are their polymers?

A

25nm

Tubulin

60
Q

What is the monomer of actin?

A

G actin

61
Q

What is the orientation of g-actin when it polymerises to f-actin?

A

Head to tail orientation
Each microfilament has a + and - end
Monomers can be added to either end

62
Q

4 functions of actin?

A

Muscle contraction
Mechanical support
Maintaining cell shape
Cell movement

63
Q

What type of G actin binding protein is present in actin?

A

Thymosin beta 4 - inhibits polymerisation

64
Q

What type of cross-linking proteins are present in actin?

A

Villin - parallel bundles in microvilli

Filamen - joining at angles to create a mesh

65
Q

What type of severing proteins are present in actin?

A

Gelsolin - cuts and binds to + end

66
Q

What is cytokinesis?

A

Ring of actin forms in the centre of cells
Anchors to plasma membrane
Myosin contraction constricts cells

67
Q

Examples of intermediate filaments in:

a) Epithelial cells?
b) Axons?
c) Universal (nuclei)?

A

a) Keratin
b) Neurofilamen
c) Lamins A, B, C

68
Q

What is epidermolysin bullosa simplex?

A

Mutations in keratin resulting in skin blistering disease

69
Q

What is amyotrophic later sclerosis (ALS)?

A

Abnormal expression of neurofilamens resulting in a neurodegenerative disease

70
Q

What is a microtubule organising centre (MTOC)?

A

Core from which microfilaments grow out of

Grow out until they reach destination then stabilized

71
Q

5 functions of microtubules?

A 
Dynamic scaffold 
Movement of cargo to specific locations in cell 
Central internal support of cilia 
Stabilise structure of cells 
Organise structure of organelles
72
Q

What is the difference between kinetochore and aster microtubules?

A

Kinetochore attaches to centromere of chromatids

Aster attaches centromere to cell membrane

73
Q

What are the two motor proteins associated with microtubules?

A

Kinesin and Dynein

74
Q

What direction to kinesin and dynein move towards?

A

Kinesin move towards + end, towards cell peripherary

Dynein moves towards - end, near nucleus

75
Q

What is the MTOC of cilia?

A

Basal body

76
Q

What are the two types of cilia and where are they found?

A

Stereocilia - inner ear

Motile cilia - lung

77
Q

What is Situs Inversus?

A

Organs in mirrored position, caused by defect in cilia mediated movement of growth factors in embryo

78
Q

What disease is caused by a mutated protein associated with abnormal function of primary cilia?

A

Autosomal dominate polycystic kidney disease

79
Q

Where are these glc transporters found?

a) GLUT 1
b) GLUT 2
c) GLUT 3
d) GLUT 4

A

a) Ubiquitous
b) Liver, pancreatic beta cells
c) Neurones
d) Muscles, adipocytes

80
Q

Which GLUT receptor is regulated by insulin?

A

GLUT 4

81
Q

What does SGLUT transport?

A

Na and glc symport

82
Q

What does phosphorylation of Na-K pump cause?

A

Conformational change that closes cytoplasmic access and opens external acess
Releases Na outside cell

83
Q

What does hydrolysis of the phosphate group in the Na - K pump cause?

A

Opens cytoplasmic access and releases K into cell

84
Q

The mutation in what protein causes cystic fibrosis?

A

Cystic fibrosis transmembrane conductance regulator protein

85
Q

Five factors that act as extracellular signals?

A 
AA and derivatives 
Steroids 
Prostaglandins - derived from arachidonic acid 
Proteins and peptides 
Gases
86
Q

How does endocrine signalling work?

A

Signal produced by cells in one part of body and travels in blood to target cells elsewhere

87
Q

How does autocrine signalling work?

A

Signal acts on same cell that produces it

88
Q

How does paracrine signalling work?

A

Signal produced by cell acts on other cells that are very close

89
Q

How does contact dependant signalling work?

A

Signal integral part of 1 cell and interacts directly with another cell

90
Q

How does neuronal signalling work?

A

Electrical signal transmitted down cell + message passed to another via synapse

91
Q

If hormone is hydrophilic, where is the receptor located?

A

Cell surface

92
Q

If the hormone is hydrophobic, where is the receptor located?

A

Intracellular

93
Q

What three domains does a steroid hormone contain?

A

Hormone binding domain
DNA binding domain
Domain for interacting with other transcription factors

94
Q

How many transmembrane regions does GPCR have?

A

7

95
Q

What does activation of the adenylyl cyclase produce?

A

Adenosine 3’:5’ cyclic monophosphate (cAMP)

96
Q

What does activation of the phospholipase C produce?

A

Inositol 1,4,5 - triphosphate (IP3)
1,2-diacylglycerol (DAG)
Metabolises components of plasma membrane to become secondary messengers

97
Q

Which part of the G protein complex dissociates when GTP binds?

A

Alpha subunit

98
Q

How does the toxin produced by Vibrio cholerae cause the symptoms of cholera?

A

Enters epithelial cells + causes irreversible modification of Gs protein
Increased ion + H2O transport across gut wall into lumen

99
Q

When RBC in liver are broken down in spleen and liver, what is haem broken to?

A

Bilirubin

100
Q

What type of covalent bond is important for the subunit stability of proteins?

A

Sulfhydryl bridges between cysteine residues

101
Q

A globular protein X found in blood can act as a buffer.
If the pKa of the protein is increased because of conformational changes in that protein how will the buffering/ hydrogen ion binding properties be affected?

A

Protein will bind more H+

102
Q

At physiological pH which two amino acid residues are completely negatively charged?

a) Glu and Asp
b) Gln and Asp
c) Glu and Asn
d) Gln and Asn
e) Glx and Asp

A

Glu and Asp

103
Q

How are secretory vesicles targeted to correct location in a cell?

A

V-snare protein on vesicle binds complementary t-snare protein in membrane

104
Q

How is the lysosome created in a cell?

A

By vesicle targeting of Golgi body

105
Q

Proteins are targeted to which organelle by the protein sequence Pro-Lys-Arg-Lys-Arg-Lys-Val?

A

Nucleus

106
Q

The Na-Glc transporter is involved in what kind of transport?

a) Active transport
b) Secondary active transport
c) Simple passive transport
d) Gated ion transport
e) Facilitated diffusion

A

Secondary active transport

107
Q

What are anchored proteins?

A

Proteins that are covalently linked to a fatty acid chain or to surface glycolipid

108
Q

What are lipid rafts?

A

Ordered membrane microdomains linked to cell signalling that have high levels of cholesterol

109
Q

What happens when EGF binds its specific receptor?

A

EGF receptor dimerizes and is auto-phosphorylated

110
Q

What is the composition of microtubules?

A

Polymer of alpha-tubulin + beta tubulin heterodimers

111
Q

What is the definition of the peptide bond?

A

Covalent linkage between amino acid residues that prevents rotation around C-N bond that results in R-groups being in trans arrangements

112
Q

What is the sequence of molecular events that occurs when an agonist binds to its specific G-protein coupled receptor?

A

Conformation change in cytoplasmic domain of receptor
GTP binds to the G protein
G-alpha subunit dissociates
G-alpha subunit activates adenylate cyclase
cAMP created
cAMP activates Protein Kinase A

113
Q

What subunits is PKA (protein kinase A) made up of?

A

Tetrameric enzyme

2 regulatory, 2 catalytic subunits

114
Q

What part of PKA does cAMP bind to?

A

Regulatory subunits

Catalytic monomers are now activated

115
Q

What is CREB and what enzyme phosphorylates it?

A

cAMP Response Element Binding protein

PKA

116
Q

What enzyme does the Gq subunit activate and what reaction does is subsequently catalyse?

A

Phospholipase C

Cleaves inositol phosphate in membrane (IP3 + DAG)

117
Q

Which GLUT receptor is associated with levels of glc within cell being same as outside cells?

A

GLUT2

118
Q

What are some examples of supersecondary structures?

A

Beta barrel
Beta sheet rolled
Beta sandwich
Rossmann fold

119
Q

Which AA are…..

a) Positive?
b) Negative?
c) Uncharged polar?
d) Non polar?

A

a) E,D
b) H, K, R
c) S, N, Q, Y, T
d) A, G, V, L, I, P, F, M, C, W

120
Q

What are 3 examples of non-coded AA?

A

Hydroxyproline - hydroxylation of proline, prt collagen
Selenocysteine - Contains Se, not S, encoded by subset of stop codons
Homocysteine - extra methyl group compared to C

121
Q

Describe process of kinase cascade

A 
EGF binds, autophosphorylates tyrosine in RTK​ (receptor tyrosine kinase)
GRB2 and Sos bind to receptor​
GDP-Ras to GTP-Ras​
Triggers kinase cascade​
MapKKK to MAPKK to MAPK​
MAPK activates transcription factor
122
Q

Which is the only amino acid whose side chain contributes to buffering at physiological pH?

A

His

123
Q

Amino acid side chains which are able to act as donors in forming hydrogen bonds include those which have what property?

A

Uncharged + polar

124
Q

During what stage of the cell cycle do growth factors stimulate a cell to continue dividing?

A

G1

125
Q

Kinase enzymes, such as glycogen synthase kinase, belong to which class of enzymes?

A

Transferases

126
Q

In which type of reaction is FAD used as a cofactor?

A

Oxidation

127
Q

Which cellular enzyme catalyses the production of the second messenger cyclic AMP (cAMP)?

A

Adenylate cyclase

FBS1 (5 decks)

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