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FBS1 > Cell Biology & Signalling > Flashcards

Cell Biology & Signalling Flashcards

(45 cards)

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1
Q

What is tyrosine the precursor of?

A

Epinephrine, dopamine and melanin

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2
Q

What is tryptophan the precursor of?

A

Serotonin

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3
Q

What are the essential amino acids?

A 
Phenylalanine, F
Valine, V
Tryptophan, W
Threonine, T
Isoleucine, I
(Methionine, M)
Histidine, H
(Arginine, R)
Leucine, L
Lysine, K
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4
Q

Anchored membrane proteins examples

A 
Alkaline phosphatase (glycolipid anchored)
RAS (fatty acyl anchored)
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5
Q

Peripheral proteins example

A

Spectrin (interacts with ankyrin)

Phospholipase A2

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6
Q

What are the different phospholipases?

A 
PLA1,2= FA from phospholipid
PLC= phosphate group from glycerol
PLD= phosphate group from polar head group
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7
Q

What is the effect of pH on the affinity of Hb for oxygen?

A

Increase in pH —> increase in affinity

Decrease in pH —> decrease in affinity

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8
Q

What is the effect of BPG on Hb affinity to O2?

A

Increased BPG —> decreased affinity

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9
Q

Where on hemoglobin does heme bind?

A

Histidine residues from helixes E7 (distal) and F8 (proximal)

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10
Q

What mutation causes sickle cell anemia?

A

Glu6 (acidic) to Val (nonpolar) in beta-chains

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11
Q

What are porphyria and thalassemia?

A

Porphyria: inherited defect in synthesis of heme group
Thalassemia: reduced synthesis of alpha or beta chains

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12
Q

How does protein targeting to the ER happen?

A

signal sequence at N-terminus, recognised by signal recognition particle (SRP), SRP receptor in ER membrane, translocation channel, signal peptidase cleaves signal sequence

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13
Q

What is the tag for proteins that form lysosomes?

A

mannose-6-phosphate

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14
Q

How does protein targeting to mitochondria happen?

A

translated but unfolded protein, chaperones take it to the mitochondria, signal sequence recognised by receptor –> translocation across outer and inner m, cleavage of signal sequence

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15
Q

How does protein targeting to the nucleus happen?

A

Translation and folding in cytoplasm, nuclear localisation signal (NLS; basic) binds to importin and transported through the nuclear pore, requires G-protein Ran and GTP,

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16
Q

What are glycosyltransferases?

A

Golgi enzymes that add sugars to proteins

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17
Q

How many actin monomers are needed for a full turn and what is the diameter of the filament?

A

13; 7 nm

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18
Q

What are the major functions of actin?

A

Mechanical support, cell shape changes and maintenance, cell motility

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19
Q

What is the diameter of intermediate filaments and what are some examples?

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A

10 nm; keratin, vimentin, glial fibrillary acidic protein, neurofilamin

20
Q

What is plectin?

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A

protein links IFs to actin and microtubules

21
Q

How many columns of tubulin polymer are arranged to form the microtubule and what is its diameter?

22
Q

What is required for the assembly of actin filaments and microtubules?

Study These Flashcards
A

Actin filaments: ATP

Microtubules: GTP

23
Q

What is responsible for shape of microvilli and stereocilia?

Study These Flashcards
A

Actin filaments

24
Q

What is responsible for the organisation the ER of a cell, nucleus support and synaptic vesicle positioning?

Study These Flashcards
A

ER: microtubules
Nucleus: intermediate filaments
Synaptic vesicles: actin filaments

25
What molecules are responsible for focal adhesion?
Integrins
26
What are examples of microtubule based movements?
Cilia and flagellae | 9+2 structure + dynein
27
What motor protein is responsible for movement of lamellipodia?
Myosin II (requires ATP, not processive)
28
Which motor proteins are responsible for movement of organelles and intracellular contents?
Kinesin (processive motor protein, requires ATP) and dynein (both have heavy and light chain) on microtubules
29
What are colchicine, vinblastine and taxol?
Anti-cancer therapeutics; Colchicine and vinblastine: destabilise microtubules Taxol: stabilises microtubules
30
What is Tau and what happens to it in Alzheimer's disease?
Microtubule associated protein | In AD it is hyperphosphorylated and thus cannot bind to MTs
31
How does the Listeria bacteria interfere with the cytoskeleton of the cell?
F-actin is polymerised at the back of the bacterium providing mobility
32
What is sphingomyelin composed of?
Ceramide (sphingosine + fatty acyl chain) + phosphate group + choline
33
What is the partition coefficient?
Equilibrium constant for the partitioning of a molecule between oil and water (the higher the more lipid soluble)
34
What are the characteristics of GLUT1, 2, 3, 4, 5?
GLUT1: low Km, many tissues, highly expressed in erythrocytes and blood-brain barrier GLUT2: high Km and large Jmax (high capacity), hepatocytes and pancreatic beta cells. GLUT3: low Km, high expression in neurons GLUT4: muscles and adipocytes, regulated by insulin. GLUT5: fructose transporter
35
How does ouabain work?
blocks Na+/K+ ATPase --> increase in intracellular sodium --> Na+/Ca2+ antiporter is inhibited --> increase in intracellular Ca2+ --> cardiac muscle contraction
36
What is SGLUT1 and where is it located?
Na+/glucose transporter; intestinal epithelial cells and proximal tubules of the kidney for reabsorption of glucose
37
What is the method of action of cholera?
Overacting Gsalpha --> increased cAMP levels --> increased transport of Cl- out of the cell through CFTR --> diffusion of Na+ and water out of the cell --> glucose replacement therapy drives Na+ back through SGLUT1
38
What type of receptor is the beta adrenergic receptor?
G-protein coupled receptor
39
How are G-proteins activated?
GTP binds to alpha subunit --> dissociates from beta and gamma subunits
40
How is PKA activated?
cAMP binds to regulatory subunits (2) --> tetramer dissociates and catalytic monomers are now active
41
How is glycogen breakdown activated?
Glucagon activates GPCR --> cAMP --> PKA PKA: phosphorylates and thus activates phosphorylase kinase Phosphorylase kinase: phosphorylates and thus activates glycogen phosphorylase Glycogen phosphorylase: phosphorylates glycogen and thus produces glucose-1-phosphate
42
How is gene transcription activated through GPCR?
PKA phosphorylates CREB --> binds to specific target sequences in target genes and stimulates transcription
43
How is PLC activated and what does it do?
PLC is activated by GPCRs with Gq subunits (alpha1 adrenergic receptors) PLC cleaves inositol phospholipids into IP3 and DAG IP3: activates Ca2+ channels in ER DAG: together with Ca2+ activates PKC
44
What receptor does EGF bind to and what cascade does it initiate?
Receptor tyrosine kinase (RTK); Binding leads to autophosphorylation of tyrosine residues Adaptor proteins contain phosphotyrosine binding domains: SH2 and PTB Binding of adaptor proteins (Grb2, Sos) --> activation of Ras through GDP to GTP exchange
45
What is Ras?
Monomeric G-protein GTP-Ras triggers kinase cascade: MAPKKK --> MAPKK --> MAPK --> transcription factor

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