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Cell Biology > Nucleus, Signal, Death, Division > Flashcards

Nucleus, Signal, Death, Division Flashcards

(53 cards)

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1
Q

Chromatin

A

DNA is found wrapped around Histones
Euchromatin is lighter, allows expression
Heterochromatin- present in the structural centromere, nuclear lamina and telomeres.
Facultative heterochromatin can switch between states

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2
Q

RNA splicing islands

A

Nucleolus has chromatin organised into islands of DNA and RNA

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3
Q

Chromosome territory

A

The DNA from each chromosome occupies a distinct territory.

Short parts can be de condensed, transported to transcription islands and recondensed

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4
Q

Nucleolus

A

Site of ribosome production, which are essential for translation

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5
Q

Speckles

A

Sites of accumulation of splicing factors, but not splicing itself.
Used as storage.

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6
Q

Cajal body

A

Formation of essential splicing factors
Contains:
Coilin
SMN (survival of motor neurons protein)
Role in biogenesis or snRNP splicing factors
SMN mutations -> spinal muscular dystrophy

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7
Q

Ribosome creation

A

Genes from different chromosomes are brought together and transcribed creating large amount of RNA

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8
Q

Nucleoplasmic transport

A

Nuclear proteins bind to nuclear import receptors allowing them to travel through the pore
Transcription factors are created and then imported into the nucleus for gene regulation
Bidirectional, energy requiring and regulated

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9
Q

Things travelling into the nucleus

A 
Matrix proteins
Lamins
Chromatin components
Enzymes
Transcription factors
Conditionally cytoplasmic proteins
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10
Q

Things travelling out of the nucleus

A

Mature mRNA
tRNA
rRNA as subunits
SRPs

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11
Q

Inside of the nuclear lamina

A

Alpha helices wrap around to form a coiled coil
Lamina CNS be phosphorylated by normally associated head to head
Tetramer then form criss cross patterns

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12
Q

B type lamins

A

Near the nuclear membrane and bind to integral proteins inside that membrane
Are then isoprenylated (lamin B receptor)

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13
Q

A/C lamins

A

Inside next to the nucleoplasm, phospharylated.
Functional organisation of the nucleus
Phosphorylation triggers disassembly of the lamina and nuclear envelope
-> vesicles
Dephosphorylation reforms the nuclear (mitosis etc.)

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14
Q

Functions and structure of the nucleus

A

DNA transcription
RNA modification
Ribosome assembly
DNA replication and repair

Kept centrosomes in the cell by micro tubules
Surrounded by 2 bilayers with a lumen that is continuous with the ER

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15
Q

Cadherins

A

E cadherin - epithelial (ectoderm)
N cadherin- neural
Calcium allows stretching out and interaction
Most homophilically some heterophilically

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16
Q

NCAM and ICAM

A

Immunoglobulins

Mediate Ca+ independent cell- cell adhesion

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17
Q

Selectins

A

Expressed on surface on WBCs
Helps slow down
Uses integrin to pass through endothelium

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18
Q

Adherens junctions

A

Actin filaments bind to alpha-catenin
Catenins link to cadherins
When myosin pulls on actin, forms dip in membrane
Can be used for endocytosis

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19
Q

Tight junctions

A

Seal between cells
Barrier between plasma domains
NA+ glucose transporters allow glucose into cell
At the basal lamin da straight diffusion is allowed
Separate transporter proteins into groups
Claudin and occlusion sew cells together, 4 pass membrane

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20
Q

Desmosomes

A

Give epithelia mechanical strength
Connects intermediate filaments in neighbouring cells
Intermediate filament -> desmoplakin -> plakoglobin + plakophilin -> desmoglein + desmocollin

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21
Q

Hemidesmosomes

A

Bind the basal lamina (bottom of cell)

Anchors intermediate filaments to extra cellular matrix

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22
Q

Gap junctions

Study These Flashcards
A

Couple cells electrically and metabolically
Connexins -> 2 stacked hexamers (connexons)
Homotypic or heterotypic

23
Q

Extra cellular matrix

Study These Flashcards
A

Proteoglycans- GAG chains covalently linked to core protein
Core protein linked by serine -> tetrasaccharide -> GAG
Fibrous protein (collagen)
Glycoproteins
Hyalauron with sulphate glycoproteins fills large volumes. Binds cations and water and regulated movement
Can affect stability and activity of proteins

24
Q

Organisation of collagen

Study These Flashcards
A

Cells organise collagen by exerting tension
Fills environment
Type 9 can modify type 2

25
Elastin
Gives tissues elasticity | Can form cross links when stretched
26
Glycoproteins in organisation
Fibronectin Help organise matrix Collagen, integrin and heparin binding domains
27
The basal lamina
Specialised form of ECM Made of a,b,y lamin twisted together Also nidogen, perlecan, collagen 4 and integrin
28
Integrins
Transmembrane heterodimers Link EM to cytoskeleton Defects -> skin blistering, muscular dystrophy Active and inactive conformations
29
Platelets stuck
Thrombin -> G protein -> actin binds to talin Talin is activated by stretching, exposes vincluin binding sites Actin recruited and change in cytoskeleton
30
External signalling compounds
Nicotine, Valium, morphine Shape, growth, fusion, division Signalling allows survival, cytokines, differentiation or apoptosis
31
Types of external signals
Receptor or permeating Transient (protein) or prolonged (protein synthesis) Receptor -> kinase amplification -> effector protein -> response
32
3 major classes of cell signalling mechanisms
Ion channel coupled- ion flow across membranes G-protein coupled- receptor activated G protein Enzyme coupled receptors- recruitment of signal molecules to receptor
33
7-TM GPCRs
Binding allows binding to G protein GDP dissociates and GTP binds to alpha subunit BY unit also activated, seperation from a. Beta has Trp and Asp Receptor regulated by GEF and GAP Adenylate cyclase -> cAMP. 4 cAMP -> PKA PKA activates phosphorylase kinase -> glycogen phosphorylase -> glycogen breakdown
34
Responses mediated by cAMP
Adrenaline- heart rate and force Adrenaline- glycogen breakdown in skeletal ACTH- cortisol secretion from adrenal gland ACH binds to endothelial -> NOS -> Arg -> NO NO -> guanylyl cyclase -> cGMP -> releases smooth muscle
35
Phospholipase C
Activated by G proteins Removes fatty acid tail from PI(4,5)p2 -> diacyglycerol tail Diacyglycerol -> protein kinase C
36
Calmodulin
Resembles ThC Can activate peptide portion of target protein E..g cam-kinase
37
Receptor tyrosine kinases
Cysteine rich domain (top) linked across membrane to tyrosine kinase When signal molecule binds -> activates tyrosine kinase Forms dimers Autophosphorylation -> active Recruitment of messengers Ras GEF -> Ras Starts MAPKKK -> MAPKK -> MAPK-> gene expression
38
Cell survival signalling
Lack of signal -> apoptosis
39
Cell contact signalling
Ephrin receptor -> actin filament modification | Directs cell movement
40
Distinct changes in cells in apoptosis
Membrane blebbing Nuclear morphology Chromatin changes Phagocytosis by adjacent cells
41
Apoptosis during development
Tadpole -> frog metamorphosis Digit formation- apoptosis in we bind of chicken feet but not duck Nervous system- destruction of unused neurons
42
Ced genes
Control cell death. Many involved in engulfment. Ced3 and ced4 needed for apoptosis, mutation causes over growth Ced9 is antagonist to 3 and 4 (opposite) Over expression of 9 -> excess cells Loss of ced9 -> massive cell death
43
Mammalian equivalent of of Ced genes
Ced9 -> bcl-2 Ced4 -> APAF-1 Ced-3 -> ICE
44
Caspases (Ced3)
Cleaves target proteins terminal -> aspartic acid Acts as 'inhibitor capsase' -> proteolysis -> executioner caspases activated Signal amplification
45
Membrane blebbing
Proteolysis causes cleavage of membrane cytoskeleton (Spectrin) Activation of nucleases that disassemble chromatin -> nucleoside ladder
46
UV damage to DNA
Damage activates p53 -> inhibits cell cycle -> apoptosis Common in cancer Escape apoptosis
47
Anti apoptotic Blc2 protein
Bcl2, bcIxL Bind and inhibit effector proteins bax and bak (Homologous of ced9)
48
Pro apoptotic effector blc2 and BH3- only
Bax and bak Stimulus activates BH3-only protein -> bax and bak form channel Activation -> permeability -> apoptosis Intermembrane proteins released (cyt C) BH3-only - bad, bim, bid, puma, Noxa
49
Release of Cyt C during apoptosis
Activation of Apaf1 | Assembly of apoptosomes -> recruit and activate caspases
50
Signals that activate apoptosis
Lack of survival signal Killing factors- TNF, p53 activation
51
Neuron death
Survival factor- NGF and BDNF Fas ligand + TNF -> receptor -> activate effector caspases Neurone grenadine diseases?
52
Cell surface death receptors
Fas ligand -> receptors Assembles DISC Activation and cleavage of caspase 8 Apoptosis
53
Signals which inhibit apoptosis
Increased blc2 Inactivation of BH3-only Inactivation if anti-IAPs

Cell Biology (4 decks)

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