Cytology 3-4 mitochrondria and lecture 3(cytoskeleton) and 4(nucleus) Flashcards
Which stain used to detect mitochondria and which colour is positive?
Mitotracker - pink
Importance of granules in mitochrondria
Maintain low levels of Calcium and Mg ions.
Store these ions
What makes mitochondria semi-independent? (5)
Replicate by fission or fusion with other mitochondria - form larger mitochrondria MtRNA, DNA - protein synthesis Mito-ribosomes Mt DNA - circular similar to plasmids RNA polymerase
Composition of outer mitochondrial membrane? (4)
50% lipids - main phosphotidylcholine
Porins - channel proteins
Similar to ER membrane
Enzymes - (lipid synthesis, fatty acid metabolism)
Inner membrane composition?
20% lipids
Cristae or tubular (in cells specialised for steroid hormone synthesis)
3 transport proteins
Enzymes for ETC and ATP synthase
Where are tubular inner membrane mito found?
Cells syn of steroid hormones. Eg adrenal glands, gonads.
What is an inclusion?
Not metabolically active cytoplasmic component.
Give 5 examples of inclusions
Glycogen - hydrolysed to glucose.
Lipid droplets of fat - triglycerides - energy store, insulation, protection.
Cholesterol - component in lipid and steroid hormone synthesis.
Lipofuscins - dead residual body from lysosomal digestion. Increase with age. Common in stationary cells. E.g. Cardiac, skeletal, neurons.
Plectin - adhesion of 3 structural proteins. Micro, intermediate filaments and microtubules. Found at cell to cell junctions.
Actin and microtubules tread-milling req.
Actin - atp, mg2+, k+
Microtubules - gtp, mg2+
How are mito proteins formed in the cytosol?
Specific Terminus C AA sequence.
Followed by heat shock protein 70.
Translocation into mitochondria via TOM - ITM
Heat shock protein 70 cleaves AA positive terminus C sequence,
At what inclination does actin bind to myosin?
45 degrees
Function of actin binding protein?
Accelerate/decelerate polymerisation of actin filaments.
What type of myosin do non muscle cells contain?
Myosin I
Nucleus quick points (4)
DNA, Double bilayer membrane, nucleolus (protein synthesis), continuous with ER
Nucleus irregular in….
Leukocytes, plasma cells, spermatozoa
Observing nucleus…..(4)
Display different shapes,
Not present in all cells eg rbs, platelets
Not present during whole cell cycle (nucleolus)
Multiple nucleus present eg syncytia, plasmodia, dome cells
Ratio of nucleus to cytosol
Vn / Vcytoplasm - Vn
= k
If k not constant - pathology
Nucleolus
No membrane, basophilic, granular and fibrillar layer. Breakdown during pro-metaphase. rRNA transcription Synthesis of ribosomal sub units. Surrounded by nuclear chromatin
Inner nuclear membrane?
Unique proteins - nuclear lamina - filaments -> lamin proteins A B C
2 types of chromatin in NUCLEUS
Euchromatin - dark, active
Heterochromatin - compacted, not active, electron dense
Nuclear lamina size
25nm
Cell cycle, lamin phosphorylation
Prophase, lamin phosphorylation, breakdown NE
Telophase, lamin dephosphorylation, reform NE
Nuclear lamina (4)
Intermediate filaments beneath NE,
Provides shape and stability, link between DNA + envelop.
Regulates chromatin compartment - therefore gene expresson reg.
Therefore mutation of proteins effects gene expression
3 laminopathy
Muscular laminopathy - muscle weaken, die - skeletal muscle, heart, conduction of heart
Lipodystrophies - loss of fat from facial area. Decrease in leptin ( hormone which regulates satiety - controls lipid met)
Progeria laminopathy (premature ageing) - patients die within 20 years of birth. Due to abnormal lamin A - accumulation into nucleus therefore effect lamina formation - therefore effect gene expression
What is a npc?
Nuclear pore comples
Function of NPC
Channel which Regulates movement of proteins/rna in/out of nucleus
Nuclear pre example no.
Somatic - 10-20/um^2
Ooctye 40-50/um^2
Active cell - greater no. of pores
6 structural features of a NPC
Luminal anchor, Luminal ring, Basket, Ring, Filament, Scaffold
Trafficking thru nuclear pores?
Importins - specific proteins - contain Nuclear localisation sequence(NLS)
Exportination - less common - nuclear exp. sequence (NES)
Active transport of proteins into nucleus and give example.
Receptor for import.
Bind to nucleus.
Moved thru pore via cytosol fibrils.
Passage requires : GTP
EXAMPLE: ribosome subunits. Proteins syn in cytoplasm. Contain NLS. Into nucleus-nucleolus. Synthesis of ribosomal subunits. Back into cytoplasm
Nucleoplasm and nucleocytoskeleton
80-90% proteins, 10% Nucleic acids, 1% lipids
Nucleocytoskeleton : fibrous lamina, fibrillary network
3 structural areas of nucleolus
Fibrillar centre - light stain - 5 chromosome - contain rRNA gene
Dark straining region
Pars fibrillosa - processing + precursor of rRNA
Pars granulosa - assembling of ribosome subunits - completed jn cytoplasm
Time taken for a eukaryotic cell to divide
2hr-3days
Interphase 3 subphases
G1 protein syn, organelle replication
S dna replication
G2 atp syn, cytoplasmic element doubling, form mitotic spindle
Which staining to see mitosis and nucleus in detail?
Feulgen staining - fluorescent strain - red:chromosomes. Green : filaments.
3 types of MT In mitotic spindle
Free - located at radial MTOC
Kinetochore - shorten, contract - depolymerisation
Polar - lengthen at positive end and slide
Dephosphorylation of lamins causes?
Telephase - NE To reform Then cytokenesis ( division of cytoplasm ) - contraction of contractile ring (containing actin and myosin)
Time taken for MITOSIS
G1 8++ hr
S - 7-10hr
G2 - 2-5hr
Ipmat - 2 hour
What is the G0 phase
Resting phase. No replication.
Eg neurons and cardiac muscle. Permanently in resting phase
Cell renewal (3)
Static - resting phase - eg neurons, cardiac muscle.
Stable - quiescent - eg remove portion of hepatocytes stimulated to replicate.
Continuos - renewing - epidermis
Cell no. Maintainence
Proliferation, differentiation, apopsis (programmed cell death)
Cell differentiation - 3 types of genes
House keeper - constitutive genes
Conditional ( on/off )
Specialised ( expressed in certain types of tissue, function and time specific)
Apoptosis definition
Programmed cell death. Condensed chromatin therefore inactive therefore no rRNA syn therefore no ribosomes therefore no protein synthesis.
Morphological changes in apoptosis
Cell shrinkage - modification of PM ( phosphotidylserine translocated from PM to EC face). Mitochrondria destruction -> cytochrome C released - activates enzymes (Caspases) - digest cell substrates -nuclear changes (dna fragmentation).
Necrosis
Cell death after injury
1 cell swell
2 cell lysis
3 tissue inflammation ( apoptosis no inflammation )
CASPASES
Activate Dnase -> dna fragmentation
Gel electrophoresis of apoptotic cells
Normal cell - high molecular weight
Apoptotic cells - dna ladder formed
Necrotic cells - low weight
5 types of actin binding protein
Actin binding protein - fibrin, fascin (eg microvilli) cross link actin filaments into parallel strands
Actin filament severing - cut into short fragments (eg gelsolin - high ca2+ conc - severing)
Acting capping - tropomodulin - prevent polymerisation
Actin cross linking - cross link actin filaments ( spectrin, actin, protein 4.1, 4.3
Actin motor proteins - hydrolysis of atp - recock myosin head
