cell biology 4 Flashcards
what is the function of peroxisomes
- perform oxidation reactions using oxygen and peroxide
what is the function of catalase
- converts peroxide to water and oxygen
- peroxidation of substrate
what is urate oxidases function
- uses oxygen
- breaks down toxic uric acid
- produces peroxide and allantoin
- allantoin cleared by kidneys
what are plasmalogens
- class of phospholipid
- most abundant in myelin 80-90%
- originate in the peroxisome
what is the function of plasmalogens
antioxidant - protects the cell
- affect fluidity, thickness and lateral pressure
what diseases are linked to peroxisome dysfunction
- alzheimers
- parkinsons
how are peroxisomes formed from the ER
- various membrane peroxisomal targeting sequences
- PEX13/16 aid membrane protein insertion
- vesicles transport to form peroxisomes
how are peroxisomes made in the cytosol
- targeting signals - PTS1(c-terminal and recognised by PEX5) and PTS2 (n-terminal)
- imported proteins can be folded or in complexes
- import requires PEX1/6 and ATPase with ATP
- PEX5 is ubiquitlyation recycles PEX5 in cytosol
what causes zellwegar spectrum disorder
- autosomal recessive
- defects in peroxisomal targeting —> peroxisome deficiency
what are the symptoms and treatment of zellwegar spectrum disorder
- Varies in severity (Mutation/gene)
- Abnormalities in brain, liver, and kidneys
- High mortality
- Cranial abnormalities, vision problems, hearing loss
Treatment
- None, treat symptoms.
what are the functions of primary lysosomes
- break down intra- and extra- cellular debris
- use acid hydrolases
- maintain internal pH 4.5-5
- found in all eukaryotic cells
- diverse in shape and size
what is a secondary lysosome
- primary lysosome fused with another cellular compartment
what is an endolysosome
primary lysosome fused with late endosome
what is the early endosome
fused endocytic vesicles, tubular projections, recycle material to surface
what are recycling endosomes
recycle material to surface, can store proteins unit they are needed
what are multivesicular bodies
formed by early endosome, self investigation, requires ESCRT protein complex
what is the late endosome
no tubular projections, fuse with lysosomes/ MVP
what are the functions of the nucleus
- genetic storage
- DNA replication
- transcription
- compartmentalisation/ genetic regulation
- RNA processing
- ribosome assembly
what is heterochromatin
dense, inactive DNA
what is the function of the nucleolus
- rRNA and tRNA production
- RNA modification/ processing
- ribosome subunit assembly
what are the characteristics of aqueous passages in nuclear pores
- small molecules can diffuse passively
- 1000 macromolecules per second
- bidirectional flow
- > 60000 daltons cannot enter passively
- maintains different protein compositions
- specific transport mechanism used
how many nuclear pores per nuclei
3000
what does nuclear pore complex consist of
100s of proteins - 30 different types of nucleoporins
what do disordered pore regions do in NPCs
- restrict movement of large molecules
- phenylalanine-glycine (FG) - repeats of disordered pore regions
what are nuclear localisation signs and what do they do
1-2 short surface sequences
rich in lysine/arginine
whole complexes can be transported
what are nuclear import receptors and what do they do
- soluble cytosolic proteins
- recognise NLSs
- family of proteins - different type —> different cargo/signal
- work together with adaptor proteins
- binds to phenylalanine-glycine repeats in the disordered region of channel nucleoporins
where is the nuclear lamin
- nucleoplasm side of the inner nuclear membrane
- made from intermediate filament proteins
- anchored to pore complexes and transmembrane proteins
what is the function of nuclear lamin
- provide shape and stability
- interacts with chromatin at the membrane
what happens to nuclear lamin during mitosis
- NPCs and nuclear lamina disassemble to nuclear envelope fragments
- caused by direct phosphorylation of nucleoporins and lamins by the cyclin-dependent protein kinase
- pore complex reassemble
what happens to ran proteins during mitosis
- Ran-GEF remains bound to chromatin
- ran proteins close to chromatin mainly GTP bound
