lectures 5-6 Flashcards
properties of nuclear envelope
double membraned
interacts with endoplasmic reticulum
contains nuclear pores
euchromatin
transcriptionally active
mRNA made by RNA polymerase II
‘lighter’ areas
heterochromatin
remains packed after mitosis - more condensed
transcriptionally inactive - no mRNA made
nuclear lamina
- net of fibres
- prevent clustering of nuclear pores
- disassembles/falls apart with the nuclear envelope during mitosis by phosphorylation of the lamins by kinases (lamins form intermediate filaments)
- only found in animal cells
- provide mechanical support and stability
nuclear pores
- 8-fold symmetry – 8-subunit protein complex
- highly organised and equally distributed
- control nuclear transport – act as a gate and restrict transport of large proteins
- 30 different nucleoporins in a pore form the selective gates
nucleolus
- assembles ribosomal subunits from proteins and exports them to cytoplasm
- fibrillar components – rRNA transcription
- granular components – ribosome assembly site
what are the compartments of the endomembrane system
Nucleus - Endoplasmic Reticulum - Golgi Apparatus - Lysosome/Vacuole - Endosomal compartment - Transport vesicles - Peroxisomes
what are the 3 vesicular trafficking pathways
- secretory
- endocytic
- retrieval-recycling
what ‘cargo’ do transport vesicles carry
integral proteins
phospholipids
cholesterol
how are transport vesicles moved
molecular motors
endoplasmic reticulum
- consists of membranous sacs and branched tubules
- Proteins can diffuse and migrate within the motile tubules
- extension of nuclear envelope
differences between SER and RER
smooth: - calcium storage for cell signalling - lipid synthesis - detoxification of drugs/poisons - metabolism of carbohydrates rough: - processing of secretory proteins
golgi apparatus
Disc-shaped stack of membranes
Each golgi receives information at the Cis site from ER and processes it in golgi network
Sends information to plasma membrane or lysosomes from Trans site by vesicles
Some vesicles are sent back to ER by maturation of the golgi cisterna – retrieval-recycling pathway
Double membranes fold around forming compartments
involved in membrane trafficking
functions of oligosaccharide
- provide protection against pathogens (e.g. mucus coat on epithelia)
- serves in cell-cell recognition and signalling
- marks progression of the protein
- helps folding and interaction with other proteins
where are oligosaccharide chains processed
golgi cisterna