DNA Flashcards
DNA associates with proteins into
chromatin
heterochromatin
remains packed after mitosis and is not transcriptionally active. 10% of the DNA
Euchromatin
transcriptionally active
heterochromatin is
black
euchromatin is
white
DNA is … wide
2nm and negatively charged
DNA associates with
8 coe histones which they wrap around twice (histones ar eposiitvely charged).
nucleosomes re
folded even tighter and produce a 30nm fibre.
interaction between DNA and ….. results in more package
histone 1–> produces a 300nm fibre.
DNA is further packed around
scaffold that contains specialised proteins
RNA pol 1
ribosomal RNA
RNA polymerase 2
mRNA
RNA pol 3
transfer RNA
RNA 4
plants, siRNA, required for heterochromatin formation
prokaryotes
just 1 RNA polymerase
the ER
found everywhere in the cell and is a membranous synthesis and transport organelle that is an extension of the nuclear envelope
tubules of the ER
are motile
two different types of ER
smooth and rough
rough ER
has ribosomes on the outside and is responsible for processing of secretory protein
smooth ER
calcium store for cell signalling, lipid synthesis, detoxification of drugs/poisons, metabolism of carbohydrates
cotranslational translocation into the ER
1) Ribosome assembles and binds mRNA
2) If polypeptide contains a signal sequence it is targeted to the ER membrane
3) The signal peptide is cleaved off and the protein is translated into the ER lumen where it is folded and further processed
4) Cytosolic proteins can contain signal sequences that target them to other organelles
ER makes up… of the cells membrane
50%
signal sequence for ER proteins usually consists of
5-10 hydrophobic amino acids at the N terminus
where d most proteins get further modified
in the ER e.g. linkage to a sugar residue (oligosaccharide)
what sort of plasma membrane receptors are there for insulin
type I, II and IV
Golgi apparatus
disk shaped stack of membranes, golgi receive vesicles from the ER and process the content and from here the processed material can be sent to the plasma membranes or lysoosmse
Cis (golgi)
vesicles from ER
trans (golgi)
processed material to plasma membrane and lysosome
how is material passed through the network (golgi)
via maturation of the golgi cisterns, finally the material will form into secretory vesicles
who discovered golgi
camillo golgi
how do you get a 3D view of the golgi
serial sections through the golgi are taken
when are sugar residues on proteins e.g. glycoproteins NOT added
translation process
role of oligosaccharides
- protects against pathogens
- cell-cell recognition
- marks progression of the protein
- helps folding and interaction with other proteins
where are oligosaccharide chains processed and proteoglycans assembled
in Golgi
–> most proteins that arrive from the ER eat cis Golgi contain a N-linked oligosaccharide (glycoprotein)
how many ways can oligosaccharides be linked to proteins
2 ways: N-linked
O-linked
50% of all eukaryotic proteins are
glycosylated
N-glycosilation already in
prokaryotes
oligosaccharides can be linked to
asparagine and threonine
at the cis network of the golgi
sorting: phosphorylation of oligosaccharides on lysosomal proteins
at cis cisterna
removal of Man
at medial cisterna
-removal of Man and addition of GlcNAc
trans cisterna
-addition of Gal and addition of NANA
trans Golgi network
sorting: sulfation of tyrosine sand carbohydrates
three products from the golgi
lysosome, plasma membrane, secretory vesicle
N-linked
inked by nitrogen
O-linked
lined by oxygen
