unit 6 - ER, GOLGI, LYSOSOMES

what is the main function of lysosomes

degradation of target compounds

lysosomes contain many enzymes for degradation give me 3 examples (there are more)

• proteases

• hydrolases

• lysozymes

the endoplasmic reticulum is divided into 2

• smooth ER

• rough ER

what is the functions of smooth ER and rough ER

smooth = lipid synthesis

rough = glycoprotein synthesis

smooth ER synthesises ….. and ……

lipids and hormones

apart from synthesis of lipids the SER is also involved in what process

detoxification

what is detoxification

removal of toxic compounds (mainly hydrophobic compounds) by the addition of OH (alcohol group)

are hydrophobic compounds soluble or insoluble

insoluble

in detoxification why do we add alcohol groups

to increase solubility

rough ER is the synthesis of what type of proteins

glycoproteins

the particle that is produced from the SER or RER is transferred where

Golgi Apparatus

what happens in the Golgi complex

• modify lipids and proteins

(final modification takes place here)

when the processes is done - so lipids and proteins have been modified in the Golgi complex - what is the destination of the lipids and proteins

the plasma membrane

endoplasmic reticulum

is composed of a set of membranes that form a network of saccules - called what

cisternae

endoplasmic reticulum

in the rough ER - it has …………….. 1 …. and the main function is

1. has ribosomes attached to the membrane

2. synthesis of glycoproteins

endoplasmic reticulum

in the smooth ER - it has…….1…… and the main function is…..2…

1. No ribosomes

2. synthesis of lipids and steroids

endoplasmic reticulum

RER and SER which has ribosomes

• RER = ribosomes

• SER = no ribosomes

Rough endoplasmic reticulum

membranes are thinner than the plasma membrane due to its composition of

_ proteins

_ lipids

70% proteins

30% lipids

1

membrane = 45%

RER= 30%

2

membrane = 45%

RER = 70%

3

membrane = 10%

RER = 0%

when we have the proportion 45,45,10 % what is the characteristic of the membrane

thick

when we have high levels of proteins what is the characteristic of the membrane

thinner

Rough endoplasmic reticulum

the RER is composed of 2 parts

• hyaloplasmic face (outer)

• Luminal face or lumen (inner)

Rough endoplasmic reticulum

Hyaloplamsic face is the membrane surface where what happens

where the ribosomes are inserted

Rough endoplasmic reticulum

the luminal face or lumen is always the

internal part of organelles

Rough endoplasmic reticulum

the luminal face or lumen is the internal part o organelles and - does or doesn’t contain ribosomes?

NO ribosomes

function of RER

1. produce glycoprotein

2. folding of proteins

3. transport to Golgi

what is a glycoprotein

protein + carbohydrate and this process is called glycosylation

folding of proteins into what

their tertiary structure

enzymes are involved in the folding of proteins into their tertiary structure - which enzymes

chaperons

chaperons use ATP meaning they are what

ATPase

proteins fold into their three dimensional shape and packaged into what

vesicles which go to Golgi

Rough endoplasmic reticulum

how many types of translation

2

Rough endoplasmic reticulum

translation 1 is called = 1

translation 2 is called = 3

1 = free-ribosome cycle

2= membrane-bound ribosome cycle

Rough endoplasmic reticulum

translation type 1 takes place where

the cytoplasm

Rough endoplasmic reticulum

translation type 1 (free ribosome cycle)

what happens

we us free ribosomes in the cytoplasm so make proteins

Rough endoplasmic reticulum

translation type 2 (membrane-bound ribosome cycle) takes place where

on the RER

Rough endoplasmic reticulum

translation type 2 - what molecule is produced

glycoproteins

Rough endoplasmic reticulum

translation type 2

the synthesis of glycoproteins depends on 2 processes

• translation and glycosylation

Rough endoplasmic reticulum

translation type 2

the synthesis of glycoproteins depends on translation and glycosylation these two processes happen at (important)

THE SAME TIME

Rough endoplasmic reticulum

why does translation take place in the RER and others in the cytoplasm

The ER signal sequence is NOT present in the cytoplasm,

however it is present in the RER so translation finishes there

READ

DONE

what is the ER signal sequence composed of

at least 8 hydrophobic amino acids

if my protein shows the ER signal sequence made up of hydrophobic amino acids what is the consequence

translation finishes in the RER

the hydrophobic amino acids are mainly composed of what in the side chain

carbon and hydrogen

the ER signalling sequence is recognised by what

SRP

what is SRP

signal recognition particle

the SRP is a what protein

is a ribonucleoprotein (protein-RNA-complex)

the SRP and ER signal sequence complex is dissociated via what

GTP hydrolysis

Rough endoplasmic reticulum

translocation from cytoplasm to ER

1. the ER signal sequence is located where

the amino terminal end of the polypeptide chain

Rough endoplasmic reticulum

translocation from cytoplasm to ER

2. recognition of ER signal sequence by Signal recognition particle results in

translation will be stopped

Rough endoplasmic reticulum

translocation from cytoplasm to ER

3. SRP binding-SRP receptor

directs what complex towards the ER

directs the SRP-growing polypeptide chain-ribosome complex towards the ER

Rough endoplasmic reticulum

translocation from cytoplasm to ER

4. SPR release - binding to the receptor frees the SRP from the complex and the ribosome binds to what

a channel of the membrane or translocon

Rough endoplasmic reticulum

translocation from cytoplasm to ER

5. the signal sequence is inserted into the translocon until what

protein synthesis ends

Rough endoplasmic reticulum

translocation from cytoplasm to ER

in ribosomes we have 2 subunits what are they

major and minor

Rough endoplasmic reticulum

translocation from cytoplasm to ER

what recognises the ER signal sequence X SRP complex

SRP receptor (in the RER membrane)

Rough endoplasmic reticulum

translocation from cytoplasm to ER

what happens when we have

the ER signal sequence X SRP complex X SRP receptor

GTP hydrolysis

Rough endoplasmic reticulum

translocation from cytoplasm to ER

what binds to translocon channel

ER Signal sequence

Rough endoplasmic reticulum

translocation from cytoplasm to ER

what happens in translocon chanel

translation

READ VERY IMPORTANT

DONE

READ

done

there are 2 types of proteins that are translated from the translocon channel

1. water soluble proteins

2. transmembrane proteins

1. water-soluble proteins

are ……….. translocated across the ER membrane

completely

1. water-soluble proteins

are completely translocated across the ER membrane and are ……………….. ( what happens after)

released into the ER lumen

1. water-soluble proteins

destination (2)

1. secretion at cell surface

2. lumen of an organelle of the endomembrane system

1. water-soluble proteins

where is the ER signal sequence located

in the amino end

1. water-soluble proteins

at the same time that the protein is being translated what is happening

glycosylation (addition of carbohydrates)

1. water-soluble proteins

the ER signal sequence is removed from the final protein by which enzymes

• proteases

• peptidases

1. water-soluble proteins

what do proteases do

break peptide bonds in proteins

1. water-soluble proteins

what do peptidases do

break peptide bonds in peptides

1. water-soluble proteins

the final protein is translated and released into the lumen - what happens here

it is folded into a tertiary structure to become a mature and active protein

1. water-soluble proteins

1. translated

2. released into lumen

3. folding

4. mature and active protein

true or false

true

2. transmembrane protein

are ……1… translocated across the ER membrane and become ………2.

1. partly

2. embedded in it

2. transmembrane protein

are destined to ……. what (what happens to them their destination)

reside in the membrane of one of these organelles or in the plasma membrane

2. transmembrane protein

in the water soluble protein the ER signal sequence was located in the amino end and here where is it located

in the middle of the protein

2. transmembrane protein

destination of the ER signal sequence

translocon channel

2. transmembrane protein

here we have an additional sequence called what

signal stop sequence

2. transmembrane protein

where is the location of the signal stop sequence

also in the middle of the protein

2. transmembrane protein

what happens when this stop sequence is placed in the translocon channel

( both stop and start (ER signal sequence) are in the translocon channel)

translation STOPS

2. transmembrane protein

in the water soluble protein the ER signal sequence is removed from the final protein in this case are both the signal sequences removed ?

both the signal sequences remain in the final structure

2. transmembrane protein

what happens when we have 1 start and 1 stop signal

we get a double pass transmembrane protein

2. transmembrane protein

what happens if we have 2x start and 1xstop signals

we produce a multiple pass protein (3 passes)

2. transmembrane protein

if we want a protein that crosses the membrane 4 times what do we need

• 2x start

• 2x stop

read

done

read

done

rough reticulum - GLYCOSYLATION

what is glycosylation

addition of carbohydrates

rough reticulum - GLYCOSYLATION

glycosylation is the addition of carbohydrate but more specifically what type of carbohydrate

oligosaccharide

rough reticulum - GLYCOSYLATION

what is oligosaccharides made of

14 monomers (minimum)

rough reticulum - GLYCOSYLATION

oligosaccharide + …1…. = …….2…..

1. protein

2. glycoprotein

rough reticulum - GLYCOSYLATION

we have 2 types of glycosylation what are they

• N-glycosylation

• O-glycosylation

rough reticulum - GLYCOSYLATION

we are going to put carbohydrates into the protein so we need to link what

carbohydrates and amino acids

rough reticulum - GLYCOSYLATION

in the N-glycosylation what functional groups are involved in the linkage

amine group = NH2

alcohol group = OH group

rough reticulum - GLYCOSYLATION

what is bound to what from the protein and from the carbohydrate in N-glycosylation

the amine group (NH2) from the protein is bound to the alcohol group (OH) from the carbohydrate

rough reticulum - GLYCOSYLATION

when we perform N-glycosylation and the NH2 amine group is used, what amino acid is involved

Asparagine (Asn)

rough reticulum - GLYCOSYLATION

O-glycosylation, why is it called O

instead of the amine group alcohol groups are involved

rough reticulum - GLYCOSYLATION

what is the linkage in O-glycosylation

OH (alcohol) from the amino acid/protein and OH (alcohol) from the carbohydrate

rough reticulum - GLYCOSYLATION

what amino acids are involved in O-glycosylation

• Serine (Ser)

• Threonine (Thr)

rough reticulum - GLYCOSYLATION

READ

addition of oligosaccharide (14 monomers) to the protein → residue Asn (N-glycosylation) or Ser, Thr (O-glycoslyation) → Glycoproteins

done

rough reticulum - GLYCOSYLATION

what amino acid is used in

1. N

2. S

glycosylation

1. Asparagine

2. Serine or Threonine