Largest compartment of the cell by volume

This where intermediary metabolism occurs: synthesis and degradation of small molecules (Ex. glycosylation)

It is also the area where protein synthesis and degradation occurs

Nucleus

Endoplasmic Reticulum

Golgi Apparatus

centrosomes

nucleolus (where ribosomal genes are transcribed)

Membrane bound organelle in eukaryotes

endoctytic membrane transport pathway (from the plasma membrane TO the lysosome)

endocytosis

Oxidative reactons

break down fatty acid chains

catabolism 

digestive enzymes

break down components picked up by the extracellular environment

Size: Pancreatic>Liver

Reason: RER is responsible for the production of SECRETED proteins

Pancreatic < Liver

Reason: liver is responsible for detoxification, which is what the SER is also responsible for 

They are dynamic because they:

Exchange components: lipids and proteins

have to be done in an organized manner

temporarily linked through time 

Remember diagram

Endosome

lysosome/ vacuoles

Golgi apparatus

endoplasmic reticulum

peroxisome (controversial because it is an accessory protein)

Biosynthesis/Secretory pathway

endocytic pathway

proteins and lipids made in ER are delivered to the membranes of other organelles

it is often linked to the secretory pathway

Secreted proteins

contents move out of cell in a:

Regulated way (signal needed, stored in granules)

Constitutive way (constantly released) 

often linked to biosynthesis pathway

Vesicles contents are delivered to the extracellular space

vesicle membrane becomes part of the plasma membrane

plasma membrane forms the vesicle

the vesicle luminal conents come from the extracellular space

small, membrane-enclosed organelle in the cytoplasm and eukaryotic cell

shuttle membrane back and forth in EMS

Contain leaflets: cytosolic and luminal faces

No flipflopping ocurs when forming vesicles

Process:

Donor component will form a vesicle

budding with contents selected for transport

forms a transport vesicle in the cytoplasm

fusion with the target compartment that recieves the contents

Path of a Secreted Protein (Co-Translational)

Translation--> Secretion

1. mRNA arrives in the cytoplasm; translation begins

2. Translocator, which is located on the ER membrane, moves laterally, helping the growning protein cross into the lumen. A signal sequence on growing poplypeptide chain near translocator is required

3. When finished, the signal peptidase binds to the complex and cleaves the signal peptide and it falls off to be degraded

4. Translocator is closed and mature polypeptide chain is in the lumen and everything that was once attached will be released

Provide cell with a short "pulse" of radioactive AA

You follow the path of A as they are incorporated into proteins

- You cannot continuously add radioactive AA as you will have nothing to chase

Gated

Transmembrane

Vesicular

Protein translocators are necessary to transport across membrane

Cytosol to: ER, mitochondria, plastids, peroxisomes

membrane-enclosed transport vesicles ferry proteins from one compartment to another

between: ER-Golgi, Golgi-Late Endosome, Golgi-secretory vesicles

to: Golgi-cell exterior, late endosome-lysosome, early endosome-late endosome, secretory vesicles-cell exterior

- stretch of AA sequence that directs proteins to correct location in the cell

- signal sequence specifies specific destinations

- recognized by sorting receptors that take proteins to their destinations

- often found at N-terminus

- removed by signal peptidase

- can be internal stretches of AA, which remain part of the protein

- hydrophobic

- directs protein to ER

- mRNA has a start-transfer sequence (NH2) and a stop transfer sequence (hydrophobic)

1. Translocator opens (left side for stop and right side for start) and starts moving laterally, growing the polypeptide chain

2. Stop-transfer sequence is reached and signal peptidase cleaves signal peptide

3. Translocator closes and signal peptide is degraded

4. STop-transfer sequence is in membrane while one end (NH2) of mature transmembrane is in ER lumen

*and the other end (COOH; HYDROPHOBIC) is in cytosol 

****For protein with internal SS NH2 could be in the cytosol and COOH in ER (vice versa) 

- protein produced has both hydorphobic start and stop sequence

- translocator moves laterally until stop sequence is reached (NH2 first enters to ER lumen and back out to the cytosol, creating a loop in the lumen)

- both COOH end and NH2 end will be in the cytosol 

- translocator closes and no peptidase signal is used

- start/stop sequence are fused in the membrane

1. Cytosol-->ER

2. ER--> Golgi (where glycosylation of lipds and proteins occur)

3. Golgi-->PM

- Cis face of GA faces the ER

- trans face faces the rest of the cell 

These faces have a lot of interconnections going on

Starts in the ER: single type oligosaccharaide is attached to many proteins

- complex oligosaccharide processing required for mature proteins occurs in the Golgi 

Golgi: a multistage processing unit where different enzymes are located in each cisterna

- each protein is inserted into the membrane in the ER in a specific manner

- result of the process of membrane insertion

- protein asymmetry maintained through vesicular transport

Endocytosed material are found in the early endosome

Lysosomal proteins are delivered from the golgi through vesicles

Lysosomal proteins are found in heterogenous compartments.

There are pacman molecules (digestive enzymes) that consume materials inside the cell and this becomes an endolysosome and they consume all the parts until i tjust becomes a lyysosome. This lowers the pH 

 - low pH requirement of lysosomal enzymes which protects contents of cytosol from digestion

- lysosomal membrane proteins are glycosylated to protect them from porteases in the lumen

- transport proteins in the lysosomal membrane transfer the products of digestion out of the lysosome to the cytosol 

- lysosomeal proteins from ER and golgi are incorporated into endosomes at different stages

- 

30-90% of cell volume

diverse

involed in digestion, nutrient staoge, wate storage, incrasing cell size and turgor pressure

- large increase in volume of plant cell wall without volume of cytosol 

waste to have large volume of cytoplasm 

- vacuole pushes cytoplasm against wall

- uses molecular oxigen to oxidise organic molecules

- oxidative reactioins produce H202

H202 is toxic; degraded in peroxisomes

- break down of fatty acid chains

Formation of Peroxisomes

1. proteins imported from the cytosol insert into the ER

2. Budding occurs and peroxisomal precurssor vesicle forms

3. growth by uptake of specific peroxisomal proteins and lipids from the cytosol

4. peroxisome forms

5. more proteins come in

6. separate through fission 

Post: proteins synthesized in cytosol before sorting. They are unfolded in mitochondria and plastids where HSP70 keeps it unfolded. Folded in peroxisomes and nucleus

Co: synthesized in ER, proteins with ER signal sequence associated with ER during protein synthesis

- protein with an intact nuclear import signal is found in the nucleus

- when signal is mutated or deleted, then protein stays in the cytosol