Animal Cells (Part Three) Flashcards
Give the organelles/cellular compartments that are involved in the endomembrane system.
- Nucleus
- Endoplasmic reticulum
- Golgi Apparatus
- Lyosome/Vacuole
- Endosomal compartments
- Transport vesicles
Give the 3 types of trafficking pathways.
- Biosynthetic-secretory
- Endocytic
- Retrieval-recycling
Give the organelles/cellular compartments involved in retrieval-recycling trafficking pathways.
- Endoplasmic reticulum
- Golgi Apparatus
- (Late and early) endosomes
- Transport vesicles
Give the organelles/cellular compartments involved in endocytic trafficking pathways.
- (Late and early) endosomes
- Lyosomes (Vacuole)
- Transport vesicles
What percentage of membranes in the cell are the membrane sacs and branched tubules of the endoplasmic reticulum?
~50%
Give the functions of the smooth ER.
- Calcium storage (for cell signalling)
- Lipid synthesis
- Detoxification of drugs/poisons
- Metabolism of carbohydrates
What is the function of the rough ER?
Processing of secretory proteins.
Give the steps to cotranslational translocation in the ER.
- Ribosome assembles and binds mRNA.
- If polypeptide contains a signal sequence, it is targeted to the ER membrane.
- The signal peptide is cleaved off and the protein is translated into the ER lumen where it is folded and further processed.
- Cytosolic proteins can contain signal sequences target them to other organelles.
Name the parts of the Golgi apparatus in order from where transport vesicles arrive to where secretory vesicles exit.
- cis face
- cis Golgi network
- cis Cisterna
- medial Cisterna
- trans Cisterna
- trans Golgi network
- trans face
Give four functions of an oligosaccharide.
- Provides protection against pathogens (e.g. the mucus coating on the epithelia)
- Serves in cell-cell recognition and signalling
- Marks progression of the protein
- Aids folding and interaction with other proteins
What happens in the Golgi?
- Oligosaccharide chains are processed
- Proteoglucans are assembled
What do most proteins that arrive from the ER at the cis face Golgi contain?
An N-linked oligosaccharide
Describe the processing that occurs to oligosaccharides at each area of the Golgi.
- cis Golgi network: phosphorylation of oligosaccharides on lyosomal proteins
- cis Cisterna: removal of Mannose.
- medial Cisterna: removal of Mannose, addition of GlcNAc.
- trans Cisterna: addition of Galactose, addition of NANA.
- trans Golgi network: sulfation of tyrosines and carbohydrates.
What percentage of eukaryotic proteins are glycosylated?
~50%
What is meant if an oligosaccharide is
a) N-linked?
b) O-linked?
a) N-linked = linked to Asparagine.
b) O-linked = linked to Threonine.
Give the 3 types of endosomes involved in processing endocytosed material.
- early endosome
- recycling endosome
- late endosome
Give the steps to membrane trafficking along the endocytic pathway.
- Vesicle formation at plasma membrane.
- Fusion of vesicle with early endosome.
- Decision made: degradation or recycling?
- Recycling occurs via recycling endosome
- Early endosome matures into late endosome
- Recycling from late endosome to Golgi.
- Maturation from late endosome into lysosome.
In the endocytic pathway, what is the pH of the:
a) Early endosome?
b) Multivesicular carrier body?
c) Late endosome?
d) Lysosome?
a) Early endosome = 6.5
b) Multivesicular carrier body = 5.5
c) Late endosome = 4.5
d) Lysosome = 4.5
What is the pH inside an acid hydrolase, e.g. protease and lipase?
~5.0
What are the three potential pathways to degradation in lysosomes?
- Phagocytosis
- Pinocytose and receptor mediated endocytosis
- Autophagy
What is the definition of phagocytosis?
The endocytosis of large particles.
What is pinocytosis?
The endocytosis of solved proteins and molecules.
What is autophagy?
The enclosure of cytosol and organelles into an Autophagosome.
What happens to the Autophagosome under cell starvation?
It recycles the cytosol.
