lecture 5 - endomembrane system Flashcards
How is the endomembrane system interconnected?
By vesicles which move between the organelles
What are the key organelles of the endomembrane system?
Nuclear envelope, endoplasmic reticulum (smooth and rough), golgi apparatus, vesicles, lysosome, vacuoles, plasma membrane
What is the structure of the endoplasmic reticulum (ER)
A series of flattened sacs, connected by tubules, and divided into two regions (smooth and rough).
What are the spaces within the ER?
lumen
What are the key functions of the smooth ER?
Metabolises carbohydrates, synthesise lipids for membranes, detoxificate toxins, store calcium ions.
Is the amount of sER in a cell fixed?
No - it can change to fit cell function requirements.
Does the sER contain ribosomes?
No
Why does the rER have a rough appearance?
It has ribosomes.
What is the function of ribosomes?
They synthesise proteins in the rER
Where are proteins processed in the rER?
In the lumen
Where does synthesis of cytoplasmic proteins occur?
The free ribosomes
How do proteins leave the ER?
In vesicles that ‘bud off’ the surface of the ER.
What is the main function of the golgi?
Receive, sort and distribute proteins from the rER.
What are the two faces of the golgi?
Cis and trans face
What part of the golgi do vesicles arrive at?
The cis face
Where do processed vesicles leave the golgi?
The trans face
What is glycosylation, and where does it occur?
Addition of carbohydrates to, or modification of, proteins, in the golgi
What do golgi produce?
Polysaccharides
How does the golgi sort proteins?
By adding markers to the proteins that direct them to the appropriate vesicles for transport.
How does the golgi direct leaving vesicles?
Vesicles leaving the trans face are tagged with short proteins that direct them to the targets, and act as ‘docking sites’ when they get there.
What is bulk transport?
A process that allows lots of substance to pass through the cell membrane, in one place, at the same time
What is exocytosis?
The process of transporting glycoproteins out of the cell into the extracellular matrix via vesicles.
What is constituitive exocystosis?
A continuous default process, where proteins are transported to the extracellular matrix.
What is regulated exocytosis?
The release of hormones and neurotransmitters from the cell, only when the required signal is received.
What is endocytosis?
The transport (in bulk) of molecules and particles into the cell from the extracellular matrix.
What is phagocytosis?
The process in which food vacuoles absorb and break down food or bacteria particles with the aid of lysosomes.
Where does phagocytosis occur commonly in humans?
In macrophages, a type of white blood cell, which attacks bacteria.
How do macrophages kill bacteria?
They engulf detected bacteria (which release proteins that attract macrophages), trap them in the phagosome, and break them down using enzymes from lysosomes.
What is pinocytosis?
The process in which vesicles ‘drink up’ extracellular fluid, and take with it various solutes into the cell.
What is the function of the coat protein in pinocytosis?
Aids in the formation of the up-take vesicle
Why is pinocytosis non-selective?
Any solutes dissolved in the extracellular fluid captured will be brought into the cell.
What is receptor-mediated endocytosis?
A specialised form of pinocytosis, in which receptors in vasicles bind to and capture specific solutes from the extracellular fluid and bring them into the cell.
Where are lysosomes made?
The rER. (rough endoplasmic reticulum) and golgi body. rER makes proteins that create the lysosome enzymes. These enzymes are then enclosed by vesicles from the golgi complex
How do lysosomes aid food vacuoles?
They fuse with the vacuoles, passing on their digestive enzymes.
What feature of the lysosome keeps the enzymes active?
Acidic interior
What is autophagy?
When lysosomes digest and recycle unwanted cellular material.
How is programmed cell death facilitiated?
Through lysosomal digestion of organelles.
Where are vacuoles derived from?
the rER and golgi. ( in plants, the vacuole is formed when vesicles from the rER and golgi merge together)
What is the function of the central vacuole in plant cells?
The perform lysosome-like fucntion and are able to absorb water to allow the cell to grow without the need for a large increase in the amount of cytoplasm.
What is the size of a ribosome?
25-30nm
What are the enzymes used by lysosomes?
Hydrolytic enzymes
How are phospholipids delivered to the cell membrane?
Via exocytosis
