Endomembrane System and Bulk Transport Process Flashcards
Lecture 5
What does the endomembrane system include?
- Nuclear envelope
-Endoplasmic reticulum (smooth and rough) - Golgi apparatus
- vesicles
-Lyososomes
-Vacuoles
-Plasma membrane
What is the endomembrane system
A membrane system interconnected by directed physical contact or transfer by vesicles
How to move proteins out of the cell
- Synthesise
-Tag and package
-Deliver
When you move proteins out of the cell by delivering it,
vesicles transport proteins and cause fuse with membrane of organelles/ the cells
Synthesis occurs in
the endoplasmic reticulum
The endoplasmic reticulum..
is composed of two regions which is the smooth and rough endoplasmic reticulum.
Tag and package occurs in
the golgi apparatus
First three functions of the smooth endoplasmic reticulum
- Metabolism of carbohydrates
- Lipid synthesis for membranes
- Detoxification of drugs and poisons
Second three functions of the smooth endoplasmic reticulum
- Storage of calcium ions used as a signal in the cell
- Extensive smooth endoplasmic reticulum in cells active in these processes
- The amount of smooth endoplasmic reticulum can be increased or decreased to meet demand
First Two functions of rough endoplasmic reticulum
- Rough appearance due to ribosomes
- Involved in protein synthesis
Second two functions of the rough endoplasmic reticulum
- Secreted and membrane bound proteins enter the lumen which is the interior of the rough endoplasmic reticulum
- and are processed by the rough endoplasmic reticulum and the rest of the endomembrane system for release from the cell or retention on the cell membrane
The golgi complex
Series of membrane sacs and associated vesicles
Function of the golgi complex
Receives, modifies, sorts and ships proteins arriving from the rough endoplasmic reticulum
The golgi complex has polarity.
- Vesicles form endoplasmic reticulum arrive at the cis face
-Processed vesicles leave at the trans face
Glycosylation
- Addition or modification of carbohydrates to proteins
-Important for secreted or cell surface proteins - Golgi also produces many polysaccharides which may also be secreted from the cell
Sorting proteins
- Adds molecular markers to direct proteins to the correct vesicles before “budding” from the trans face
Directing vesicle trafficking 1
- Adds molecular tags to vesicles leaving the trans face to direct them to the correct targets
- The tags are often short proteins exposed on the vesicle surface
Directing vesicle trafficking 2
- Tags direct vesicles to lysosomes, or secretory pathways, or to plasma membrane to add to membrane proteins
-Act as docking sites when they reach their target
Artificial vesicles (liposomes) can be used for..
drug and vaccine delivery
types of vesicles
Membrane bound (lipid bilayer), cytoplasm filled organelles
Names reflect function:
- Transport
- Secretory
- Vacuoles
Exocytosis
Transports material (glycoproteins) out of the cell or delivers it to the cell surface
Bulk transport across the plasma membrane
- Exocytosis
-Endocytosis - Phagocytosis
- Pinocytosis
-Receptor mediated endocytosis
Two types of exocytosis
- Constitutive exocytosis
-Regulated exocytosis
Constitutive exocytosis
Releases extracellular matrix proteins
Regulated exocytosis
Reles hormones and neurotransmitters
Endocytosis
The cell takes in molecules and particulate matter at the plasma membrane
Phagocytosis
- Cell eating
- Uptake of food particles
- Forms a phagocytic vacuole which is digested by the lysosomes
- In humans this occurs in macrophages
Pinocytosis
- Cell drinking
- Uptake of extracellular fluid containing various solutes such as protein and sugars
- Up takes vesicles is formed with the aid of a coat protein
- Up take is non-selective
Receptor mediated endocytosis
- Specialised from of pinocytosis
- Allows the cell to take up bulk quantities of specific substances which may be present at only low concentrations in the extracellular fluid
- Receptor proteins are used to selectively capture the required solute
Phagocytic vacuoles fuse with…
lyososomes
Lysosomes are
membrane bound organelles made by the rough endoplasmic reticulum and golgi body containing hydrolytic enzymes
The interior of a lysosomes is acidic which is required for..
the enzymes to be active
What is required for enzymes to be active
The interior of a lysosomes should be acidic
Lysosomes degrade..
proteins, lipids, carbohydrates and nucleic acids and release breakdown products into the cell
Lysosomes digest and recycle..
unwanted cellular materials
Autophagy is important for cell health. What is it?
Lysosomes digest and recycle unwanted cellular materials
Lysosomal digestion is also important in..
programmed cell death in which whole cells “intentionally” die
Defects in lyososomal enzymes can result in..
lysosomal storage diseases
Food vacuoles are involved in..
phagocytosis
Why are vacuoles important in plants
- Can perform lysosome like functions
- The large central vacuole absorbs water allowing plant cells to grow without a large increase in cytoplasm
Vacuoles are usually the..
largest compartment in a plant cell
