CELS 191 Lecture 4 Flashcards
what is included in the endomembrane system
the nuclear envelope
the endoplasmic reticulum - smooth and rough
Golgi apparatus
vesicles
lysosomes
vacuoles
plasma membrane
is the endoplasmic reticulum’s membrane continuous with the nuclear envelope
yes
what is the difference between the smooth and rough ER
the rough ER contains ribosomes (this is what makes it appear rough)
what is the function of the rough ER
the rough ER is involved in protein synthesis due to the presence of ribosomes. secreted and membrane bound proteins enter the lumen of the RER and are processed by the RER and the rest of the end-membrane system for release from the cel or retention on the cell membrane
what are the functions of the smooth ER
metabolism of carbohydrates
lipid synthesis for membranes
detoxification of drugs and poisons
storage of calcium ions (used as a signal to control cellular processes
is the amount of SER always the same
no, the amount of SER changes depending on the cell and its function. for example liver cells have lots of SER because they are involved in detoxifying
what is the Golgi complex composed of
membrane sacs and associated vesicles
what is the function of the Golgi complex
it is responsible for receiving, modifying, sorting and shipping proteins for the rough ER.
why do we say the the Golgi has polarity
because it has two sides to it. the cis face receives vesicles from the rough ER and the trans face is where processed vesicles leave from
what are the functions of the Golgi complex
glycosylation, sorting proteins, directing vesicle trafficking
what is glycosylation
this addition or modification of carbohydrates to proteins. this is important for secreted or cell surface proteins. the Golgi also produces many polysaccharides which may also be secreted from the cell
how does the Golgi sort proteins
by adding molecular markers to direct proteins to the correct vesicles before budding form the trans face
how does the Golgi direct vesicle trafficking
by adding molecular tags to vesicles leaving the trans face to direct them to the correct targets. such tags are often short proteins exposed on the vesicle surface. tags direct vesicles to lysosomes, or secretory pathways, or to the plasma membrane to add membrane proteins. they also act as docking sites when they reach their targets
what are vesicles
membrane bound, cytoplasm filled organelles
what are the three types of vesicles
transport vesicles (used to transport substances such as proteins from place to place), secretory vesicles (used to secrete substances) and vacuoles.
what are the two methods from bulk transport across the membrane
exocytosis and endocytosis
what is exocytosis
when material (glycoproteins) are transported out of the cell or delivered o the cell surface
what are the two types of exocytosis
constitutive exocytosis (release ECM proteins without the need for a signal) and regulated exocytosis (releases hormones and neurotransmitters after receiving a signal from the cell)
what is endocytosis
when the cell take in molecules and particular matter at the plasma membrane
what are the two types of endocytosis
phagocytosis and pinocytosis
what is phagocytosis
colloquially called cell eating it is the uptake of food particles which are usually large and solid
how does phagocytosis occur
the membrane forms a phagocytic vacuole which is digested by the lysosomes the “arms” wrap around the for particle and fuse together when they touch so the plasma membrane is never broken
what is pinocytosis
colloquially called cell drinking it is the uptake of fluid containing various solutes such as proteins and sugars - the uptake is formed with the aid of a coat protein and in non-selective meaning the cell cannot control what comes in
what is receptor mediated endocytosis
this is a specialised form of pinocytosis which allows the cells to take up bulk quantities of specific substances which may only be present in low concentrations in the extracellular fluid
