cell structure Flashcards
what is the endomembrane system
a membrane system interconnected by direct physical contact or transfer between each using vesicles
(includea all organelles)
what are the three steps in making proteins?
synthesis in the ER
tag and package by the Golgi apparatus ti put the right proteins into the right place
delivery by vesicle transport which can fuse with the membrane of the cells or the organelles in the cell
what is the endoplasmic reticulum composed of
the smooth ER and the rough ER
continuous with the nucleic envelope
features of the smooth ER
- metabolising carbohydrates and sythesis of lipids
- detoxification of drugs and poisions
- storage of calcium ions from signals in cell
- the more active the cell the more extensive the sER (this can increase or decrease on need)
features and functions of the rough ER
- looks rough due to ribosomes
- secreted and memrbane bound proteins enter the lumen (interior) to be processed from the cell or to the cell membrane passing through golgi first.
where are cytoplasmic proteins synthesised
on free ribosomes (NOT IN THE rER)
what does it mean that the Golgi complex has polarity?
the golgi has a cis face and trans face
when vesicles from the er arrive they come to the cis face get processed and then leave the trans face
what is the composition of the golgi
series of membrane sacks and ascociated vesicles
what is glycosylation
addition of carbohydrates to proteins (happens in golgi lumen (middle))
important for secreted or cell surfae proteins
e.g. pectin and hemicellulose
how does the golgi sort proteins
molecular markers are added to direct proteins to the correct vesicles before budding at the trans face
for example phosphorylated (mannose 6 - phosphate) sugar identifies protins that will become lysosomal enzymes so the suagr acts as a tag for the vesicle to know where to take it.
what is another important function if the tagging if proteins
they act as a docking site when the reach the target
what are the different types of vesicles
transport vesicles
secretory vesicles
vacuoles
artificial vesicles called liposomes used ti administer drugs and vaccines
describe exocytosis
transport of materical out of the cell or to the cell surface
- constitutive exocytosis: releases ECM proteins, is unregulated, giving out things that make up the ECM
- regulated exocytosis: releaes hormones and neurotransmitters, is controlled so will only happen from signalling events
describe endocytosis
cells uptake of molecules and particulate matter at the plasma membrane in otder to perform its processes
describe phagocytosis
cells uptake of ‘food’ particles (solids)
membrane forms pseudopodium (arms) and wraps around particle and form a food vesicle that is then brought into the cell to be transported and used (digestion by lysosomes)
can also engulf and destroy bactera
describe pinocytosis
cell drinking fluid with solutes n it
uptake of extracellular fluid containing things like proteins and sugars
upatke vesicle formed using coat protein to signal to the membrane to bud inwards to create a dip for the fluid to go into and then form a vescicle
- non selective uptake
describe receptor - mediated endocytosis
specialised pinocytosis which uses membrane proteins to form a vesicle where the proteins can bind to the solutes that are wanted and get enough in the cell
this allows the cell to take in bulk numbers of specific substances that could be low conc in the ECM
breifly describe lysosomes
membrane bound organelles made by rER and golgi that contain hydrolytic enzymes used to break things down
acidic interior allows enzymes to be active
degradation of proteins, lipids, carbs and nucleic acids which can be recycled into the cell or expelled
essential for normal functioning of the body
describe vacuoles
large vesicles derived from the rER and golgi
- can perform lysosome-like activity
digestive fnctions and water absorbtion (allow plant cells to grow)
in plants large central vacuole absorbs water which is integra for plant cells
