Secretion Flashcards
(23 cards)
Examples of protein secretion in microbes plants and mammals
microbes = fungal sex pheromones
plants = gibberellins
mammals = growth hormone
how do hormones work
secreted by cells
diffuse into extracellular fluid and distributed by the circulatory system
what do hormones do
coordinate anatomical, physiological and behavioural changes in an animal
where is the growh hormone secreted
anterior pituitary
where do growth hormones act and stimulate
Act = tissues
Stimulate:
-cells to take up amino acids
-liver produce insulin = bone and cartilage growth
what is the result of overproduction and underproduction of growth hormones in children
overproduction = gigantism
underproduction = pituitary dwarfism
what do plant embryos secrete
gibberellins = plant hormone
what do gibberllins change, synthesis and secrete
-changes in aleurone layer
= synthesis and secretion of enzymes that digest proteins and starch in endosperm
what happens to gibberellins that develop form seeds
diffuse out into immature fruit tissue
what does gibberellin A1 control
plant stem elongation
treating dwarf plants with the hormone restores normal growth
what do sex pheromones do
allow fungi to recognise cells of the opposite mating type
promote mating
e.g. yeast alpha factor
yeast alpha-factor, what is it, what is it secreted and detected by
short peptide
secreted from yeast alpha cells
detected by yeast a cells
promotes mating of a and alpha cells
what happens to proteins after translation
many proteins are transported from the cytoplasm to another cellular compartment
intracellular and extracellular compartment targets/ secretes
intracellular compartment is targeting nucleus, mitochondrion, lysosome and chloroplast
extracellular compartment secretes periplasm, cell wall, bloodstream
Where do proteins traverse from (secretory pathway)
endoplasmic reticulum -> golgi apparatus -> vesicles -> secretion or lysosomes
What do secreted proteins contain
circa 25 amino acid
N-terminal signal sequence
what do polypeptide sequences contain
signals that indicate where in the cell polypeptides belong
What happens during translation
1) signal sequence binds to Signal Recognition Particle (SRP)
2) Translation paused
3) SRP-ribosome complex docks on ER receptor
4) Membrane channel opens
5) SRP leaves complex
6) Translation resumes, protein co-translationally translocated into lumen of ER
7) N-terminal signal sequence cut off
8) Co-translational translocation continues into ER (Protein continues moving into ER)
9) Chaperonins fold protein
10) Translation ends, polypeptide fully released in ER
what sorting events do other signals direct proteins for
allow protein to stay in ER
form glycoproteins by adding sugars to golgi apparatus that go to lysosomes or plasma membrane
what happens to proteins with no further signals
go through golgi apparatus and are secreted from the cell
where are most proteins modified
after translation
WHat are the three types of modifications to proteins
proteolysis (cleaving)
Glycosylation (adding sugars)
Phosphorylation (adding phosphate groups)
