The secretory pathway is arguably one of the most important pathways in the body. It deemed ‘Secretory’ primarily because it’s the pathway that controls how the cell secretes proteins int extracellular environment.
This pathway involves a few main players – the Endoplasmic reticulum (ER), Golgi Apparatus and the Lysosome. Let’s dig a bit deeper into the role and functions of each of these organelles below.
After transcription (DNA --> RNA) in the nucleus and translation (RNA --> protein) in the ribosome, a new protein product is formed. What does this new protein product want to do next? It wants to become biologically active. How does it do so? By folding! What helps fold these proteins? Chaperones! Where does this folding take place? The endoplasmic reticulum!
Proteins are imported into the ER using a signal sequence (seen on the newly made protein). This sequence is bound by a signal recognition particle (SRP). This creates a SRP – ribosomal protein complex. This SRP-ribosomal protein complex binds to the SRP receptor on the ER. This binding releases SRP and allows our signal sequence to enter the ER.
The endoplasmic reticulum (rough) can be thought of as the main protein folding and quality control apparatus. It’s here that translated proteins from the ribosome can be twisted and turned to properly function. It’s also where mis/unfolded proteins can be dealt with (sent or tagged for degradation).
After folding is complete in the ER, our folded protein exits the ER in lipid vesicles and head toward the cis side of the Golgi Apparatus. Here, proteins are modified and packaged into transport vesicles to their final destination (essentially, where they’ll be working in the cell).
Digestive enzymes (proteins) are packaged and pinched off into a specific type of vesicle. That vesicle is a lysosome! These lysosomes are packed with a digestive punch and work to break down complex molecules inside the cell.
For more practice, try understand what happens when certain parts of this pathway are disrupted. This will help drive home the interconnectedness of these organelles and larger function. Happy studying!
Njia ya secretory ni bila shaka moja ya njia muhimu zaidi katika mwili. Inachukuliwa "Secretory" hasa kwa sababu ni njia ambayo inadhibiti jinsi seli secretes protini int mazingira ya nje ya seli. Njia hii inahusisha wachezaji wachache kuu - Endoplasmic reticulum (ER), Golgi Apparatus na Lysosome. Hebu kuchimba kidogo zaidi katika jukumu na kazi ya kila moja ya organelles hizi chini. Baada ya maandishi (DNA --> RNA) katika kiini na tafsiri (RNA --> protini) katika ribosome, bidhaa mpya ya protini hufanyizwa. Bidhaa hii mpya ya protini inataka kufanya nini baadaye? Inataka kuwa hai. Inafanya hivyo jinsi gani? Kwa kukunja! Ni nini husaidia kuiga protini hizo? Waandamanaji! Ufungaji huo hufanywa wapi? Mfumo wa endoplasmic! Protini huingizwa katika ER kwa kutumia mfululizo wa ishara (kuonekana kwenye protini mpya iliyotengenezwa). Mfuatano huu ni amefungwa na ishara utambuzi chembe (SRP). Hii inaunda SRP <unk> ribosomal protini tata. SRP-ribosomal complex ya protini huunganisha na receptor ya SRP kwenye ER. Hii binding releases SRP na inaruhusu mfululizo wetu ishara kuingia ER. Endoplasmic reticulum (rough) inaweza kufikiriwa kama kuu protini folding na ubora wa kudhibiti kifaa. Ni hapa kwamba protini zilizotafsiriwa kutoka ribosome zinaweza kupotoshwa na kugeuzwa kufanya kazi vizuri. Pia ni ambapo mis-unfolded protini inaweza kushughulikiwa (kutumwa au alama kwa ajili ya uharibifu). Baada ya kuunganishwa kwa damu, protini yetu ya folded hutoka kwenye ER katika vesicles ya lipid na kuelekea upande wa cis wa Golgi Apparatus. Hapa, protini ni iliyopita na pakiti katika vesicles usafiri kwa marudio yao ya mwisho (kimsingi, ambapo wao itakuwa kufanya kazi katika kiini). Enzyme za kumeng'enya chakula (protein) hufungiwa na kufungwa katika aina fulani ya kibofu. Kibofu hicho ni lysosome! Lysosomes hizi zimejaa punch ya kumeng'enya na hufanya kazi ya kuvunja molekuli tata ndani ya chembe. Kwa mazoezi zaidi, jaribu kuelewa nini hutokea wakati sehemu fulani za njia hii zinapovurugwa. Hii itasaidia kuendesha nyumbani interconnectedness ya organelles hizi na kazi kubwa. Mafunzo yenye furaha!