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29 Cards in this Set
- Front
- Back
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What does the RER do in protein synthesis? |
It processes folding and assembly of its own proteins and proteins from other locations |
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What do sugar molecules attached to the ER form? |
Glycoproteins |
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What determines if a polypeptide must enter the ER? |
There's a signal sequence |
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Is the ER stationary |
no it moves around the cell |
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What is protein translocation via? |
The translocon pore |
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When is the N-terminal signal peptide removed? |
When the nascent polypeptide is emerging into the ER lumen |
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How is the ER lumen specialised? |
For... folding assembly modification quality control recycling |
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What processes do proteins undergo to enhance stability before secretion? |
Glycosylation Disulphide bond formation |
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What is the Golgi Apparatus? |
The distribution, shipping (and manufacturing) department for many of the cell's chemical products (proteins, lipids, carbohydrates) eg. cell walls |
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What do protein complexes allow on the Golgi Apparatus? |
they allow vesicles to dock & fuse with their target membrane precisely |
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Name six protein types |
1. serum proteins (eg. albumin - in hepatocytes) 2. extracellular matrix proteins (eg. collagen - in fibroblasts) 3. peptide hormones (eg. insulin - in pancreatic beta islet cells) 4. digestive enzymes (eg. trypsin, amylase - in pancreatic acini) 6. glycoprotein (eg. mucus - widespread) |
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List the four stages of milk secretion |
1. transport of ions and water 2. smooth ER: formation of cytoplasmic lipid vesicle & lipid secretion 3. rough ER: synthesis of milk protein (casein) & vesicle delivery via Golgi - synthesis of lactose from Glc & UDP-Gal occurs in Golgi 4. Vesicular movement (immunoglobins) |
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How do plants store proteins for growth and development? |
In protein bodies (vacuoles) - these provides carbon, nitrogen and sulphur for rapid growth |
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What is ricin? |
It's a potent cytotoxin, an antiherbivory. It is also known as a lectin, found in caster beans |
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Where is ricin stored and what does it do? |
Stored in protein bodies & inhibits protein synthesis by irreversibly inactivating eukaryotic ribosomes - when a seed germinates, ricin is rapidly degraded |
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How is ricin synthesised? |
As a proricin that contains both A & B chains - this proricin is modified within the Golgi then transported to the protein bodies |
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When is ricin catalytically active?
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when it is proteolytically cleared within the protein bodies - so plant avoids poisoning it's own ribosomes |
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What happens to proteins that are incompletely or incorrectly folded (i.e. mutants)? |
they are retained within the ER & targeted for degradation by lysosomes or proteasomes
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what are chaperones (in the ER)? |
they're proteins that assist the correct intracellular folding and assembly of polypeptides |
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what is a cystic fibrosis transmembrane conduction regulator (CFTR)? |
it's a chloride ABC transporter |
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what happens if cystic fibrosis transmembrane conduction regulator in the ER doesn't work sufficiently? |
- epithelia lining sweat gland ducts fail to take up Cl efficiently from the lumen - lack of CFTR allows accumulation of mucus in lungs & pancreas so digestive enzymes can't enter the intestine |
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what is the mutation causing cystic fibrosis in 70% of sufferers |
the mutation results in lack of Pke^508 but doesn't effect channel function |
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what's wrong with quality control checks in the ER regarding cystic fibrosis? |
mutant proteins can't leave the ER so no chloride transporter is present |
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what's the function of lysosomes? |
autophagy, lysis & recycling of misfolded proteins |
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what's the function of vacuoles? |
storage of carbohydrates, organic acids, anthocyanins, seed storage proteins and isolation of toxic substances (maintain internal hydrostatic pressure) |
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how many species are anti herbivory? |
3000 (inc. white clover, flax, almonds, sorghum, wild lima bean & cassava) |
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what is sequenced in the epidermal cells of sorghum leaves? |
the cyanogenic glucoside, dhurrin |
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where are beta-glucosidase and alpha-hydroxynitrilase present in the sorghum leaves? |
beta-glucosidase - in the chloroplasts of underlying mesophyll cells alpha-hydroxynitrilase - in the cytosol of underlying mesophyll cells |
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when does the hydrolysis of dhurrin occur? |
only after tissue disruption by herbivory |
