Ch. 12 - The Endomembrane System (Homework Set)

What protein complex or complexes provide initial recognition of the vesicle with the target membrane? -t-SNAREs and v-SNAREs -Rab GTPase -multisubunit tethering proteins and coiled-coil tethering proteins -NSF and SNAPs

multisubunit tethering proteins and coiled-coil tethering proteins

Which of the following statements is false regarding phagocytosis? -It is mediated by clathrin at the plasma membrane. -It involves the projection of pseudopods. -It is used by macrophages and neutrophils to ingest bacteria. -It is used by amoebae to ingest food. -It can ingest large particles.

It is mediated by clathrin at the plasma membrane.

Which of the following cellular processes may be inhibited in tumor cells? -LDL degradation -caveolae uptake -N-linked glycosylation -catalase activity -autophagy

autophagy

In the Golgi complex, __________. -the anterograde transport system is used to move vesicles back to the ER -proteins are synthesized -proteins are N-glycosylated -carbohydrate side chains of glycoproteins are modified

carbohydrate side chains of glycoproteins are modified

A researcher is attempting to isolate rough ER microsomes using ultracentrifugation. Which of the following would indicate contamination of the rough ER with another organelle? -ribosomes -glycosylated prot -membranes -catalase

catalase

Which of the following molecules forms the coat during receptor-mediated endocytosis-coated pit formation? -mannose-6-phosphate -clathrin -caveolin -T-SNARE -tethering protein

clathrin

The continuous release of mucus by the epithelial cells lining the respiratory tract is an example of... -clathrin-coated pit formation. -phagocytosis. -regulated secretion. -constitutive secretion. -the mucus response.

constitutive secretion.

All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the cytosol, while others are bound to the surface of the endoplasmic reticulum. Most proteins made by free ribosomes function in the cytosol. Proteins made by bound ribosomes either function within the endomembrane system or pass through it and are secreted from the cell. Which of the following proteins are synthesized by bound ribosomes? (more than one answer can be chosen) -DNA polymerase -actin -insulin -ribosomal protein -ER protein -lysosomal enzyme

-insulin -ER protein -lysosomal enzyme

A COPII-coated vesicle has all of the following except... -AP-2. -Sec 13/31. -Sec 23/34. -Sar1. -v-SNARE.

AP-2.

The low pH of lysosomes is established by... -superoxide dismutases. -acid hydrolases. -ATP-dependent proton pumps. -catalases. -\betha-glucuronidases.

ATP-dependent proton pumps.

Each of the following is an endoplasmic reticulum function except... -the export of protein that cannot be folded into the cytoplasm for destruction. -peptide folding. -addition of carbohydrate to proteins to make glycoproteins. -the assembly of multimeric proteins. -All are endoplasmic reticulum functions.

All are endoplasmic reticulum functions.

Each of the following is a component involved in the SNARE hypothesis model mechanism except... -tethering complex. -NSF protein. -v-SNARE. -Rab GTPase. -All are involved.

All are involved.

Botulinum toxin blocks neuromuscular transmission, causing paralysis. How does it do this? -Botulinum toxin cleaves the t-SNARE, blocking fusion of the vesicle. -Botulinum toxin blocks the GTPase activity of Rab. -Botulinum toxin cleaves the tethering proteins, inhibiting accumulation at the membrane. -Botulinum toxin inhibits NSF, blocking the regeneration of SNAREs.

Botulinum toxin cleaves the t-SNARE, blocking fusion of the vesicle.

In a lysosomal storage disease, newly synthesized lysosome hydrolases are secreted from the cells rather than being delivered to the lysosomes. What is one possible mechanism for this result? -Mannose is not phosphorylated in the cis-Golgi network. -Lysosomal enzymes are not phosphorylated in the rER. The ER is unable to produce lysosomal vesicles. -The cis-Golgi network lacks a proton gradient. -All the hydrolase genes are mutated, resulting in synthesis by ribosomes free in the cytoplasm rather than on the endoplasmic reticulum membrane.

Mannose is not phosphorylated in the cis-Golgi network.

The endoplasmic reticulum is a site for... -addition of lipid residues. -potassium storage in muscle cells. -degradation of foreign material brought into the cell by phagocytosis. -drug detoxification by catalase. -N-linked glycosylation of polypeptides.

N-linked glycosylation of polypeptides.

For each of the following statements, indicate if it is true of the rough ER only, of the smooth ER only, of both rough and smooth ER, or of neither. -has ribosomes attached to its outer (cytosolic) surface -Is involved in the breakdown of glycogen -is the site for the folding of membrane-bound proteins -contains less cholesterol than does the plasma membrane -tends to form tubular structures -is involved in the detoxification of drugs -visible only by electron micrscopy -usually consists of flattened sacs -is the site for biosynthesis of secretory proteins

ROUGH ER: -Has ribosomes attached to its outer (cytosolic) surface -Is the site for the folding of membrane-bound proteins -usually consists of flattened sacs -Is the site for biosynthesis of secretory proteins SMOOTH ER: -Is involved in the breakdown of glycogen -Tends to form tubular structures -Is involved in the detoxification of drugs ROUGH & SMOOTH ER: -Contains less cholesterol than does the plasma membrane -Visible only by electron microscopy

What is the role of Rab GTPase in the process? -Rab GTPase locks the t-SNARE and v-SNARE together, facilitating fusion of the vesicle. -Rab GTPase helps to disconnect t-SNARE and v-SNARE after fusion has occurred. -Rab GTPase causes the fusion of the vesicle to the target membrane. -Rab GTPase facilitates the initial binding of t-SNARE to v-SNARE.

Rab GTPase locks the t-SNARE and v-SNARE together, facilitating fusion of the vesicle.

The various parts of the endomembrane system serve different functions in the cell. Identify the roles of each part of the endomembrane system (smooth ER, rough ER, Golgi apparatus, lysosomes) -protein synthesis -protein modification and sorting -macromolecule digestion -lipid synthesis -authophagy -cisternal maturation -calcium ion storage -poison detoxification

SMOOTH ER: -lipid synthesis -poison detoxification -calcium ion storage ROUGH ER: -protein synthesis GOLGI APPARATUS: -protein modification and sorting -cisternal maturation LYSOSOMES: -macromolecule digestion -autophagy

A patient was diagnosed to possess a mutation in an ER-resident protein in which the ER-signal sequences of the protein were inappropriately deleted and instead replaced with a mannose-6-phosphate during protein synthesis and posttranslational modification. What is the likely fate of this mutant protein? -The protein would not be glycosylated. -The protein would be targeted to the lysosomes. -The protein never enters the Golgi complex. -The protein would be secreted by exocytosis.

The protein would be targeted to the lysosomes.

Consider the mechanism of Botulinum toxin. Is this toxin reversible? -Yes, however the cell must regenerate new t-SNAREs. -No, Botulinum toxin damage results in atrophy of the neuron and neuron death. -Yes, it will reverse when the concentration of Botulinum toxin decreases. -No, Botulinum toxin causes permanent damage to the nerve terminal.

Yes, however the cell must regenerate new t-SNAREs.

The mannose-6-phosphate receptor would have what type of protein tag? -a cis-Golgi retention tag -a KDEL ER retention tag -a lysosomal targeting tag -a trans-Golgi retention tag

a trans-Golgi retention tag

Using genetic engineering techniques, which of the following would you do to a protein that normally is constitutively secreted to make it accumulate in the ER? -mutate one of the asparagines that is normally glycosylated to an alanine, which is not glycosylated -add a KDEL sequence near its C-terminus -fuse it to GFP -add an amino acid that would get a mannose-6-phosphate group added to its carbohydrate -None of these would cause the protein to accumulate in the ER.

add a KDEL sequence near its C-terminus

In which of the following organelles would you expect to first find a protein destined to be secreted from a cell? -endoplasmic reticulum -endosome -secretory vesicle -lysosome -Golgi apparatus

endoplasmic reticulum

When a membrane protein is radioactively labeled during synthesis and followed through the various organelles in the secretory pathway, all the radioactivity is concentrated in the cis-Golgi apparatus six hours after the protein synthesis. This suggests that the protein... -has a membrane-spanning domain length equals the thickness of the cis-Golgi membrane. -has a mannose-6-phosphate tag. -is misfolded and being degraded in the cis-Golgi. -contains a KDEL sequence near its C-terminus. -was imported directly into the cis-Golgi posttranslationally.

has a membrane-spanning domain length equals the thickness of the cis-Golgi membrane.

What is another likely role of the SNARE mechanism of vesicle fusion, in addition to secretion of material? -insertion of membrane proteins into the plasma membrane -sorting of material into secretory vesicles -endocytosing material via pinocytosis -segregation of acid hydrolases into early endosomes

insertion of membrane proteins into the plasma membrane

Comparing cells synthesizing secretory proteins and cells secreting steroid hormones, the cells synthesizing the steroid hormones have... -more smooth ER. -more rough ER. -equal amounts of smooth and rough ER, but fewer lysosomes. -equal amounts of smooth and rough ER, but more lysosomes. -equal amounts of smooth and rough ER.

more smooth ER

The vesicles that are anchored to the plasma membrane at a nerve cell presynaptic site are specialized for... -regulated secretion. -constitutive secretion. -endocytosis. -lysosome secretion. -polarized secretion.

polarized secretion.

Proteins that are secreted from a eukaryotic cell must first travel through the endomembrane system. Put the following items in order to form the path of a secretory protein follows from synthesis to secretion. (not everything will be used) -endoplasmic reticulum -lysosome -plasma membrane -trans Golgi cisternae -cis Golgi cisternae -medial Golgi cisternae -peroxisome

protein synthesis --> endoplasmic reticulum --> cis Golgi cisternae --> medial Golgi cisternae --> trans Golgi cisternae --> plasma membrane --> extracellular space

A protein that is normally localized in the cytoplasm has been engineered so that it will be secreted from the cell instead. Which of the following represents the most likely pathway for the protein after it has been completely synthesized? -cytoplasm \to rER \to Golgi \to secretory vesicle \to environment -rER \to Golgi \to secretory vesicle \to environment -sER \to Golgi \to secretory vesicle \to environment -rER \to secretory vesicle \to Golgi \to environment -rER \to Golgi \to sER \to cytoplasm \to environment

rER \to Golgi \to secretory vesicle \to environment

Uptake of low-density lipoproteins (LDLs) occurs by... -facilitated transport. -receptor-mediated endocytosis. -phagocytosis. -pinocytosis. -simple diffusion.

receptor-mediated endocytosis.

Pancreatic acinar cells produce and store hydrolytic enzymes in zymogen granules until hormones signal the cell to release the enzymes in a process known as... -constitutive secretion. -transport secretion. -intracellular secretion. -consistent secretion. -regulated secretion.

regulated secretion

In receptor-mediated endocytosis, each of the following is a fate for the receptors and/or vesicle contents except... -recycling to the plasma membrane. -transcytosis. -release from the vesicle into the nucleus. -digestion in a lysosome. -All are possible fates.

release from the vesicle into the nucleus.

Statins are drugs that are administered to inhibit the biosynthesis of cholesterol in the liver, and thus are used to lower blood plasma cholesterol levels in order to decrease patient risk of atherosclerosis and associated diseases such as myocardial infarction (heart attack). Which of the following components of the endomembrane system is the site of action of statin drugs? -lysosomes -the ER -the nucleus -the Golgi complex

the ER

On which of the following intracellular locations does clathrin organize a coat and form vesicles? -endoplasmic network -regulated secretory vesicles -inner membrane of mitochondria -lysosomes -trans-Golgi complex

trans-Golgi complex