Chapter 8 Practice Quiz

Which structure is NOT part of the endomembrane system? Nuclear envelope Chloroplast Golgi apparatus Endoplasmic reticulum

Chloroplast

Typically, a Golgi stack contains fewer than ________ cisternae. 100 60 20 8 4

8

Extracellular vesicles have been shown to carry messages between cells through the delivery of _________ to the recipient cell. mRNAs microRNAs and noncoding RNAs cytoplasmic proteins membrane proteins All of the answers are correct.

All of the answers are correct.

A coated pit: is a specialized region of the plasma membrane where RME occurs. is covered on its cytoplasmic face by electron-dense molecules including clathrin. invaginates to form clathrin-coated vesicles. contains a high concentration of receptors for a specific ligand. All of the choices are correct.

All of the choices are correct.

The unfolded protein response (UPR): occurs when there are too many misfolded proteins in the ER. is inhibited by BiP molecules. involves the synthesis of more chaperones in the ER. inhibits enzymes involved in protein synthesis. All of the statements are true.

All of the statements are true.

Which of the following statements about clathrin is true? It binds to the adaptor AP2. It is arranged as a triskelion. It is found in the structure of coated pits. All of these are correct.

All of these are correct.

Contrary to COPII-coated vesicles, COPI-coated vesicles:1) are implicated in anterograde movement of proteins.2) are implicated in retrograde movement of proteins.3) contain GTP-binding proteins. 3 1 Both 2 and 3 are correct 2

Both 2 and 3 are correct

Which one of the following statements is TRUE? COPI-coated vesicles transport materials from the ER to the Golgi complex. COPI-coated vesicles transport materials from the cis Golgi cisternae to the trans Golgi cisternae. COPII-coated vesicles transport materials in a retrograde direction. Spectrin-coated vesicles are involved in the endocytic pathway. COPI-coated vesicles transport materials in a retrograde direction from the Golgi towards the ER.

COPI-coated vesicles transport materials in a retrograde direction from the Golgi towards the ER.

Which coated vesicles move materials in an anterograde direction from the ER toward the ERGIC and Golgi stack? COPII-coated vesicles COPI-coated vesicles clathrin-coated vesicles cadmium-coated vesicles both COPII-coated vesicles and COPI-coated vesicles

COPII-coated vesicles

What is the effect on a yeast cell of the presence of a mutant gene involved in vesicle fusion? The ER shrank. The nucleus became swollen. The Golgi complex expanded greatly. Cells accumulated expanded ER cisternae. Cells amassed an excess number of unfused vesicles.

Cells amassed an excess number of unfused vesicles.

A researcher used a radioactive label to track the pathway of an enzyme secreted by pancreatic cells. What is the most likely pathway? Golgi → ER → lysosome ER → Golgi → vesicles that fuse with plasma membrane Golgi → ER → vesicles that fuse with plasma membrane ER → Golgi → lysosome

ER → Golgi → vesicles that fuse with plasma membrane

Membrane vesicles, with their enclosed cargo, bud from the edges of the ER and travel to the: Golgi complex. plasma membrane. nuclear membrane. secretory vesicles. vacuole.

Golgi complex.

Which one of the following is a FALSE statement about secretory pathways? Materials produced in the endoplasmic reticulum may leave the cell by phagocytosis. During constitutive secretion, materials are continually secreted from the cell. Regulated secretion occurs only in response to an appropriate stimulus. Materials produced in the Golgi complex may move to the plasma membrane, to a lysosome, or to the large, central vacuole of a plant cell. Constitutive secretion contributes to the formation of the plasma membrane.

Materials produced in the endoplasmic reticulum may leave the cell by phagocytosis.

What is the function of SNARE proteins? Synthesis of clathrin Responsible for glycosylation Mediates targeting proteins, membranes and organelles All of these choices are functions of clathrin

Mediates targeting proteins, membranes and organelles

Which one of the following statements is FALSE about coated vesicles? Protein coats act as mechanical devices that cause the membrane to curve and form a budding vesicle. The protein coat is formed from soluble proteins that assemble on the cytosolic surface of the donor membrane at sites where budding takes place. Protein coats include the machinery required to target and dock the vesicle to the correct acceptor membrane. Protein coats provide a mechanism for selecting the materials carried by the vesicle. Protein coats surround the nucleus of the cell.

Protein coats surround the nucleus of the cell.

What effect does the binding of the SRP to the growing polypeptide chain and the ribosome have on protein synthesis? Protein synthesis accelerates. Protein synthesis ceases temporarily. Protein synthesis ceases permanently. Protein synthesis is terminated. The ribosome dissociates.

Protein synthesis ceases temporarily.

A drug that inhibits dynamin was added to cells. Which of the following events would be affected by the drug? Release of Clathrin coated vesicles Regulation of phosphoinositides Formation of GTP-binding proteins None of these is correct

Release of Clathrin coated vesicles

An investigator can visualize biochemical processes within a cell by determining the location of radioactively labeled materials by this process: autoradiography. homogenization. tags of green fluorescent protein. subcellular fractionation. microsomal reconstitution.

autoradiography.

Which of the following statements is a TRUE description of events at the presynaptic membrane? SNARE proteins on the synaptic vesicle include syntaxin and SNAP-25. The toxins that cause botulism and tetanus target SNARE proteins and prevent the release of neurotransmitter molecules. Fusion between the vesicle and the presynaptic membrane is inhibited by high levels of calcium. Synaptobrevin is found on the presynaptic nerve cell membrane before synaptic vesicle fusion. SNARE molecules from apposing membranes form four-stranded bundles that are sufficient for membrane fusion.

The toxins that cause botulism and tetanus target SNARE proteins and prevent the release of neurotransmitter molecules.

Cytoplasmic membrane systems are characteristic of _________cells? embryonic prokaryotic eukaryotic plant

eukaryotic

Based on what is known about the involvement of calcium ions in exocytosis, what should happen if Ca2+ ions are injected into a cell? Secretion stops. Wholesale exocytosis of secretory product occurs. Wholesale endocytosis of secretory product occurs Wholesale exocytosis of nuclear contents occurs. Endocytosis rates are accelerated.

Wholesale exocytosis of secretory product occurs.

Misfolded proteins: will attain their normal three-dimensional structure after they are secreted from the cell. are destroyed. lack hydrophobic residues. are sequestered within membrane-bound vesicles. are surrounded by oligosaccharides.

are destroyed.

Molecular chaperones in the rough ER: move newly synthesized proteins into vesicles. bind to misfolded proteins and help them to fold into their correct three-dimensional structure. increase the formation of disulfide bonds. act with G proteins as molecular switches. produce a signal recognition protein (SRP).

bind to misfolded proteins and help them to fold into their correct three-dimensional structure.

Proteasomes: synthesize proteins that are folded within the ER. break down misfolded proteins. engulf proteins and bring them into the cell from the external environment. trigger the unfolded protein response (UPR). trigger cell death.

break down misfolded proteins.

A major advantage of using green fluorescent protein rather than autoradiography is that the process: uses viruses. can be performed at low temperatures. requires an electron microscope. can be used in living cells. can track movement of materials within a cell.

can be used in living cells.

Studies of cell physiology that occur in test tubes that do not contain whole cells are called ______. in vivo systems cell-free systems test tube systems online systems cellonic systems

cell-free systems

Receptor-mediated endocytosis is characterized by the use of: t-SNAREs peroxisomes coated pits v-SNAREs

coated pits

A protein is transported in a secretory vesicle and discharges into the extracellular space in a continuous fashion. What type of secretion is this? regulated biosynthetic constitutive unregulated

constitutive

Glycosylation: adds random monosaccharides to an oligosaccharide chain. is accomplished by enzymes associated with free ribosomes. depends on the spatial localization of particular enzymes when adding monosaccharides to the oligosaccharide chains of a glycoprotein. may be abnormal, but health-related effects are never seen. is a rare event in the RER.

depends on the spatial localization of particular enzymes when adding monosaccharides to the oligosaccharide chains of a glycoprotein.

Which of the following processes does NOT take place in the Golgi complex? glycosylation of glycoproteins and glycolipids digestion of misfolded proteins processing of membrane proteins processing of lysosomal proteins

digestion of misfolded proteins

Functions of the smooth endoplasmic reticulum includes all of the following functions EXCEPT: storing ions, such as calcium. synthesizing steroid hormones. detoxifying drugs. oxidizing hydrophobic compounds into hydrophilic compounds. directing proteins to their chosen cellular locations.

directing proteins to their chosen cellular locations.

SNARE proteins are primarily involved in: movement of vesicles. tethering vesicles to a target compartment. docking vesicles to a target compartment. fusion of membranes. release of the contents from vesicles.

docking vesicles to a target compartment.

Which of the following enzymes are typically found in lysosomes? hydrolytic enzymes (acid hydrolases) oxidoreductases transferases lyases ligases

hydrolytic enzymes (acid hydrolases)

Exocytosis: involves fusion of a secretory vesicle with the plasma membrane. serves to move material from the outside of the cell to the inside of the cell. is the mechanism that takes up neurotransmitters from the synaptic cleft. can be affected by sodium levels in the cell. is characterized by pinocytosis.

involves fusion of a secretory vesicle with the plasma membrane.

Pinocytosis: is also known as bulk-phase endocytosis. involves clathrin receptors on coated vesicles. is used for the ingestion of particulate matter. results from the ingestion of specific ligands that bind to the cell surface. occurs in specialized regions of the plasma membrane called coated pits.

is also known as bulk-phase endocytosis.

Lysosomal enzymes are sorted to enter lysosomes from the TGN because they contain: clathrins. mannose 6-phosphate. MPRs. Arf1. GGA adaptors.

mannose 6-phosphate.

The endomembrane system when homogenized is broken up into vesicles, which are heterogeneous but similar in size. These vesicles can be purified and, after purification, often retain their biological activity. They are collectively referred to as _________. endosomes microsomes ribosomes minisomes lysosomes

microsomes

Vesicle-tubular carriers (VTCs) move along tracks composed of: microfilaments. smooth endoplasmic reticulum. secretory vesicles. the endomembrane system. microtubules.

microtubules.

Organelles of the endomembrane system include all of the following EXCEPT: endoplasmic reticulum. lysosomes. mitochondria. endosomes. Golgi complex.

mitochondria.

Flippases: convert rough ER into smooth ER. move newly synthesized materials from the Golgi complex into the cytoplasm. are important in the exocytosis of secreted materials. produce a new membrane bilayer in the Golgi complex. move newly synthesized phospholipids from the half of the bilayer facing the cytosol into the opposite leaflet of the membrane bilayer.

move newly synthesized phospholipids from the half of the bilayer facing the cytosol into the opposite leaflet of the membrane bilayer.

Autoradiography is useful to study endomembranes because: incubation is not required. it is easy to photograph the cells. one can follow all of the steps in the process of secretion. all of these are correct.

one can follow all of the steps in the process of secretion.

As a result of exocytosis, the luminal surface of the vesicle becomes: part of the inner surface of the plasma membrane. the cytosolic surface of the vesicle. part of the cytosolic surface of the synaptic cleft. part of the outer surface of the plasma membrane. the fate of the luminal surface of the vesicle differs in different cells.

part of the outer surface of the plasma membrane.

The two separate (basic) categories of uptake of extracellular materials into cytoplasmic vesicles are ______ and ______. phagocytosis, exocytosis pinocytosis, exocytosis phagocytosis, endocytosis pinocytosis, endocytosis exocytosis, endocytosis

phagocytosis, endocytosis

A pulse-chase experiment allows researchers to determine: what organelles are active within a cell. what materials the cell is synthesizing in the endoplasmic reticulum. the movements of newly-synthesized materials within the cell. what materials are being secreted by the cell. what materials are being stored in the cell.

the movements of newly-synthesized materials within the cell.

Polypeptides synthesized on "free" ribosomes do NOT include: enzymes used in glycolysis. proteins that are used in the nucleus. peripheral proteins attached to the cytosolic surface of the plasma membrane. cytoskeletal proteins. plasma membrane receptors with transmembrane domains.

plasma membrane receptors with transmembrane domains.

The Binding Immunoglobin Protein (BiP) is a molecular chaperone that is essential for the translocation of secreted peptides into the lumen of the ER. Because it is a chaperone, it is important for _________________________. recognition of the signal sequence. protein folding. t-RNA charging. none of these choices.

protein folding.

The smooth endoplasmic reticulum is responsible for all of the following EXCEPT: protein modifications. sequestering calcium ions. synthesis of steroid hormones. detoxification in the liver.

protein modifications.

Where is N-linked protein glycosylation initiated? rough ER smooth ER lysosomes Golgi apparatus cytoplasm

rough ER

A signal sequence is found at the N-terminus of: secretory proteins. all proteins. housekeeping proteins. none of these is correct.

secretory proteins.

The signal sequence is typically found on _________ of a peptide designated to be inserted into the lumen of the rough endoplasmic reticulum (RER). the amino-terminus the carboxy-terminus an internal portion none of these choices

the amino-terminus

Which of the models below suggests that the Golgi cisternae are transient structures that form at the cis face of the stack by fusion of membranous carriers from the ER and ERGIC and that each cisterna travels through the Golgi complex from the cis to the trans end of the stack, changing in composition as it progresses? the cisternal maturation model the cargo carrying model the vesicular transport model the secretory transport model the chemiosmotic model

the cisternal maturation model

The three-legged assembly of protein chains that makes up a clathrin molecule and that can assemble into a network of polygons resembling a honeycomb is called a(n) _____. trigeminy triskeleton trigellium triskelion triskellium

triskelion

Coated vesicles may be covered by all of the following EXCEPT: COPII COPI clathrin ubiquitin

ubiquitin