If experimentally linked α/β heterodimer integrin subunits are separated, what happens?

The molecules are unable to bind a ligand.

You are studying a plant and inject fluorescein, a fluorescent dye, into a single cell on the surface of the plant. After a brief period of time, the dye spreads to cells neighboring the injected cell. What do you conclude?

The cells are connected by plasmodesmata.

Mutations in other collagen genes can lead to a variety of distinct but related defects in collagen matrix structure, one of which causes hyperflexible joints and highly extensible skin. These defects are usually referred to as ______.

Ehler-Danlos syndromes

What changes in the central region of the dorsal surface of the single-celled epithelial layer of a chick embryo lead to the formation of the primitive nervous system?

a stoppage in the expression of E-cadherin genes and an elevation in the expression of N-cadherin genes

Why must the process by which cytochrome oxidase works be efficient?

The process deals with very dangerous substances, which, if released, could damage virtually every cell macromolecule.

What integral membrane protein family made of two membrane-spanning chains (α and β) is involved in attaching cells to their extracellular microenvironment?

integrins

What happens to the carbons of pyruvate that do not enter the Krebs cycle?

They are converted to CO₂.

The bonds that selectins form with their ligands become _______ when the interaction is __________.

stronger, placed under mechanical stress

Despite the presence of the blood-brain barrier, what cells, oddly enough, can pass through the blood-brain barrier by sending a signal that opens up the junction?

immune system cells

Which of the following is not a function of the plant cell wall?

It prevents cell-cell interactions.

Which of the following proteins are known to be associated with focal adhesions?

actin and myosin

Epidermolysis bullosa, an inherited blistering disease, is caused by ________.

genetic alterations in any one of a number of hemidesmosomal proteins

_______ are members of an integral membrane glycoprotein family that bind to specific sugar arrangements in oligosaccharides that project from the surfaces of other cells.

Selectins

You are studying a plant and inject fluorescein, a fluorescent dye, into a single cell on the surface of the plant.  After a brief period of time, the dye spreads to cells neighboring the injected cell.  What do you conclude?

The cells are connected by plasmodesmata.

The presence of Ca2+ ion transport molecules in the inner mitochondrial membrane is consistent with the mitochondrion's role in _______.

regulating cytosolic Ca2+ ion concentration

From the apical surface to the basal surface of an epithelial cell, what is the order of cell junctions observed in the junctional complex?

tight junction, belt desmosome, spot desmosomes, gap junctions

Which molecule below plays a key role in regulating the rate of glycolysis and Krebs cycle by regulating the activity of key enzymes?

ATP

Which of the following tissues are typically derived from mesenchymal cells?

mesodermal tissues, blood and muscle

Attachment of an integrin to its ligand can induce which of the following responses within a cell?

All of these are correct.

Why do cells flatten out as they make contact with a surface?

They send out projections that make increasingly stable attachments.

Cells were allowed to bind to beads that had been covered with a coating of fibronectin. When the membrane-bound beads were pulled by an optical tweezer, the resultant mechanical stimulus was transmitted into the cell interior. What response did this cause?

It generated a wave of Src kinase activity.

Mutations in other collagen genes can lead to a variety of distinct but related defects in collagen matrix structure, one of which causes hyperflexible joints and highly extensible skin. These defects are usually referred to as ______.

Ehler-Danlos syndromes

Lymphocytes are isolated and labeled with radioactive isotopes. They are then exposed to frozen tissue sections of a lymphoid organ. What happens?

The lymphocytes selectively adhere to the endothelial lining of venules in peripheral lymph nodes.

You are investigating the interactions of integrin α and β
subunits and isolate the extracellular portion of an integrin as a soluble α/β
heterodimer. The heterodimer lacks the associated transmembrane and cytoplasmic domains normally present as part of the molecule. You experimentally link the α and β subunits at the bases of their legs so that the ligand-binding regions of the α and β subunits approach one another. Which of the following statements is true about the molecules formed?

The molecules bind their ligand tightly.

What could be defined as an organized network of extracellular materials found beyond the immediate vicinity of the plasma membrane?

extracellular matrix

What is formed when electrons reach the bottom of the mitochondrial electron transport chain and bind to the final electron acceptor?

water

What energy source other than ATP hydrolysis do mitochondria, unlike most other organelles, routinely use to power their activities?

proton-motive force

Patients that have died of L1-deficiency disease are missing a nerve tract that ________.

runs between the brain and the spinal cord and runs between the two halves of the brain

You genetically engineer nonadhesive cells to express one variety of cadherins and then mix the cells in various combinations. You then monitor their interactions. What do you observe?

The genetically engineered cells adhered preferentially to cells expressing the same cadherins.

What changes in the central region of the dorsal surface of the single-celled epithelial layer of a chick embryo lead to the formation of the primitive nervous system?

a stoppage in the expression of E-cadherin genes and an elevation in the expression of N-cadherin genes

How is the structure of the mature plant cell wall similar to the structure of the corneal stroma of the chicken embryo?

Both contain adjacent layers of fibers that are arranged perpendicular to each other.

What is responsible for recognizing lysosomal enzymes and localizing them to the lysosomes?

mannose 6-phosphate receptors (MPRs)

The _______ binds integral proteins of the inner mitochondrial membrane and inserts them into lipid bilayer and the ______ binds matrix proteins and translocates them completely through the inner mitochondrial membrane into the aqueous matrix compartment.

TIM22 complex, TIM23 complex

What accounts for the differences in function between the types of ER?

the protein content of the ER

To what site does Sar1 bind after it binds to GTP?

the cytosolic leaflet of the ER bilayer

Which of the following is a difference between the coats of COPII- and clathrin-coated vesicles?

The outer scaffold subunits of the clathrin lattice of coated vesicles overlap extensively, while those of the COPII lattice of coated vesicles do not overlap.

What effect does the binding of the SRP to the growing polypeptide chain and the ribosome have on protein synthesis?

Protein synthesis ceases temporarily.

Typically, receptors for hormones or growth factors are destroyed during endocytosis, leading to a reduction in the cell's sensitivity to further stimulation by that particular hormone or growth factor. This is a mechanism by which cells regulate their ability to respond to extracellular messengers. What is it called?

receptor down-regulation

What would happen if the enzyme that adds phosphate groups to the appropriate mannose residues on the carbohydrate chains of lysosomal enzymes were defective?

Lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would eventually be secreted.

Which of the following organelles imports proteins through one or more outer boundary membranes?

All of these are correct.

- mitochondria

- nucleus

- peroxisomes

- chloroplasts

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

Which enzyme of the Krebs (TCA) cycle is different from the others with respect to its location and where is it located?

succinate dehydrogenase, inner mitochondrial membrane

Based on you knowledge of the origin, structure, and functions of the membranes and matrix of the mitochondrion, the balance between fusion and fission is likely a major determinant of __________.

number, length and degree of interconnection

Evidence strongly suggests that the bent conformation of an integrin is _______ and unable to bind its ligand.

inactive

What proteins have been shown to be altered by genetic mutations in patients who suffer from epidermolysis bullosa?

All of these are correct.

What is the function of most IgSFs?

mediating specific interactions of lymphocytes with cells needed for the immune response

Which molecule below plays a key role in regulating respiratory rate in the mitochondrion?

ADP

What properties do mitochondria share with peroxisomes?

All of these are correct.

It has been shown that one part of ATP synthase rotates relative to another part of the enzyme. This phenomenon is referred to as ________.

rotational catalysis

An unusual type of phospholipid is found in the myelin sheath that insulates brain axons; abnormalities in the synthesis of this phospholipid can lead to severe neurological dysfunction. What are these phospholipids called?

plasmalogens

Which plant cell wall molecule is economically important as a component essential for the production of jams and jellies?

pectin

What enzyme transfers a block of sugars to asparagine residues of a polypeptide as it enters the RER?

oligosaccharyltransferase

How do protein coats select the cargo molecules to be carried by the vesicles they help to form?

The protein coats have a specific affinity for the cytosolic tails of integral membrane proteins that reside in the donor membrane.

The oligosaccharide block that is added to secretory proteins after they enter the ER lumen goes through a number of modifications after its attachment. What is the first modification that occurs?

trimming of some sugars from the oligosaccharide block

What happens to the breakdown products of bacteria brought into mammalian phagocytic cells (like macrophages and neutrophils) from the extracellular environment?

Peptides produced during digestion are posted on the phagocytic cell's surface.

Where are misfolded secretory proteins eventually destroyed?

in the cytosol (cytoplasm)

What would happen to the movement of vesicles toward their eventual target if a microtubule inhibitor like colchicine were added to the cells?

Vesicle movement would slow or stop.

The vesicle containing material taken into the cell by phagocytosis is called a(n) _________.

phagosome

Which of the following strategies is used by Mycobacterium tuberculosis, the bacterium responsible for tuberculosis, to avoid being destroyed by phagocytosis?

The bacterium inhibits fusion of the phagosome with a lysosome.

The two separate (basic) categories of uptake of extracellular materials into cytoplasmic vesicles are ______ and ______.

phagocytosis, endocytosis

Cells are infected with a vesicular stomatitis virus (VSV) strain in which a viral gene (VSVG) is fused to the green fluorescent protein gene. When the chimeric protein is synthesized, what pathway does it follow from synthesis until it leaves the cell?

RER, Golgi complex, plasma membrane, viral envelopes

Mutations in other collagen genes can lead to a variety of distinct but related defects in collagen matrix structure, one of which causes hyperflexible joints and highly extensible skin. These defects are usually referred to as ______.

Ehler-Danlos syndromes

The cells of the epiblast of a developing mammalian embryo display what cell adhesion molecules on their surfaces, molecules that presumably promote their close association with one another?

E-cadherins

The tightest attachment between a cell and its extracellular matrix is seen at the site where an epithelial cell is attached to the underlying basement membrane. The specialized adhesive structure found at such a site is called a(n) ________.

hemidesmosome

Which tissues below are not typically derived from the single-celled epithelium on the dorsal surface of a chick embryo after gastrulation?

muscle

Peroxisomal enzymes __________.

produce hydrogen peroxide, break down hydrogen peroxide and include catalase

The dense central structure that is derived from the smooth endoplasmic reticulum and usually seen in the plasmodesmata is called a(n) ________.

desmotubule

The direct formation of ATP by the transfer of a phosphate group from a donor molecule to ADP is called ________.

substrate-level phosphorylation

You disaggregate cells from two different developing organs and mix them together. Initially, they form a mixed clump. What happens next?

The cells sort themselves out so that each cell adhered only to cells of the same type.

The oligosaccharide block that is added to secretory proteins after they enter the ER lumen goes through a number of modifications after its attachment. What is the first modification that occurs?

trimming of some sugars from the oligosaccharide block

Which molecule below is a GTP-binding protein that is required for the release of a clathrin-coated vesicle from the membrane on which it was formed?

dynamin

How are integral membrane proteins thought to enter the lipid bilayer?

The aqueous translocon channel seems to have a gate that continuously opens and closes, giving each nascent polypeptide segment a chance to partition itself into the lipid bilayer's hydrophobic core.

What kind of molecule has been implicated in preparing polypeptides for mitochondrial uptake, including those that specifically direct mitochondrial proteins to the cytosolic surface of the outer mitochondrial membrane?

molecular chaperones

To what residue of a polypeptide are N-linked oligosaccharide chains attached as that poypeptide enters the RER lumen through the translocon?

asparagine

Lipid species like the phosphoinositides can have a dynamic regulatory role because _______.

All of these are correct.

The outer and inner chloroplast membranes contain distinct translocation complexes named ________, respectively, that work together during protein import.

Toc and Tic complexes

What molecules do the AP2 adaptors of the clathrin coat connect?

the clathrin molecules and cargo molecules

Which list below names the compartments into which chloroplast proteins must be imported?

inner and outer chloroplast membranes, the intermembrane space, the stroma, thylakoid membranes, thylakoid lumen

What is it about lysosomes that initially deactivates most ingested bacteria?

low pH

What powers the movement of proteins into the mitochondrial matrix?

electric potential across the inner mitochondrial membrane acting on the positively-charged targeting signal

What always serves as the donor of a sugar to the growing oligosaccharide chain of a glycoprotein?

a nucleotide sugar

Once an organelle to be destroyed, like a mitochondrion, has been surrounded with a double membrane, what is the name of the structure that has been produced?

autophagosome

Most vesicles budding from the Golgi body have a fuzzy, electron-dense coat on their ______ surface. The coat appears to be made of _______.

cytosolic, protein

What protein is associated with HDL particles?

apolipoprotein A-1

Which of the following are enzymes that are involved in detoxification of organic compounds in the SER of liver cells?

oxygen-transferring enzymes, oxygenases and members of the cytochrome P450 family

The best-studied adaptors that participate in the formation of the coated pits and coated vesicles of clathrin-mediated endocytosis are the _____ adaptors.

AP2

What happens to yeast cells that cannot transport proteins into the ER lumen cotranslationally?

They survive, but grow more slowly than normal yeast cells.

What happens to the breakdown products of materials brought into many single-celled organisms from the extracellular environment?

They are used as nutrients and are released into the cytoplasm.

What allows the interface between the Sec13-Sec31 subunits to form cages of varying diameter, thus accommodating vesicles of varying size?

a degree of flexibility built into the interface between the Sec13-Sec31 subunits

What does the conformation-sensing enzyme UGGT do if it binds to a misfolded or incompletely folded glycoprotein?

It adds a single glucose back to one of the mannose residues at the exposed end of the recently trimmed oligosaccharide.

The separation of organelles or vesicles derived from different organelles is called ______.

subcellular fractionation

Where in the Golgi complex does most protein sorting occur?

the TGN

How many subcompartments do peroxisomes have into which an imported protein can be placed?

2

What is the effect on a yeast cell of the presence of a mutant gene involved in vesicle fusion?

Cells amassed an excess number of unfused vesicles.

What removes the stroma-targeting domain and where does the removal occur?

a processing peptidase, stroma

How many subcompartments are there in chloroplasts into which proteins can be delivered?

6

What are the two sites within a cell at which protein synthesis is generally thought to occur?

cytosolic surface of RER and free ribosomes

What types of molecules below can a cell internalize by receptor-mediated endocytosis?

All of these are correct

Which part of the Golgi complex is thought to function primarily as a sorting station that distinguishes between proteins to be shipped back to the ER and those that are allowed to proceed to the next Golgi station?

the cis-Golgi network (CGN)

You incubate liposomes with a series of purified proteins normally found in the coats of cell transport vesicles. After adding one of them to the liposome mixture, budding of vesicles from the liposomes began. What does this mean?

The protein is involved in the initiation of vesicle formation

Which of the following organelles imports proteins in their native, folded conformation?

peroxisomes

Which protein(s) below is(are) recruited to the COPII coat by Sar1-GTP?

both Sec23 peripheral proteins of the inner surface of the plasma membrane and Sec24