Cell Bio Final

The most abundant protein in the human body is. (a) Collagen (b) Myosin (c) Actin (d) Albumin

(a) Collagen

What is the pathway that allows materials or the membrane surface to move into the cell from the outside to cytoplasmic compartments?

Endocytosis

Where is the extracellular matrix most prominent?

Mammalian cells, directly attached to the plasma membrane.

Where does radiolabel first appear in the cell when a tissue is briefly incubated with radioactive amino acids?

The RER

What kind(s) of modifications are made in proteins as they move through the Golgi complex?

a) The protein's carbohydrates are modified by a series of stepwise enzymatic reactions.

You place mammary gland epithelial cells in culture and then treat them with enzymes that digest the surrounding extracellular matrix. What happens? a) The secretory and synthetic activities of the cells decrease. b) The secretory and synthetic activities of the cells increase. c) The cells die. d) The cells enunciate. e) The secretory and synthetic activities of the cells do not change.

a) The secretory and synthetic activities of the cells decrease.

What appears to be the purpose of molecular chaperones like BiP?

a) They recognize and bind to unfolded or misfolded proteins and help them attain their native structure

The activation of a membrane integrin by the binding of its cytoplasmic portion to molecules in the cytoplasm and the resultant increase in its affinity for an extracellular ligand is called ________. a) inside-out signaling b) outside-in signaling c) right-side-out signaling d) simple signaling e) integrination

a) inside-out signaling

Collagen fibrils are strengthened by covalent cross-links between ___ and ___ residues on adjacent collagen molecules. a) lysine, hydroxylysine b) proline, hydroxyproline c) lysine, hydorxyproline d) proline, hydroxylysine e) proline, lysine

a) lysine, hydroxylysine

What is the arrangement of organelles in a secretory cell from the basal end to the apical end, an arrangement that reflects the flow of secretory products from synthesis to discharge?

a) nucleus and RER - SER - Golgi complex - secretory vesicles

Type I collagen mutations cause a potentially lethal condition characterized by extremely fragile bones, thin skin and weak tendons. This condition is called _______. a) osteogenesis imperfecta b) Ehler-Danlos syndrome c) Alport syndrome d) dwarfism and skeletal deformities e) diabetes

a) osteogenesis imperfecta

The accumulation of misfolded proteins in the ER is a potentially lethal situation and thus causes the triggering of what process?

a) the unfolded protein response (UPR)

What word describes the synthesis and secretion of a substance from the cell in acontinual unregulated manner? a. constitutive b. regulated c. conditional d. constantive e. regulative

a. constitutive

How and where is the asymmetry of the phospholipid bilayers initially established?

b) It is initially established in the ER during lipid and protein synthesis.

You disaggregate cells from two different developing organs and mix them together. Initially, they form a mixed clump. What happens next? a) The clump stabilizes. b) The cells sort themselves out so that each cell adhered only to cells of the same type. c) The mixed clump persists. d) The clumped cells die. e) The clump forms a mesenchyme.

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

What would be the effect on primordial germ cells when an embryo is exposed to laminin-specific antibodies? a) They arrive at the developing gonad more quickly. b) Their movement to the developing gonad is disrupted. c) They begin to divide rapidly. d) They increase greatly in size. e) Their nuclei disintegrate.

b) Their movement to the developing gonad is disrupted.

Phospholipids are made by integral ER membrane enzymes whose active sites face the cytosol and they are inserted into the outer (cytoplasmic) leaflet of the ER membrane. How then do lipids destined for the luminal leaflet of the ER membrane get there?

b) There are enzymes called flippases that flip these lipids later into the opposite leaflet.

Enzymes can be purified from the microsomal fraction. They can then be used as antigens to make antibodies. The antibodies can then be exposed to cells and later visualized in the electron microscope. What allows them to be seen in the electron microscope?

b) attachment of gold particles to the antibodies

During gap junction formation, connexons in apposing cells become tightly connected through extensive noncovalent interactions of __________. a) connexin subunit intracellular domains b) connexin subunit extracellular domains c) connexin carbohydrates d) connexin lipids e) polynucleotides

b) connexin subunit extracellular domains

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

b) cytosolic surface of RER and free ribosomes

What could be defined as an organized network of extracellular materials found beyond the immediate vicinity of the plasma membrane? a) intracellular matrix b) extracellular matrix c) extracellular netrax d) intercellular material e) epicellular matrix

b) extracellular matrix

Basement membranes contain Type IV collagen, a nonfibrillar collagen organized in a flattened network. The Type IV collagen trimer has some interspersed nonhelical segments. What property does this confer upon basement membranes? a) strength b) flexibility c) extensibility d) transparency e) opacity

b) flexibility

What substance joins proteoglycans together into gigantic complexes called proteoglycan aggregates? These complexes can occupy very large volumes. a) hyaluronidase b) hyaluronic acid c) proteoglycase d) fibronectin e) laminin

b) hyaluronic acid

Which plant cell wall molecule is economically important as a component essential for the production of jams and jellies? a) hemicellulose b) pectin c) amylopectin d) proteins e) desmotubulin

b) pectin

What is the name for a brief incubation of a tissue with radioactivity during which labeled amino acids are incorporated into protein?

b) pulse

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?

b) the CGN

What determines the sequence of sugar addition to glycoproteins traveling through the Golgi complex?

b) the spatial arrangement of specific glycosyltransferases that contact proteins as they pass through the Golgi complex

Which model of Golgi complex formation suggests that the cisternae of a Golgi stack remain in place as stable compartments held together by a protein scaffold, while the cargo is shuttled through the Golgi via vesicles that bud from one compartment and fuse with a neighboring one? a.) the chemiosmotic model b.) the vesicular transport model c.) the secretory transport model d.) the cargo carrying model e.) the cisternal maturation model

b.) the vesicular transport model

All collagen family members consist of ______ chains arranged in a _____. a) 2, double helix b) 3, double helix c) 3, triple helix d) 3, triple lattice e) 2, triple helix

c) 3, triple helix

Each connexon in a gap junction is constructed of ___ connexin subunits. a) 2 b) 4 c) 6 d) 8 e) 10

c) 6

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

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

How does GT recognize incompletely folded or misfolded proteins that have been recently synthesized?

c) Such proteins display exposed hydrophobic residues that are absent from properly folded proteins.

What is thought to shield lysosomal membranes against attack by their enclosed enzymes?

c) carbohydrate chains attached to integral membrane proteins

In a pulse-chase procedure, if the chase is longer, which statement below correctly describes the location of the radioactively labeled proteins in the cell?

c) farther from the synthesis site

Which procedure below would lead to the visualization of the dynamic movements of specific proteins as they move through a single living cell? The proteins can be seen through the microscope eyepiece and the cells do not have to be killed for the protein to be detected.

c) fusion of the green fluorescent protein gene to the gene encoding the protein to be tracked through the cell

What kind of experiments have provided evidence that most integrins have unique functions? a) enzyme assays b) gene addition experiments c) gene knockout experiments d) freeze-fracture, freeze etch experiments e) sucrose density centrifugation

c) gene knockout experiments

What enzymes are responsible for determining the sequence of sugars added to growing oligosaccharide chains of membrane proteins or secretory proteins as they travel through the Golgi complex?

c) glycosyltransferase

What integral membrane protein family made of two membrane-spanning chains (α and β) is involved in attaching cells to their extracellular microenvironment? a) laminins b) fibronectins c) integrins d) myosins e) lysins

c) integrins

The ER reportedly contains sensors that monitor the concentration of unfolded or misfolded proteins in the lumen. One proposal suggests that the sensors are normally kept in an inactive state by ______, particularly ______.

c) molecular chaperones, BiP

A tissue has been briefly labeled with radiolabeled amino acids. It is then transferred to a medium containing unlabeled amino acids. This can be done several times with different tissue samples for varying periods of time. What is the entire procedure called?

c) pulse-chase

Vesicles that move through the Golgi complex from a trans-donor to a cis-acceptor membrane are said to move in a(n) __________ direction.

c) retrograde

What ion is not known to bind to integrins? a) calcium b) magnesium c) sodium d) divalent cations e) manganese

c) sodium

What explains the fact that plants lack the specialized junctions seen in animal cells? a) the presence of the large central vacuole b) the presence of chloroplasts c) the presence of the cell wall d) the presence of mitochondria e) the absence of centrioles, basal bodies, cilia and flagellae

c) the presence of the cell wall

When cells are homogenized, the cytomembrane system is broken into fragments, the ends of which can fuse to form small membranous spheres called ________.

c) vesicles

The degradation of the extracellular matrix, along with cell surface proteins, is accomplished mostly by a _____-containing enzyme family called _______. a) copper, matrix metalloproteinases b) copper, MMPs c) zinc, matrix metalloproteinases d) magnesium, matrix metalloproteinases e) manganese, MMPs

c) zinc, matrix metalloproteinases

How are collagen fibers in tendons arranged?

collagen fibers aligned parallel to long axis of tendon & parallel to direction of pulling force

How is the structure of the mature plant cell wall similar to the structure of the corneal stroma of the chicken embryo? a) Both contain cellulose. b) Both contain adjacent layers of fibers that run parallel to each other. c) Both contain phospholipids. d) Both contain adjacent layers of fibers that are arranged perpendicular to each other. e) Both are composed of collagen.

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

Interactions between cells and the extracellular matrix regulate _______.cell a) migration b) cell differentiation c) four dimensional organization of tissues and organs d) cell migration and cell differentiation

d) cell migration and cell differentiation

Which animal cell structure do plasmodesmata in plants most closely resemble? a) maculae adherens b) spot desmosomes c) zonulae adherens d) gap junctions e) zonulae occludens

d) gap junctions

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) ________. a) tight junction b) spot desmosome c) plasmodesma d) hemidesmosome e) gap junction

d) hemidesmosome

When tight junctions, gap junctions and desmosomes are arranged in a specific array, the assortment of surface specializations is called a(n) __________. a) junctional array b) synaptonemal complex c) belt complex d) junctional complex e) spot complex

d) junctional complex

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

d) subcellular fractionation

What lines the plasmodesmata? a) integral membrane proteins b) peripheral proteins c) carbohydrates d) the plasma membrane e) DNA

d) the plasma membrane

In the corneal stroma, the uniformity of collagen fiber size and the ordered packing of the fibers confers what property on the corneal stroma? a) strength b) flexibility c) extensibility d) transparency e) opacity

d) transparency

You place the following in a test tube containing RER-derived microsomes: mRNAs the encode a soluble protein with an N-terminal ER signal sequence, free ribosomes, and everything else needed synthesize proteins in vitro. Where are the proteins found after their production? a. Inside RER- derived vesricles if SRP is also added b. there are no proteins made c. floating free in aqueous fluid in the test tube if no srp is present d. a and c are true e. none of the above

d. a and c are true

When undifferentiated mammary gland epithelium cells that had been grown on a bare culture dish are cultured in the presence of certain extracellular molecules (e.g., laminin), what, if anything happens to them? 1) There is no change in these cells. 2) They regain their differentiated appearance. 3) They differentiate into muscle and bone cells. 4) They become organized into milk-producing, gland-like structures. a) 1 b) 2 c) 3 d) 4 e) 2 and 4

e) 2 and 4

When electron micrographs were first taken of the cell interior, what kinds of membranous structures were seen? a) membrane-bound vesicles of varying diameter, containing material of different electron density b) long channels bounded by membranes and radiating through the cytoplasm c) an interconnected network of canals d) stacks of flattened, membrane-bound sacs called cisternae e) All of the above

e) All of the above

Desmosomes are particularly numerous in tissues _____________. a) that are subjected to mechanical stress b) like cardiac muscle c) like the epithelial layers of the skin d) like the epithelial layers of the uterine cervix e) All of these are correct

e) All of these are correct

Attachment of an integrin to its ligand can induce which of the following responses within a cell? a) changes in cytoplasmic pH b) changes in cytoplasmic C2+ ion concentration c) protein phosphorylation d) gene expression e) All of these are correct.

e) All of these are correct.

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

e) Cells amassed an excess number of unfused vesicles

Which of the following is a function associated with the smooth endoplasmic reticulum in at least some cells? a) synthesis of steroid hormones b) detoxification of many organic compounds, like barbiturates and ethanol c) release of glucose into the bloodstream d) sequestration of calcium Ca2+ ions within the cisternal space e) all of the above

e) all of the above

Which of the following oligosaccharide chains is assembled exclusively in the Golgi complex? a. O-linked oligosaccharides b. N-linked oligosaccharides c. oligosaccharides attached to asparagine residues d. oligosaccharides attached to serine residues e. Both a and d are correct answers.

e. Both a and d are correct answers.

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? a.) the chemiosmotic model b.) the vesicular transport model c.) the cargo carrying model d.) the secretory transport model e.) the cisternal maturation model

e.) the cisternal maturation model

What happens to the elderly with continued cross-linking of collagen fibrils?

may lower skin elasticity & increase brittleness of bones with aging

How are proteins targeted to specific destinations within the cells? What types of signals are used by the cell to direct proteins to the right cellular location?

molecular labels (often, amino acid sequences) are used to "address" proteins for delivery to specific locations.

glycosaminoglycans function

regulate health of collagen and other things

When individual collagen molecules in a collagen fibril are arranged in a staggered manner, what happens as a result?

staggered arrangement strengthens the complex and causes the characteristic banding pattern

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

the protein content of the ER

What are the functions of basement membrane?

•Support •Binding to underlying connective tissue •Mediates signals between cells and connective tissue •Determines cell polarity •Permits flow of nutrients (permeability) •Path for cell migration •Barrier to downward growth