PCB 3134 Practice Exam 3

According to the DNA double helix model, the double helix makes one complete turn every ______ nucleotide residues

6

10

12

8

3.4

10

To which end of the microtubules are tubulin subunits primarily added in vitro?

none of the listed

the plus end

the minus end

the N-terimal end

the C-terminal end

the plus end

According to what we have learned, which of the following structures can be found in plants?

none of the others

desmosome

gap junction

tight junction

adherens junction

none of the others

An enzyme that creates transient breaks in one strand of the DNA duplex and then allows the intact, complementary strand to undergo controlled rotation, relaxing the supercoiled molecule is called a ____________

isomerase I

type I topologicase

type II topologicase

type II topoisomerase

type I topoisomerase

type I topoisomerase

What happens immediately after ATP binds to a myosin head during muscle contraction?

ATP binding induces release of the bound ADP.

ATP binding induces the detachment of the myosin head from the actin filament.

ATP binding induces cross-bridge formation with other myosin filaments

ATP binding induces the association of the myosin head with the actin filament

ATP binding induces the detachment of the myosin head from the actin filament.

Cholesterol molecules disrupt the close packing of the fatty acyl chains and interfere with their mobility. The presence of cholesterol tends to __________ and __________ fluidity.

decrease transition temperature, decreases

increase transition temperature, decreases

increase transition temperature, increases

decreases transition temperature, increases

abolish sharp transition temperature, creates a intermediate

abolish sharp transition temperature, creates a intermediate

Release of a clathrin-coated vesicle from the plasma membrane during endocytosis requires a GTP-binding protein named ____________.

AP2 adaptor

elastin

dynamin

GGA adaptor

triskelion

dynamin

DNA renaturation is the basis for many DNA analysis methods. Which of the following is not a favor influencing the rate of DNA renaturation?

the ionic strength of the solution

the concentration of DNA

the incubation temperature

the size of the interacting DNA molecules

the presence of enzymes

the presence of enzymes

During muscle contraction, the length of which region of the sarcomere stays unchanged?

I bands

none of the above

A bands

H zones

sarcomere itself

A bands

During muscle contraction, the calcium concentration in the myofibrils increases. Calcium interacts with _____________ to initiate the concentration.

tropomyosin

actin

myosin head

troponin

myosin tail

troponin

During the modification of the core oligosaccharide in the ER, two of the three terminal glucose residues are removed. The remaining glucose binds to an ER chaperone protein called __________ to help the glycoprotein to fold properly.

calnexin

glucosidase II

dolichol phosphate

hsp70

glucosidase I

calnexin

In the endocytic pathway, endocytic vesicles fuse with each other to form __________, in which the pH is lowerd to around 6.0 by _________.

early endosomes, H+-ATPases in the cytosol

early endosomes, H+-ATPases in the membrane

late endosomes, H+-ATPases in the lumen

late endosomes, H+ ATPases in the cytosol

lysosomes, H+-ATPases in the membrane

early endosomes, H+-ATPases in the membrane

Genes encoding what kinds of proteins are NOT induced during the unfolded protein response (UPR)?

ER-based molecular chaperones that can help proteins reach the native state

ER-based secretory proteins

proteins involved in the selective destruction of abnormal proteins

proteins involved in the transport of of the proteins out of the ER

proteins involved in sensing the unfolded proteins in the ER

ER-based secretory proteins

In muscle cells, how is the arrangement relative to one another of a thin and thick filaments as seen in a cross sectional electron micrograph described?

thick filaments in a hexagonal array around each thin filament

thin filaments in a hexagonal array around each thick filament

each thin filament is situated in the middle of six thick filaments

each thick filament is situated in the middle of three thin filaments

thin filaments in a heptagonal array around each thick filament

thin filaments in a hexagonal array around each thick filament

Genes that encode for ribosomal RNAs and histones are typically identical to one another and located in tandem array. The genes are located in ____________.

moderately repeated DNA sequences

satellite DNA sequences

nonrepeated DNA sequences

highly repeated DNA sequenes

microsatellite DNA sequences

moderately repeated DNA sequences

How are membranes thought to be made?

a. membranes are made de novo.

b. membranes are made as new entities from pools of proteins and lipids.

c. membranes arise from existing membranes.

d. membranes arise as newly made proteins and lipids are inserted into the ER membranes.

c and d

What part of the molecular motor dynein is responsible for traveling along the intermediate filaments?

the stalk

the stem

none of the listed

the head

the light chains

none of the listed

The wall of a microtubule is composed of globular proteins arranged in longitudinal rows, termed protofilaments. Mictrotubules consist of ___________ protofilaments aligned side by side in a circular pattern within the wall.

13

2

12

18

9

13

When a cilium or a flagellum emerges from a basal body, ________ moves building materials to the assembly site at the tip of the growing axoneme.

myosin

actin

kinesin

dynein

none of the above

kinesin

___________ move specific extracellular macromolecules in the cell interior in receptor-mediated endocytosis

clathrin-coated vesicles

COPI-coated vesicles

cell-coated vesicles

COPII-coated vesicles

carbohydrate-coated vesicles

clathrin-coated vesicles

Plasmodesmata are plant cytoplasmic channels that pass through the cell wall of adjacent cells. The plasmodesmatal pore is capable of dilation, allowing molecules up to ______________ kDa to pass between cells.

5

1

10

20

50

50

Proteins destined for peroxisomes posses a peroxisomal targeting signal (PTS). The PTS will be recognized by the PTS receptor in ________.

the cytosol

mitochondrion

rough ER

the nucleus

peroxisome

the cytosol

Proteins maintained in the lumen of the endoplasmic reticulum contain a short amino acid sequence at the C-terminus as a retrieval signal, which is ____________.

KDDL

KDEL

KKXX

KKLL

KKKL

KDEL

Cellulose is a major component of the plant cell. Cellulose is synthesized by cellulose synthase in ______________.

the cytoplasm

the extracellular space

the Golgi complex

the plasma membrane

the ER

the plasma membrane

In plants, cell-cell interactions are mediated by a structure known as ______________.

desmosome

plasmodesmata

tight junction

gap junction

focal adhesion

plasmodesmata

The distance between the plasma membrane of two cells connected by the cell-cell interaction structure desmosome is _____________.

10 nm

3 nm

30 nm

5 nm

0 nm

30 nm

Synthesis of the core portion of the N-linked oligosaccharide in the ER occurs on a lipid carrier called ____________.

mannose 6-phosphate

dolichol phosphate

glyceride

glycerol phosphate

glucose phosphate

dolichol phosphate

In the cytoplasm, vesicles travel along microtubules and microfilaments to different directions. _____________ moves from ER to Golgi along ___________.

dynein, microtubule

myosin, microfilament

kinesin, microtubule

dynein, microfilament

myosin, microtubule

dynein, microtubule

Eukaryotic cilia and flagella are hairlike, motile organelles that project from the surface of the cell. The core of the cilium and flagellum is called ___________, which contains a ____________ of microtubular structure.

gamma-tubulin ring complex, 13 protofilaments

centriole, 9 fibrils

centrosome, 9 fibrils

axoneme, 9+2 array

axoneme, 9+2 array

Transposons are able to move from one place in a chromosome to an entirely different site. The enzyme catalyzes the excision of a transposon from a donor DNA site and its subsequent insertion at a target site is called _______________, which is encoded by _______________.

topoisomerase, the host genome

transposase, the host genome

topoisomerase, the transposon

transposase, the transposon

reverse transcriptase, the transposon

transposase, the transposon

After a transposon moves from a donor DNA site to a new site using the "cute-and-paste" mechanism, it leaves a "footprint" at the donor site. The "footprint" is _____________

direct repeat in recipient DNA

inverted repeated in recipient DNA

inverted repeat in trasposon DNA

direct repeat in transposon DNA

direct repeat in recipient DNA

After an unequal chromosome crossover, a small portion of the chromosome is duplicated. Which of the following the fate of the duplicated gene.

lost through deletion

inactivated by unfavorable mutation

all of the others

the extra copy acquires a new function

both copies of the gene undergo mutations and each acquires a more specific function

all of the others

In nonmuscle motility and contractility, actin filaments work together with myosin motors. Which of the following processes does not involve actin-myosin movement?

axonal growth

cytokinesis

receptor-mediated endocytosis

phagocytosis

cell locomotion

receptor-mediated endocytosis

The plant central vacuole often occupies as much as 90% of the volume of a plant cell. Which of the following is NOT a function of central vacuoles?

generate turgor pressure to help stretch the cell wall during growth

storage of the cell's solutes and macromolecules

generate turgor to support soft tissues

regulate turnover of cell's organelles

site of intracellular digestion

regulate turnover of cell's organelles

Glycoproteins contain either N-linked or O-linked oligosaccharides. The O-linked oligosaccharides are synthesized in ________________.

the smooth ER

the cytosol

the rough ER

the Golgi complex

the Golgi complex

Which of the following structures encircles each of the cells near its apical surface to hold the cells together?

adherens junctions

gap junction

focal adehsions

desmosome

adherens junctions

Gap junctions are formed by integral membrane protein complexes called ________________, which has a channel allowing molecules smaller than ____________ kD to pass through.

connexon, 1

connexon, 50

connexins, 1

connexins, 25

connexon, 1

Cellular membranes are asymmetric. Membrane asymmetry is maintained as membrane carriers bud from one compartment and fuse to the next. Which of the following descriptions about membrane fusion between vesicles and the plasma membrane is correct?

after fusion, either surface of the vesicle can become extracellular surface of the plasma membrane.

after fusion, the internal surface of the vesicle becomes the extracellular surface of the plasma membrane.

after fusion, the cytoplasmic surface of the vesicle becomes extracellular surface of the plasma membrane.

after fusion, the internal surface of the vesicle becomes the cytoplasmic surface of the plasma membrane.

after fusion, the internal surface of the vesicle becomes the extracellular surface of the plasma membrane.

In the current version of the Golgi complex cisternal maturation model, a role of ___________ is appreciated.

TGN

transport vesicles

CGN

transport cargoes

moving cisternae

transport vesicles

There are a group of actin-binding proteins. The function of the nucleating Arp2/3 complex is ____________.

to bind to actin ATP monomers to prevent them from polymerizing

to function as a template to which the actin monomers can be added

to bind to the end of the filaments to form a cap

to bind to the side of the existing filaments and break them into two

to function as a template to which the actin monomers can be added

In the pericentriolar materials (PCM) of the centrosome, _____________ serves as the a template on which the first row of tubulin dimers assemble.

microtubule-associated protein complexes

alpha-tubulin ring complexes

alpha-and beta-tubulin complexes

beta-tubulin ring complexes

gama-tubulin ring complexes

gama-tubulin ring complexes

Kinesins are _________ motor protein.

plus end-directed microtubular

plus end-directed microfilament

mins end-directed microfilament

plus end-directed intermediate filament

minus end-directed microtubular

plus end-directed microtubular

The diameter of the intermediate filament is around ________________ nm.

15

25

10

8

20

10

Which of the following is a function performed by the cytoskeleton?

1. provides structural support that determines cell shape and resists deforming forces

2. positions various organelles within the cell interior

3. provides a network of tracks over which materials like mRNA and organelles move within cells

4. serves as a force-generating apparatus that moves cells from one place to another

2,3

1,2

1,3,4

3,4

1,2,3,4

1,2,3,4

Which region of the sarcomere represents the region of overlap between the two types of filaments in the sarcomere?

1. A bands

2. the part of the A band on either side of the H zone

3. I bands

4. Z lines

5. the part of the H zone on either side of the A band

2

Which of the following organelles does not belong to the endomembrane system?

peroxisomes

Golgi complexes

lysosomes

endosomes

vacuoles

peroxisomes

Which of the following proteins are NOT synthesized on "free" ribosomes?

proteins destined to remain in the cytosol

proteins secreted from the cell

proteins that are transported to the nucleus

proteins to be incorporated into peroxisomes, chloroplasts, and mitochondria

peripheral proteins of the inner surface of the plasma membrane

proteins secreted from the cell

Protein coat contains soluble proteins that assemble on the ___________ surface of the donor membrane at the sites where budding takes place.

epidermal

extracellular

cytosolic

none of the others

luminal

cytosolic

COPII-coated vesicles are found in between _________________.

ER and Golgi complexes

Golgi complexes and plasma membrane

Golgi complexes and lysosomes

ER and plasma membrane

Golgi complex cisternae

ER and Golgi complexes

Which of the following structures is not involved in cell-cell adhesion?

adherens junction

hemidesmosome

gap junction

plasmodesmata

tight junction

hemidesmosome

The gap between the plasma membrane of the two cells connected by adherens junction is ____________.

0 nm

10 nm

25 nm

3 nm

30 nm

30 nm

The two families of integral proteins found in the tight junctions are called _______________.

occludins and claudins

cadherins and integrins

selectins and integrins

occludins and cadherins

intergrinds and claudins

occludins and claudins

Rough endoplasmic reticulum (ER) contains a series of tubes and flattened membranous areas that are called cisternae. Each layer of cisternae is connected to neighbors by _________________.

other membranes

helicoidal ramps

smooth ER

tubes

helicoidal ramps

The dimensions of microtubules, intermediate filaments, and actin filaments are ________, ___________, and __________, respectively.

10-12 nm, 8 nm, 25 nm

30 nm, 25 nm, 10-12 nm

25 nm, 10-12 nm, 8 nm

50 nm, 25 nm, 10 nm

25 nm, 10-12 nm, 8 nm

During muscle contraction, Ca2+ is released from the sarcoplasmic reticulum into the cytosol to interact with myofibril. Ca2+ interacts with ______________ to trigger muscle contraction.

the thin filament

tropmyosin

the S1 fragment

troponin

the thick filament

troponin

Lysosomes are found in animals but not in plants. Which of the following descriptions is not correct for lysosomes?

lysosomes have similar size with diameter about 100 nm

lysosomes are the end product of endocytosis

the lysosomal membrane is protected by the carbohydrate chains of the highly glycosylated integral proteins

lysosomes contain a large number of acid hydrolases

pH in the lysosomal compartment is about 4.6

lysosomes have similar size with diameter about 100 nm

Proteasomes are hollow, cylindrical, protein degrading machines found in both the cytosol and the nucleus of cells. Proteins that are to be degraded by proteasomes are labeled by ____________.

ATP binding

phosphorylation

GTP binding

glycosylation

a polyubiquitin chain

a polyubiquitin chain

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

the mixed clumps persist

the clump stabilizes

the clump forms a mesenchyme

the clumped cells ie

the cells sort themselves out so that each cell adheres only to cells of the same type

the cells sort themselves out so that each cell adheres only to cells of the same type

Where are misfolded secretory proteins eventually destroyed?

in the Golgi complex

in the cytosol (cytoplasm)

in the RER

in the SER

in the nucleus

in the cytosol (cytoplasm)

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 be degraded

lysosome enzymes would be misfolded

lysosomal enzymes would be localized to peroxisomes

lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would be secreted

lysosomal enzymes would be localized to lysosomes

lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would be secreted