Cell Chapter 17 Cytoskeleton and chapter 11 membranes

Microtubules extend from organizing centers in the cell. Which is an example of an organizing center? a. basal body of a cilium b. nuclear periphery c. centromere of a chromosome d. vesicle membrane

Basal body

Taxol and colchicine are used to treat cancer because they arrest dividing cells in mitosis. What is the mechanism of action of these drugs? a. Both drugs stabilize microtubules. b. Both drugs destabilize microtubules. c. Both drugs constrain the dynamic instability of microtubules. d. Taxol prevents polymerization of microtubules, colchicine prevents disassembly of microtubules.

Both drugs constrain the dynamic instability of microtubules

When an action potential excites a muscle cell, where do the calcium ions come from? a. the sarcoplasmic reticulum b. the extracellular space c. the calcium secretory vesicles d. both the extracellular space and the sarcoplasmic reticulum

Both the extracellular space and the sarcoplasmic reticulum

If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane? a. Vesicles cannot fuse with the plasma membrane. b. the cytosolic face of the bilayer c. randomly on one side or another d. the extracellular face the bilayer

Bwhat

If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer? a. because the membrane bends in such a way that the polar heads of the lipids contact the transmembrane helix b. because many transmembrane alpha helices must come together in a way that neutralizes the hydrophilic backbone c. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer d. because the hydrophilic backbone makes a hole in the membrane

C

Which motor protein is an ATPase, has two globular heads, moves toward the (-) end of a microtubule, and generally interacts with cargo via an adaptor protein? a. myosin-I b. kinesin c. myosin-II d. cytoplasmic dynein

Cytoplasmic dynein

A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)? a. short, saturated fatty acid tails b. long, unsaturated fatty acid tails c. long, saturated fatty acid tails d. short, unsaturated fatty acid tails

Long sat.

Plasma membrane proteins that move ions in and out of cells using active transport are called a. channels. b. transporters. c. receptors. d. anchors.

Transporters

A less permeable membrane is likely to have a. less cholesterol. b. shorter fatty acid tails. c. more cholesterol. d. many unsaturated fatty acids.

More cholesterol

A ___________ is a long structure found in abundance in the cytoplasm of a single skeletal muscle fiber, and is composed of many bundles of actin and myosin filaments that are arranged in repeating units. a. thick filament b. myofibril c. sarcomere d. contractile ring

Myofibril

Which of the following motor proteins has one head domain, moves along actin toward the plus end, and is found in all cell types? a. myosin-II b. cytoplasmic dynein c. kinesin d. myosin-I

Myosin-I

The end of the microtubule that has /alpha-tubulin exposed is the a. (+) end. b. Neither end has /alpha-tubulin exposed. c. (-) end. d. Both (+) and (-) ends.

(-) end

________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass. a. Proteins, lipids b. Lipids, carbohydrates c. Lipids, proteins d. Carbohydrates, lipids

A Plasma membrane proteins that move ions in and out of cells using active transport are called a. channels. b. transporters. c. receptors. d. anchors.

Detergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane. a. amphipathic b. hydrophobic c. hydrophilic d. polar

AaaaA

In a famous experiment, mouse cells and human cells were fused into hybrid cells and the membrane proteins of human origin and mouse origin were specifically tagged and examined. After cell fusion and incubation, what was observed by investigators? a. The mouse and human proteins mixed evenly throughout the membrane of the hybrid cell. b. The human proteins mixed throughout the membrane of the hybrid cell, whereas the mouse proteins remained in half of the membrane, in their original location. c. The mouse and human proteins remained separated from each other on opposite sides of the hybrid cell. d. The mouse proteins mixed throughout the membrane of the hybrid cell, whereas the human proteins remained in half of the membrane, in their original location.

Aaaaaaaaaasaaaa

At the leading edge of a cell, ARP proteins help form new branches on actin filaments to push the leading edge forward using the force of the polymerization, as shown in the figure below. ECB5_CP_1703 Click to view larger image. a. at the plus ends of newly polymerized actin filaments b. in branches off of existing actin filaments c. at the minus ends of depolymerizing actin filaments d. from the capped ends of actin filaments

At the plus ends of newly polymerized actin filaments

Which of the following is a common transmembrane protein structure that can traverse the membrane to form a pore or channel by alternating hydrophobic and hydrophilic amino acids? a. single-pass alpha helix b. multipass alpha helix c. beta barrel d. beta sheet

BDetergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane. a. amphipathic b. hydrophobic c. hydrophilic d. polar

How is muscle contraction reversed? a. Calcium ion pumps in the sarcoplasmic reticulum reduce the cytosolic calcium levels and tropomyosin blocks the myosin binding site on actin. b. Calcium is pumped out of the cell to reverse the voltage and cause myosin to degrade. c. Calcium is neutralized by an influx of negatively charged ions, which block calcium from binding to myosin. d. Calcium binds to calmodulin and is quickly degraded to relieve calcium's inhibition of tropomyosin.

Calcium ion pumps in the sarcoplasmic reticulum reduce the cytosolic calcium levels and tropomyosin blocks the myosin binding site on actin

How do calcium ions stimulate contraction in nonmuscle cells and smooth muscle cells? a. Calcium ions lead to activation of a kinase that phosphorylates nonmuscle myosin to alter its conformation and enable actin binding. b. Calcium ions bind to troponin and lead to a conformational change in tropomyosin that exposes the myosin binding sites on the actin filament. c. Calcium ions released into the cell promote the release of secretory vesicles that send neurotransmitters to neighboring cells to stimulate an action potential. d. Calcium ions trigger an action potential in the cell, leading to gene expression changes that influence contraction.

Calcium ions bind to troponin and lead to a conformational change in tropomyosin that exposes the myosin binding sites on the actin filament.

Why do cells regulate their membrane fluidity? a. so they don't freeze in cold temperatures b. so that large, charged molecules can easily pass through the membrane c. to keep two neighboring cells from easily fusing d. to allow membrane proteins to diffuse to where they are needed for their function

D

Where are new phospholipids made? a. nucleus b. Golgi apparatus c. mitochondria d. endoplasmic reticulum

Er

Which type of movement is the least common for lipids in a bilayer? ECB5_CP_1102 Click to view larger image. a. flip-flop b. lateral diffusion c. flexion d. rotation

Flip flop

Phospholipids assemble into in a membrane using a. assembly proteins. b. covalent bonds. c. enzymes. d. hydrophobic forces.

Hydrophobic forces

Which of the cytoskeletal structures are made up of protein subunits that are fibrous? a. actin filaments b. microtubules c. None. All of the protein subunits that make up cytoskeletal structures are globular. d. intermediate filaments

Intermediate filaments

In terms of structure, if cytoplasmic intermediate filaments are described as ropes, nuclear lamins could be best described as a. mesh. b. string. c. glass. d. wood.

Mesh

Microtubules participate in the spatial polarization of nerve cells because a. microtubules are only located in the nerve cell body. b. microtubules extend through the axon with (-) ends toward the terminal and bind vesicles there. c. microtubules have no polarity. d. microtubule (-) ends originate near the cell body allowing (+) end-directed transport along the axon.

Microtubules (-) ends originate near the cell body allowing (+) end-directed transport along the axon

Which of these macromolecules is NOT commonly found in the plasma membrane? a. nucleic acids b. fatty acids c. proteins d. carbohydrates

Nucleic acids

Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins. a. peripheral membrane b. lipid-linked c. integral membrane d. monolayer-associated

Peripheral

Microtubules are made up of 13 ___________ that are linear chains of ___________. a. microfilaments; tubulin rings b. tubulin dimers; protofilaments c. tubulin rings; microfilaments d. protofilaments; tubulin dimers

Protofilaments and tubulin dimers

Which of the following is an important function of intermediate filaments? a. providing tensile strength to the cell and the nucleus b. forming attachments for cells to move along a substrate c. moving vesicles from location to location in the cell d. separating chromosomes during mitosis

Providing tensile strength to the cell and the nucleus

The binding of ATP causes a conformational change in myosin that a. releases the myosin head from the actin filament. b. moves the myosin head one step forward on the actin filament. c. move the actin filament in a force-generating "power stroke." d. attaches the myosin head to the actin filament.

Releases the myosin head from the actin filament

A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane? a. glycolipids b. Golgi apparatus c. flippase d. scramblase

Scramblase

Microtubules are inherently unstable unless they are a. able to bind GTP. b. bound to kinesin. c. assembled in the nucleus. d. stabilized by a (+) end attachment.

Stabilized by a (+) end attachment

How do the intermediate filament proteins keratin, vimentin, and neurofilaments differ from each other? a. The dimers assemble into filaments in a completely different way. b. They are different at the head and tail domains that are exposed at the surface. c. They do not differ. All intermediate filament proteins are identical. d. Their central rod domains are very different and do not all form coiled-coils.

They are different at the head and tail domains that are exposed at the surface

Which of the following actin-binding proteins prevent polymerization of actin monomers? a. formins and profilin b. thymosin and ARPs c. formins and ARPs d. thymosin and profilin

Thymosin and profilin