Cell and Molec Chap 12, Cell Bio Ch 12, Cell Bio Chapter 17, exam 3
3. drag the rest of the cell forward by traction
*The cell using this anchor to drag the rest of the cell body forward via contraction *Myosin motor proteins aid in the contraction
step 1 push out the protruding leading edge of the cell
*driven by actin polymerization *leading edge now called a lamellipodia
T or F a transporter can only mediate passive/facilitated diffusion
false
What characteristic can a molecule pass through easily without help?
fay soluble small nonpolar uncharged polar: small -use simple diffusion
Describe the polarity structure of the actin filament?
filament has structural polarity with minus ends and plus ends
what is the actin filament made of?
filament is a twisted chain of actin monomers
Intermediate filaments help protect animal cells from mechanical stress because ____________. Answers: A. filaments make up the desmosome junctions that connect cells; these junctions are more important than the internal network of filaments for protecting cells against mechanical stress. B. filaments remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. C. filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. D. filaments directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next, helping to distribute locally applied forces.
filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells.
what are the purpose of microtubules? examples?
for cellular cytoplasmic organization ------ -anchor membrane bound organelles -create a track for vesicles movement between membrane
channels
form tiny hydrophilic pores which solutes pass through diffusion
When does the formation of microtubules began?
formation stats at organizing center called centrosome
what happens when the glucose levels are low in the blood and you have not eaten?
glucagon (hormone) triggers the breakdown of glycogen in the liver, glucose levels are high in the cell and then the conformation moves the glucose out of the cell to the blood stream---to make it to other cells that need it
Once the actin monomer ATP binding site has hydrolyzed to ADP what happens to the stability?
this will decrease stability of the filament (which will later promote the de-polymerization of filament
What type of transport is the channel?
passive transport
what does the rate of diffusion depend on
size of molecule and its solubility properties, generally smaller the molecule and more soluble, rate of diffusion is faster
What does the rate of diffusion pass the plasma membrane depend on?
size of molecule and solubility
describe how the channel membrane protein work?
small hydrophillic pores that allow for solutes to pass through
what can pass through the membrane easily that are small hydrophobic ? easy or no?
small hydrophobic molecules O2, CO2, N2 and benzene easy
what are the smaller beta subunits of the Na/K pump?
smaller beta subunits are glyvoproteins for plasma membrane localization
where are K+, Ca2+, Cl- and H+ most plentiful
solute's in a cell's environment
what type of structure do the carrier protein have?
solute-binding site
what kind of molecules can pass via transporter
solutes that are either small organic molecules or inorganic ions
transporters, in contrast to channels, work by
specific binding to solutes
give an example of a stress gated ion channel
sterocillia
The microtubules in a cell form a structural framework that can have all the following functions except which one? A. strengthening the plasma membrane B. holding internal organelles such as the Golgi apparatus in particular positions in the cell C. moving materials from one place to another inside a cell D. creating long, thin cytoplasmic extensions that protrude from one side of the cell
strengthening the plasma membrane
2. protrusion adhere to new surface
*lamellipodia touch down and stick with the help of integrins *integrins are transmembrane proteins -do the adhering to the new surface *integrins capture actin filaments in the cell cortex creating an anchor
what does active transport by ATPase do?
-Maintain extracellular ionic composition -move solutes against an electrochemical gradient
what is the role of the carrier protein in active transport?
-against a concentration gradient -harness energy from ATP
what are the binding sites of the glucose carrier/transport? How does the glucose transporter work?
-binding site of glucose is to the transmembrane segments - one conformation exposes the binding site to the outside of the cell and the other to the inside of the cell. (refer to figure 1.1
what is the role of channels in passive transport?
-down a concentration gradient -no expenditure of energy
Describe the glucose carrier/transporter?
-have 2 conformations -switch back and forth to open and close on each side
what is the function of the intermediate filaments?
-provide tensile strength -increase cells ability to withstand mechanical stress
Why does the Plasma Membrane and its inserted proteins work to maintain the concentration of ions inside and outside of the cell? and why
-to develop membrane potential -to drive cellular response to stimuli
what type of energy do the channel use for ions? Also what type of channel is this?
-use diffusion to move across -ion channel when only ion moved
fill in the blanks: neurons communicate w/ eachother through specialized cells called ____ synapses ________. many neurotransmitter receptors are ligan-gated ion channels that open transiently in the _____postsynaptic_____cell membrane in response to neurotransmitters released by the _____presynaptic _____ cell. ligand-gated ion channels in nerve cell membranes convert _____chemical ______signals into ______electrical ______ones. neurotransmitter release is stimulated by opening of voltage gated _____Ca2+ channels ___ in the nerve terminal membrane
...
what are the steps of shirking a microtubule?
1) Protofilaments containing GDP tubulin peel away from the microtubule wall 2) GDP tubulin is released to the cytosl
What are the 5 purposes of the cytoskeleton
1) adapt shape of the cell 2) organize interior of the cell 3)interact mechanically with enviroment 4)carry out movement 5)support the cytoplasma
what are the two classes of membrane proteins
1) carrier protein (transporter/pump? 2)channels
What is the purpose of the membrane transport?
1) exchange of molecules 2) use of membrane transport proteins 3) maintain internal ion composition 4) control biological process
how does the calcium pump keep extracellular calcium low?
1)ATP binds and then 2 Ca2+ bind 2)aspartic acid is phosphorylated 3)Trigger conformational change Nucleotide binding domain and activator domains get close Leads to rearrangement of transmembrane helices 4)Disrupts Ca2+ binding sights 5)Ca2+ is released into lumen of SR or extracellular space (figure 1.3
How does the Na/K pump works?
1)Pump binds ATP then 3 Na+ ions 2)ATP is hydrolyzed leading to Phosphorylation of pump 3)Conformational change exposes Na To outside (P-pump has low affinity For Na and Na is released) 4)Pump binds 2 K+ ions. Causes Dephosphorylation of pump 5)Pump revert to previous Coformation (deP-pump has higher Affinity for NA than K, so K is Released) 6)Cycle starts again
what are the steps of the formation of the microtublues?
1)gamma tubulin rings are on the surface of centrosome 2)alpha and beta tubulin dimers are added to gamma tubulin via noncovalent bonds *thus making an individual protofilament that has polarity 3) 13 protofilament will then organize into a hollow cylindrical microtubule
what are the 3 types of cytoskeletal filaments
1)intermediate filaments 2) microtubules 3) actin filaments
What is the function of the sodium/ potassium pump?
1)moves K in while moving Na out 2)maintains high (Na) outside the cell becasue Na leaks back in thru other channels or carriers
what are the difference between passive vs. active transport?
1)passive -down the concentration gradient -no energy required by channels and transporters 2)active -against the concentration gradient -energy required by transporters ------ This is for small hydrophillic molecules
why does the glucose use _____ transport?
1)passive transport -glucose moves according to the concentration gradient across the membrane
what is the 3 step process of movement of the cell?
1. push out the protruding leading edge of the cell 2. protrusion adhere to new surface 3. drag the rest of the cell forward by traction
what is the structure of the sodium/posstum pump?
2 alpha and 2 beta subunits
3___ for 2____
3 Na for 2 K. removing 1 positive charge carrier from the intracellular space
what is Na+ mostly balanced by
extracellular Cl-
Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell? (a) Na+ (b) K+ (c) Ca2+ (d) Cl-
A
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________. (a) active transport. (b) free diffusion. (c) facilitated diffusion. (d) passive transport.
A
The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. What type of neurotransmitter is used at these neuromuscular junctions? (a) acetylcholine (b) glutamate (c) GABA (d) glycine
A
Transporters, in contrast to channels, work by ________________. (a) specific binding to solutes. (b) a gating mechanism. (c) filtering solutes by charge. (d) filtering solutes by size.
A
Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? (a) Some channels remain closed and some open completely. (b) All channels open completely. (c) All channels open partly, to the same degree. (d) All channels open partly, each to a different degree.
A
We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees. Which of the following has the lowest rate of diffusion across an artificial membrane? Why? (a) glucose (b) water (c) glycerol (d) ethanol
A
Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? (a) an aquaporin (b) a sodium channel (c) a calcium channel (d) a proton channel
A
Which of the following statements about the cytoskeleton is true? A. All eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm. B. Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end. C. The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another. D. The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell.
Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end
Which of the following best describes the behavior of a gated channel? (a) It stays open continuously when stimulated. (b) It opens more frequently in response to a given stimulus. (c) It opens more widely as the stimulus becomes stronger. (d) It remains closed if unstimulated.
B
When using the Nernst equation to calculate membrane potential, we are making several assumptions about conditions in the cell. Which of the following is not a good assumption? (a) The temperature is 37°C. (b) The plasma membrane is primarily permeable to Na+. (c) At rest, the interior of the cell is more negatively charged than the exterior. (d) K+ is the principal positive ion in the cell.
B
Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? A. Actin filaments would grow shorter because depolymerization would be enhanced. B. Actin filaments would grow longer. C. No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length. D. Actin filaments would grow shorter because new monomers could not be added to the filaments.
Actin filaments would grow longer.
Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport? (a) Na+-coupled (b) K+-coupled (c) ATP-driven (d) light-driven
B
Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion? (a) HCO3- (b) Cl- (c) PO43- (d) OH-
B
Ca2+-pumps in the plasma membrane and endoplasmic reticulum are important for _____________. (a) maintaining osmotic balance. (b) preventing Ca2+ from altering the activity of molecules in the cytosol. (c) providing enzymes in the endoplasmic reticulum with Ca2+ ions that are necessary for their catalytic activity. (d) maintaining a negative membrane potential.
B
Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell? (a) Na+ (b) K+ (c) Ca2+ (d) Cl-
B
Ion channels are classified as membrane transport proteins. Channels discriminate by size and charge. In addition to Na+, which one of the following ions would you expect to be able to freely diffuse through a Na+ channel? Explain your answer. (a) Mg2+ (b) H+ (c) K+ (d) Cl-
B
The Nernst equation can be used to calculate the membrane potential based on the ratio of the outer and inner ion concentration. In a resting cell, membrane potential is calculated taking only K+ ions into account. What is V when Co = 15 mM and Ci = 106 mM? (a) 438.1 mV (b) -52.7 mV (c) 52.7 mV (d) -5.3 mV
B
Which of the following occur without coupling transport of the solute to the movement of a second solute? (a) import of glucose into gut epithelial cells (b) export of Ca2+ from the cytosol (c) export of H+ from animal cells for pH regulation (d) the export of Na+ from cells to maintain resting membrane potential
B
Which of the following statements best reflects the nature of synaptic plasticity? (a) New synapses are created due to the postnatal generation of neurons. (b) Synaptic response changes in magnitude depending on frequency of stimulation. (c) There is a change in the type of neurotransmitter used at the synapse. (d) Neuronal connections are pruned during normal development.
B
You have generated antibodies that recognize the extracellular domain of the Ca2+-pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+? (a) Ca2+-pumps in vesicle membranes keep cytosolic calcium levels low. (b) Ca2+-pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low. (c) Ca2+-pumps in the Golgi apparatus keep cytosolic calcium levels low. (d) Ca2+ concentrations in the cytosol increase at a steady rate.
B
what does the GLUT 2 beta cells and liver cells do in regards to glucose?
Bidirectional 1)Uptake glucose for glycolysis And 2)Release glucose from liver during Gluconeogensis And 3)Free flow beta cell to gauge Serum glc levels
Approximately, how many distinct synapses are established on the dendrites and cell body of a motor neuron in the spinal cord? (a) tens (b) hundreds (c) thousands (d) millions
C
Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following negatively charged ions is not primarily used to buffer positive charges inside the cell? (a) PO43- (b) OH- (c) Cl- (d) HCO3-
C
If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected? (a) The membrane potential is not affected by Na+. (b) It becomes more negative. (c) It becomes more positive. (d) It is permanently reset.
C
Some cells have aquaporins—channels that facilitate the flow of water molecules through the plasma membrane. For these cells, what regulates the rate and direction of water diffusion across the membrane? (a) aquaporin conformation (b) resting membrane potential (c) solute concentrations on either side of the membrane (d) availability of ATP
C
The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? (a) Na+ is bound (b) ADP is bound (c) the pump is phosphorylated (d) the pump changes conformation
C
When the net charge on either side of the plasma membrane is zero, what else is true? (a) There is an equal number of K+ ions on each side of the plasma membrane. (b) The K+ leak channels are open. (c) The electrochemical potential across the membrane is zero. (d) The resting membrane potential is between -20 mV and -200 mV.
C
Which of the following gated ion channels are involved in inhibitory synaptic signaling? (a) voltage-gated Na+ channels (b) voltage-gated Ca2+ channels (c) glycine-gated Cl- channels (d) glutamate-gated cation channels
C
Which of the following statements about resting membrane potential is not true? (a) The resting membrane potential for most animal cells is 0 mV, because the positive and negative ions are in balance. (b) The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells. (c) The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell. (d) At the resting membrane potential, no ions enter or exit the cell.
C
how does calcium release from it concentration gradients interacts with vesicles?
Calcium activates SNARE Proteins expressed on vesicle and membrane surfaces (and other bud related proteins) Mediate docking and fusion of vesicle to membrane this is the exocytosis of insulin
Which of the following statements about the cytoskeleton is false? A. The cytoskeleton is made up of three types of protein filaments. B. Covalent bonds between protein monomers hold together cytoskeletal filaments. C. The cytoskeleton controls the location of organelles in eukaryotic cells. D. The cytoskeleton of a cell can change in response to the environment.
Covalent bonds between protein monomers hold together cytoskeletal filaments.
A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+ 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following could account for the yeast cell's demise? (a) toxic buildup of carbon dioxide inside the cell (b) toxic buildup of ethanol inside the cell (c) diffusion of ATP out of the cell (d) inability to import sugar into the cell
D
Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest). alanine estrogen propanol sodium (a) alanine > propanol > sodium > estrogen (b) sodium > propanol > alanine > estrogen (c) estrogen > propanol > sodium > alanine (d) estrogen > propanol > alanine > sodium
D
Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? (a) by closing Na+ channels (b) by preventing the secretion of excitatory neurotransmitters (c) by opening K+ channels (d) by opening Cl- channels
D
Cells make use of H+ electrochemical gradients in many ways. Which of the following proton transporters is used to regulate pH in animal cells? (a) light-driven pump (b) H+ ATPase (c) H+ symporter (d) Na+-H+ exchanger
D
In a method called patch-clamping, a glass capillary can be converted into a microelectrode that measures the electrical currents across biological membranes. Which of the following is not true about the patch-clamp method? (a) The glass capillary adheres to a "patch" of membrane through the application of suction. (b) The aperture in the glass capillary used to make a microelectrode is about 1 μm in diameter. (c) If the experimental conditions are held constant, fluctuations in electrical currents across the patch of membrane are still observed. (d) Single-channel patch-clamp recordings have demonstrated that gated membrane channels will only open and close in response to specific stimuli.
D
K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? (a) They set the K+ concentration gradient to zero. (b) They set the membrane potential to zero. (c) They disrupt the resting membrane potential. (d) They keep the electrochemical gradient for K+ at zero.
D
Negatively charged ions are required to balance the net positive charge from metal ions such as K+, Na+, and Ca2+. Which of the following negatively charged ions is the most abundant outside the cell and which ion does most often neutralize (written in parentheses)? (a) Cl- (Ca2+) (b) PO43- (K+) (c) PO43- (Ca2+) (d) Cl- (Na+)
D
The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use? (a) voltage-gated (b) extracellular ligand-gated (c) intracellular ligand-gated (d) stress-gated
D
Which of the following is required for the secretion of neurotransmitters in response to an action potential? (a) neurotransmitter receptors (b) Na+-K+ pumps (c) voltage-gated K+ channels (d) voltage-gated Ca2+ channels
D
Which of the following statements about GABA receptors is not true? (a) They are located on postsynaptic membranes. (b) They are ligand-gated channels. (c) They inhibit synaptic signaling. (d) They promote neuronal uptake of Na+.
D
Which of the following statements does not accurately describe the events involved in the propagation of an action potential? (a) An initial influx of Na+ through a small cluster of channels causes local depolarization of the membrane. (b) Local depolarization causes nearby Na+ channels to open. (c) Channels in depolarized regions of the membrane are inactivated until the resting membrane potential is reestablished. (d) The opening of transmitter-gated K+ channels helps to repolarize the membrane.
D
Which of the following statements is true? (a) Amoebae have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior. (b) Bacteria and animal cells rely on the Na+-K+ pump in the plasma membrane to prevent lysis resulting from osmotic imbalances. (c) The Na+-K+ pump allows animal cells to thrive under conditions of very low ionic strength. (d) The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.
D
Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? A. Although both filaments can grow from both ends, the growth rate is faster at the plus ends. B. Nucleotide hydrolysis promotes depolymerization of filaments. C. Free subunits (actin and tubulin) carry nucleoside triphosphates. D. Depolymerization initiates at the plus ends of filaments.
D. Depolymerization initiates at the plus ends of filaments.
Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? A. Free subunits (actin and tubulin) carry nucleoside triphosphates. B. Nucleotide hydrolysis promotes depolymerization of filaments. C. Depolymerization initiates at the plus ends of filaments. D. Although both filaments can grow from both ends, the growth rate is faster at the plus ends.
Depolymerization initiates at the plus ends of filaments.
what happens when you eat a meal and increase circulating blood sugar?
Glucose is high outside the cell so the conformation is open to take in glucose and move it to the cytosol where the concentration is low (at beta cell and other cell types)
what ions can pass through the membrane? easy or not?
H, Na, HCo3, K, Ca2, Cl,Mg Not
what can pass through the membrane that are small uncharged polar molecules? easy or no?
H2O, glycerol, and ethanol easy
Which of the following statements about the function of the centrosome is false? A. Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome. B. Centrosomes typically contain a pair of centrioles, which is made up of a cylindrical array of short microtubules. C. Centrosomes are the major microtubule-organizing center in animal cells. D. Centrosomes contain hundreds of copies of the g-tubulin ring complex important for microtubule nucleation.
Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome.
where is calcium located at?
Mitocohdria ER cytoplasma
Which of the following statements about microtubules is true? A. Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament. B. Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell. C. The centromere nucleates the microtubules of the mitotic spindle. D. ATP hydrolysis by a tubulin heterodimer is important for controlling the growth of a microtubule.
Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament.
describe how the carrier protein works?
Move the solute across the membrane by binding it one side and transporting it to the other side.
You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells. The hypothesis that best explains this localization is ________________. A. MtA is important for the interaction of microtubules with the centrosome. B. MtA binds to GTP-bound tubulin on microtubules. C. MtA will not bind to purified microtubules in a test tube. D. MtA is involved in stabilizing microtubules.
MtA binds to GTP-bound tubulin on microtubules.
give an example of a voltage gated ion channel
Na+, K+, Ca2+
Which of the following statements about organellar movement in the cell is false? A. Organelles are attached to the tail domain of motor proteins. B. Motor proteins involved in organellar movement use ATP hydrolysis for energy. C. Organelles undergo saltatory movement in the cell. D. Only the microtubule cytoskeleton is involved in organellar movement.
Only the microtubule cytoskeleton is involved in organellar movement.
Which of the following statements about organellar movement in the cell is false? A. Organelles undergo saltatory movement in the cell. B. Only the microtubule cytoskeleton is involved in organellar movement. C. Organelles are attached to the tail domain of motor proteins. D. Motor proteins involved in organellar movement use ATP hydrolysis for energy.
Only the microtubule cytoskeleton is involved in organellar movement.
Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments? A. Dimers associate by noncovalent bonding to form a tetramer. B. Phosphorylation causes disassembly during every mitotic cycle. C. They strengthen cells against mechanical stress. D. They are found in the cytoplasm.
Phosphorylation causes disassembly during every mitotic cycle.
How do small nonpolar molecules pass through?
Simple diffusion
Which of the following statements about microtubules is true? (a) Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament. (b) The centromere nucleates the microtubules of the mitotic spindle. (c) Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell. (d) ATP hydrolysis by a tubulin heterodimer is important for controlling the growth of a microtubule.
a
Which of the following statements about actin is false? A. Actin at the cell cortex helps govern the shape of the plasma membrane. B. The dynamic instability of actin filaments is important for cell movement. C. ATP hydrolysis decreases actin filament stability. D. Actin filaments are nucleated at the side of existing actin filaments in lamellipodia.
The dynamic instability of actin filaments is important for cell movement.
Which of the following statements about actin is false? A. Actin at the cell cortex helps govern the shape of the plasma membrane. B. The dynamic instability of actin filaments is important for cell movement. C. ATP hydrolysis decreases actin filament stability. D. Actin filaments are nucleated at the side of existing actin filaments in lamellipodia.
The dynamic instability of actin filaments is important for cell movement.
Which of the following statements regarding dynamic instability is false? A. GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. B. The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end. C. The GTP cap helps protect a growing microtubule from depolymerization. D. Each microtubule filament grows and shrinks independently of its neighbors.
The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.
what are the alpha subunits of the Na/K pump?
They are catalytic portion ----sit of ATP binds, binds Na and K, and P sites
what does the GLUT 4 do in adipose and muscle cells?
They are insulin regulated transporter -Facilitate glucose storage -when there is low insulin, glut 4 are in vesicles (figure 1.2)
What is an electrochemical gradient?
Voltage across the membrane created by charge ions
All intermediate filaments are of similar diameter because ____________. (a) the central rod domains are similar in size and amino acid sequence. (b) the globular domains are similar in size and amino acid sequence. (c) covalent bonds among tetramers allow them to pack together in a similar fashion. (d) there is only a single type of intermediate filament in every organism.
a
Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? (a) Actin filaments would grow longer. (b) Actin filaments would grow shorter because depolymerization would be enhanced. (c) Actin filaments would grow shorter because new monomers could not be added to the filaments. (d) No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length.
a
Which of the following items is not important for flagellar movement? (a) sarcoplasmic reticulum (b) ATP (c) dynein (d) microtubules
a
Which of the following statements about the function of the centrosome is false? (a) Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome. (b) Centrosomes contain hundreds of copies of the γ-tubulin ring complex important for microtubule nucleation. (c) Centrosomes typically contain a pair of centrioles, which is made up of a cylindrical array of short microtubules. (d) Centrosomes are the major microtubule-organizing center in animal cells.
a
Which of the situations below will enhance microtubule shrinkage? (a) addition of a drug that inhibits GTP exchange on free tubulin dimers (b) addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers (c) addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules (d) addition of a drug that blocks the ability of a tubulin dimer to bind to γ-tubulin
a
Which of the following statements about the structure of microtubules is false? A. Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. B. a-Tubulin and b-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments. C. Microtubules are built from protofilaments that come together to make a hollow structure. D. The two ends of a protofilament are chemically distinct, with a-tubulin exposed at one end and b-tubulin exposed at the other end.
a-Tubulin and b-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
give an example of a ligand gated ion channel
acetylcholine receptor, neurotransmitter receptor
What are the two movements the membrane is under
concentraion gradient voltage across the membrane
What type of transport is the carrier protein?
active transport
pumps are transporters that are able to harness energy provided by other components in cells to drive movement of solutes across membranes, against their concentration gradient. this type of transport is called
active transport
what does Calcium act as
acts as 2nd messenger to trigger events: contraction and release of insulin
Which of the situations below will enhance microtubule shrinkage? A. addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers B. addition of a drug that blocks the ability of a tubulin dimer to bind to g-tubulin C. addition of a drug that inhibits GTP exchange on free tubulin dimers D. addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules
addition of a drug that inhibits GTP exchange on free tubulin dimers
The hydrolysis of GTP to GDP carried out by tubulin molecules ________________. A. allows the behavior of microtubules called dynamic instability. B. tips the balance in favor of microtubule assembly. C. occurs because the pool of free GDP has run out. D. provides the energy needed for tubulin to polymerize.
allows the behavior of microtubules called dynamic instability.
What can pass through the membrane that are large uncharged polar molecules? easy or no?
amino acids, glucose, and nucleotides not easy
How is the intermediated filaments anchored
anchored to plasma membrane by cell-cell junction called DESMosomes -allowing neighboring cell to be link
Na+ - K+ pump - name type of transport, energy source and function
antiport, atp, maintain gradients of sodium and K ions across membrane
what type of structure do the channel have?
aqueous pore
The microtubules in a cell form a structural framework that can have all the following functions except which one? (a) holding internal organelles such as the Golgi apparatus in particular positions in the cell (b) creating long, thin cytoplasmic extensions that protrude from one side of the cell (c) strengthening the plasma membrane (d) moving materials from one place to another inside a cell
c
what is the fucntion of actin filaments
essential for cell movements by creating tempoary structures
Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? (a) Although both filaments can grow from both ends, the growth rate is faster at the plus ends. (b) Depolymerization initiates at the plus ends of filaments. (c) Nucleotide hydrolysis promotes depolymerization of filaments. (d) Free subunits (actin and tubulin) carry nucleoside triphosphates.
b
Which of the following conditions is likely to decrease the likelihood of skeletal muscle contraction? (a) partial depolarization of the T-tubule membrane, such that the resting potential is closer to zero (b) addition of a drug that blocks Ca2+ binding to troponin (c) an increase in the amount of ATP in the cell (d) a mutation in tropomyosin that decreases its affinity for the actin filament
b
Which of the following statements about organellar movement in the cell is false? (a) Organelles undergo saltatory movement in the cell. (b) Only the microtubule cytoskeleton is involved in organellar movement. (c) Motor proteins involved in organellar movement use ATP hydrolysis for energy. (d) Organelles are attached to the tail domain of motor proteins.
b
Which of the following statements about skeletal muscle contraction is false? (a) When a muscle cell receives a signal from the nervous system, voltage-gated channels open in the T-tubule membrane. (b) The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction. (c) A change in the conformation of troponin leads to changes in tropomyosin such that it no longer blocks the binding of myosin heads to the actin filament. (d) During muscle contraction, the Z discs move closer together as the myosin heads walk toward the plus ends of the actin filaments.
b
Which of the following statements is false? (a) Cytochalasins prevent actin polymerization. (b) Actin filaments are usually excluded from the cell cortex. (c) Integrins are transmembrane proteins that can bind to the extracellular matrix. (d) ARPs can promote the formation of branched actin filaments.
b
You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells. The hypothesis that best explains this localization is ________________. (a) MtA is involved in stabilizing microtubules. (b) MtA binds to GTP-bound tubulin on microtubules. (c) MtA is important for the interaction of microtubules with the centrosome. (d) MtA will not bind to purified microtubules in a test tube.
b
ion channels are classified as membrane transport proteins. channels discriminate by size and charge. in addition to Na+, which of following ions would you expect to be able to freely diffuse through a Na+ channel. explain
b b/c its positively charged and small enough to fit through channel
why does the membrane block most water-soluble molecules from passing
becuase interior of lipid bilayer is hydrophobic
Which of the following statements about the cytoskeleton is false? (a) The cytoskeleton is made up of three types of protein filaments. (b) The cytoskeleton controls the location of organelles in eukaryotic cells. (c) Covalent bonds between protein monomers hold together cytoskeletal filaments. (d) The cytoskeleton of a cell can change in response to the environment.
c
Which of the following statements is correct? Kinesins and dyneins ____________________. (a) have tails that bind to the filaments. (b) move along both microtubules and actin filaments. (c) often move in opposite directions to each other. (d) derive their energy from GTP hydrolysis.
c
Which of the following structures shorten during muscle contraction? (a) myosin filaments (b) flagella (c) sarcomeres (d) actin filaments
c
You are examining a cell line in which activation of the Rho family member Rac promotes lamellipodia formation. Which of the following statements is most likely to be true? (a) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more unbranched actin filaments than normal cells. (b) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more unbranched actin filaments than normal cells. (c) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells. (d) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more branched actin filaments than normal cells.
c
You are studying nuclear lamins in yeast. Using recombinant DNA technology, you alter the coding sequence of a nuclear lamin gene such that the gene now codes for a nuclear lamin protein that can no longer be phosphorylated when the nuclear envelope is broken down during mitosis. What do you predict would happen if the yeast cell only had the altered nuclear lamin gene (and not the unaltered version)? (a) Mitosis should proceed as usual because the dephosphorylation of the lamin is what is important for nuclear lamina assembly during mitosis, so phosphorylation will not be necessary. (b) Disassembly of the nuclear lamins will occur prematurely because the lamins cannot be phosphorylated. (c) Nuclear lamins will no longer disassemble properly during mitosis. (d) Nuclear lamins will be unable to produce dimers, as coiled-coil formation will be disrupted.
c
the influx of which ion through what type of channel would trigger release of neurotransmittesr into synaptic cleft
calcium, voltage gated calcium channels
what class of membrane requires a conformation change?
carrier protein
where are the intermediate filaments that are vimentin and vimentin-related located?(cytoplasmic)
connective tissue cells, muscle cells, and glial cells
what is an example of cellular response release of insulin?
consume a meal, glucose high in circulation, pancreas responds 1)high carb food- glucose uptake 2)GLUT2-facilitated diffusion 3)glucokinase 4)glycoysis respiration 5) ATP and ADP increases 6)ATP- senstive potassium channels closes 7)depolarization 8) voltage-gated calcium channels open 9)insulin is resleased
what does the movements of the cancer cell require?
coordinated cell polarity (leading edge and trailing back edge) cytoskeletal activity (action of actin filaments, along with myosin ) rearrangement of extracellular matrix that surrounds cell to create a path for cell figure 1.4
where are the intermediate filaments located?
cytoplasm and nucleus
Cell movement involves the coordination of many events in the cell. Which of the following phenomena is not required for cell motility? (a) Myosin-mediated contraction at the rear of the moving cell. (b) Integrin association with the extracellular environment. (c) Nucleation of new actin filaments. (d) Release of Ca2+ from the sarcoplasmic reticulum.
d
For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. (a) stabilizing the filaments once they are formed. (b) increasing the rate at which subunits are added to the filaments. (c) promoting nucleation of filaments. (d) decreasing the binding strength between subunits on filaments.
d
Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments? (a) They strengthen cells against mechanical stress. (b) Dimers associate by noncovalent bonding to form a tetramer. (c) They are found in the cytoplasm. (d) Phosphorylation causes disassembly during every mitotic cycle.
d
The hydrolysis of GTP to GDP carried out by tubulin molecules ________________. (a) provides the energy needed for tubulin to polymerize. (b) occurs because the pool of free GDP has run out. (c) tips the balance in favor of microtubule assembly. (d) allows the behavior of microtubules called dynamic instability.
d
Which of the following statements about actin is false? (a) ATP hydrolysis decreases actin filament stability. (b) Actin at the cell cortex helps govern the shape of the plasma membrane. (c) Actin filaments are nucleated at the side of existing actin filaments in lamellipodia. (d) The dynamic instability of actin filaments is important for cell movement.
d
Which of the following statements about the cytoskeleton is true? (a) All eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm. (b) The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell. (c) The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another. (d) Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.
d
Which of the following statements about the structure of microtubules is false? (a) Microtubules are built from protofilaments that come together to make a hollow structure. (b) The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end. (c) Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. (d) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
d
Which of the following statements regarding dynamic instability is false? (a) Each microtubule filament grows and shrinks independently of its neighbors. (b) The GTP cap helps protect a growing microtubule from depolymerization. (c) GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. (d) The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.
d
Which of the statements below about intermediate filaments is false? (a) They can stay intact in cells treated with concentrated salt solutions. (b) They can be found in the cytoplasm and the nucleus. (c) They can be anchored to the plasma membrane at a cell-cell junction. (d) Each filament is about 10 μm in diameter.
d
You are interested in understanding the regulation of nuclear lamina assembly. To create an in vitro system for studying this process you start with partly purified nuclear lamina subunits to which you will add back purified cellular components to drive nuclear lamina assembly. Before you start doing experiments, your instructor suggests that you consider what type of conditions would be most amenable to the assembly of the nuclear lamina from its individual subunits in vitro. Which of the following conditions do you predict would be most likely to enhance the assembly of the nuclear lamina? (a) addition of phosphatase inhibitors (b) addition of ATP (c) addition of a concentrated salt solution that is 10 times the concentration normally found in the nucleoplasm (d) addition of protein kinase inhibitors
d
Your friend works in a biotech company that has just discovered a drug that seems to promote lamellipodia formation in cells. Which of the following molecules is unlikely to be involved in the pathway that this drug affects? (a) Rac (b) ARP (c) actin (d) myosin
d
For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. A. increasing the rate at which subunits are added to the filaments. B. stabilizing the filaments once they are formed. C. decreasing the binding strength between subunits on filaments. D. promoting nucleation of filaments.
decreasing the binding strength between subunits on filaments.
For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. A. stabilizing the filaments once they are formed. B. decreasing the binding strength between subunits on filaments. C. increasing the rate at which subunits are added to the filaments. D. promoting nucleation of filaments.
decreasing the binding strength between subunits on filaments.
you add NaCl to extracellular fluid and effectively double amount of extracellular Na+ cation. how does this affect action potential you measure
double the amplitude. if you halved NaCl, amplitude would cut in half.
what is Dynamic instability driven by?
driven by the binding of GTP to tubulin dimers that is hydrolyzed after dimer is added to the prtpfilament
what does each free actin monomer contains?
each free actin monomer has a binding site for 1 ATP - once incorporated into the filament (polymerization), the ATP is hydrolyzed to ADP
what type of filaments are in the cytoplasmic that are keratin located at? (cytoplasmic)
epithelail cells
what is passive transport base on electrochemical gradient?
gradient determines the direction of the charged solute during passive transport
what type of chemical signals do a tumor cell recevies?
growth factor
transporter
has moving parts, can shift small molecules from one side to the other by chaning its shape
what would happen to a cell if you placed it in a hypertonic solution? hypotonic?
hypertonic means high salt outside, water would rush out of cell and shrivel. hypotonic means low salt outside, water would rush in and swell
smal nonpolar molecules
i.e. O2, CO2, readily dissolve in lipid bilayers and rapidly diffuse
What does the channel protein require?
if open, will let solutes pass if they have the right size and charge -trapdoor like
where is K+
inside cell
Is calcium high or low in the cell?
intracellular calcium concentrations must be low
what is the hallmark of cancer cell invasion?
is the ability of one cell to break away and away from tumor and move
why are microtublues unstable?
it allows the assembly and dissassembly in different locations
what would happen to action potential if you added a chemical that prevented chloride from fitting through channels
it would not be impacted b/c chloride ions wouldn't flow in
what does the morpholgical changes of the cell show?
lead to detachment of cell from tumor -promote formation of lamellopodia
uncharged polar molecules
molecules with an uneven distribution of charge diffuse reapidly if small enough. H20 (18 daltons passes), ehtanol (46 daltons), glycerol (92 daltons) is less rapid and glucose (180 daltons) bare crosses
you figured out how to make a giant squid axon express high levels of voltage gated chloride channel but only to half way point along axon. how would you expect action potential to look along length of axon
move until it hit voltage gated chloride channels which would surpress generation of action potential
where are the intermediate filaments of neurofilaments located at? (cytoplasmic)
nerve cells
what would happen to resting membrane potential if inner channel of K+ leak channel decreased in size by half?
no K+ would be able to leak out and resting membrane potential would become more positive
ions and charged molecules
no matter hw smal, highly impermeable. molecules' charge and strong electrical attraction to water molecules inhibit them from entering hydrocarbon phase of bilayer
what would happen to action potential if you added an inhibitor of voltage gated K+ channel
not be able to reset to resting potential and refractory period would last longer
where are the itermediated filaments of the nuclear located at? and what are they called
nuclear lamins and in all animal cells
Which of the following statements is correct? Kinesins and dyneins ____________________. A. have tails that bind to the filaments. B. derive their energy from GTP hydrolysis. C. move along both microtubules and actin filaments. D. often move in opposite directions to each other.
often move in opposite directions to each other.
it is thought glucose transporter switches btwn two conformational states in completely random fashion. how is it possible for such a system to move glucose across membrane efficiently in single direction
opening of glucose transporter on one side of membrane or other is random, but binding of glucose into binding site of transporter is not random. affinity between glucose molecule and transporter governs binding event: at high glucose concentrations complex formation is favored, at low concentrations, dissociation of glucose from transporter is favored. as long as there is a large concentration gradient, efficient transport can occur by rules of binding equilibria
where is Na+
outside cell
how many domains do the calcium pump contains?
pump has 4 domains
na+-K+ atpase also known as Na+-K+ pump. it is responsible for maintaining high extracellular sodium ion concentration and high intracellular potassium ion concentration. what happens immediately after pump hydrolyzes ATP
pump is phosphorylated
what must happen for a cell not to be torn apar
quantity of positivie charge inside must be balanced almost equally by external negative charge
how does the tumor cell show morphological changes
rearrangement of actin in the cytoskeleton decrease interaction of the cell to neighboring tumor cells.
what does the NA/K ATPase pump require?
requires ATP hydrolysis and therefore pump is also an ATPase enzyme
what does the carrier protein require?
requires that the solute fit in the specific binding site (selective) -turnstile-like
Which of the following structures shorten during muscle contraction? A. actin filaments B. myosin filaments C. flagella D. sarcomeres
sarcomeres
Which of the following items is not important for flagellar movement? A. ATP B. dynein C. microtubules D. sarcoplasmic reticulum
sarcoplasmic reticulum
Na+ - glucose -name type of transport, energy source and function
symport, Na+ gradient, import glucose into cell against its gradient
All intermediate filaments are of similar diameter because ____________. A. the central rod domains are similar in size and amino acid sequence. B. the globular domains are similar in size and amino acid sequence. C. covalent bonds among tetramers allow them to pack together in a similar fashion. D. there is only a single type of intermediate filament in every organism.
the central rod domains are similar in size and amino acid sequence.
All intermediate filaments are of similar diameter because ____________. A. covalent bonds among tetramers allow them to pack together in a similar fashion. B. there is only a single type of intermediate filament in every organism. C. the globular domains are similar in size and amino acid sequence. D. the central rod domains are similar in size and amino acid sequence.
the central rod domains are similar in size and amino acid sequence.
describe cell movement?
the meshwork cell cortex allows rearrangement of actin filaments to allow change in cell shape and locomotion (crawling)
what is the cell cortex?
the meshwork cortex supports plasma membrane and gives mechanical strength it interacts with acting binding proteins
what is dynamic instability?
the polymerization and depolymerization of microtubules
How is the movement of the cell dependent on?
the response is dependent on a chemical signal or stimuli
What drives calcium into the cell?
there is a large electrochemical gradient driving Ca into the cell
ion channels
tiny hydrophilic pores which only allow inorganic molecules to diffuse
What is the purpose of the calcium ATPase pump
to keep intracellular (cytosolic) calcium low
what are the two main classes that mediate transfer of molecules across membrane
transporter, channel
T or F a channel can only mediate passive/facilitate diffusion
true
T or F transports can mediate active transport
true
t or f K+ leak channel allows potassium to flow down concentration gradient
true
What are microtubles made from?
tubulin
where are actin filaments most concentrated at?
under plasma membrane in area called cell cortex
what would happen to directionality of action potential if you expressed mutant voltage gated sodium channel that couldn't enter inactivated state
unidirectional propogation would be compromised since action potential now able to go backwards b/c voltage gated Na channels in polarized membrane behind action potential will continue to let Na+ flow into cell
Ca2+ pump - name type of transport, energy source and function
uniport, ATP, pumps Ca2+ out of cytosol
bacteriorhodopsin - name type of transport, energy source and function
uniport, light, pumps protons out of cell
what is ATP-driven pumps?
use ATP hydrolysis to go against gradient (often two metabolites are coupled together to maintain cell membrane potential
what is K+ balance by
variety of negatively charged intracellular ions (anions)
What characteristic can a molecule pass through that need help passing?
water soluble large uncharged charged ion-use active transport
