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Flashcards in Midterm 3 Deck (108)
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Which of the following statements about the carbohydrate coating of the cell surface is false?
(a) It is not usually found on the cytosolic side of the membrane.
(b) It can play a role in cell-cell adhesion.
(c) The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain.
(d) Specific oligosaccharides can be involved in cell-cell recognition.

(c) The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain.


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?

(c) the pump is phosphorylated


We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for?

(d) FRAP


Which of the following statements about iPS cells is false?

(b) iPS cells created from mouse cells can differentiate into almost any human cell type.


It is possible to follow the movement of a single molecule or a small group of molecules. This requires the use of antibodies linked to small particles of gold, which appear as dark spots when tracked through video microscopy. What is this method called? What does the abbreviation stand for?

(b) SPT


The tryptophan operator ___________________________.

(b) binds to the tryptophan repressor when the repressor is bound to tryptophan.


Which of the following statements about the Lac operon is false?

(a) The Lac repressor binds when lactose is present in the cell.


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?

(b) K+-coupled


The modular nature of the Eve gene's regulatory region means that ______.

(a) there are seven regulatory elements and each element is sufficient for driving expression in a single stripe.


What do you predict would happen if you replace the Lac operator DNA from the Lac operon with the DNA from the operator region from the tryptophan operon?

(b) The Lac operon will not be transcribed when tryptophan levels are high.


Which of the following statements about differentiated cells is true?
(a) Cells of distinct types express nonoverlapping sets of transcription factors.
(b) Once a cell has differentiated, it can no longer change its gene expression.
(c) Once a cell has differentiated, it will no longer need to transcribe RNA.
(d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

(d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.


The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which focal adhesions are formed to promote cell motility?

(b) proteins are tethered to the extracellular matrix


Membrane curvature is influenced by the differential lipid composition of the two membrane monolayers. Which factor do you think has the largest impact on the curvature of biological membranes?

(d) size of the lipid head group


When the net charge on either side of the plasma membrane is zero, what else is true?

(c) The electrochemical potential across the membrane is zero.


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


Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol?

(d) membrane thickness


Which of the following statements does not accurately describe the events involved in the propagation of an action potential?

(d) The opening of transmitter-gated K+ channels helps to repolarize the membrane.


Ca2+-pumps in the plasma membrane and endoplasmic reticulum are important for _____________.

(b) preventing Ca2+ from altering the activity of molecules in the cytosol.


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)?

(d) Cl- (Na+)


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.

(b) H+


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?

(b) K+


The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins, such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle-specific genes?

(c) During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells.


The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins?
(a) intercellular communication
(b) selective permeability
(c) cellular movement
(d) import/export of molecules

(b) selective permeability


The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell.

(a) oligosaccharide


In the photosynthetic archaean Halobacterium halobium, a membrane transport protein called bacteriorhodopsin captures energy from sunlight and uses it to pump protons out of the cell. The resulting proton gradient serves as an energy store that can later be tapped to generate ATP. Which statement best describes how bacteriorhodopsin operates?

(b) The absorption of sunlight triggers a shift in the conformation of the protein's seven, membrane spanning α helices, allowing a proton to leave the cell.


Which of the following gated ion channels are involved in inhibitory synaptic signaling?

(c) glycine-gated Cl- channels


Using genetic engineering techniques, you remove the sequences that code for the ribosome-binding sequences of the bacterial LacZ gene. The removal of these sequences will lead to ___________.

(d) translational inhibition of the LacZ mRNA.


The owners of a local bakery ask for your help in improving a special yeast strain they use to make bread. They would like you to help them design experiments using RNA interference to turn off genes, to allow them to test their hypothesis that certain genes are important for the good flavors found in their bread. Of the components in the following list, which is the most important to check for in this yeast strain if you'd like this project to succeed?

(b) the presence of genes in the genome that code for RISC proteins


Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference?
(a) unsaturated hydrocarbons
(b) longer hydrocarbon tails
(c) higher levels of sterols
(d) larger head groups

(a) unsaturated hydrocarbons


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?

(c) solute concentrations on either side of the membrane