Mastering Week 7
Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released.
3, 1, 5, 2, 4
Where would RNA polymerase attach?
A
Which of these is a signal molecule?
A
Which of these is a receptor molecule?
B
Bacterial and eukaryotic cells primarily control gene expression at the level of transcription. If instead cells exerted control of gene expression primarily at the post-translational level, what would be different?
Cells would expend significantly more energy.
The letter A indicates___
DNA double helix
Two potential devices that eukaryotic cells use to regulate transcription are
DNA methylation and histone modification
How would decreasing the stability of an mRNA impact the amount of protein encoded by that mRNA?
Fewer proteins will be produced by that mRNA.
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged.
Are histone deacetylases (HDACs) associated with negative or positive control of gene expression? Why?
Negative control, because they make DNA less accessible for transcription
Which statement most accurately explains how some signals are amplified?
Second messengers are produced.
Which answer best explains how certain patterns of histone acetylation or DNA methylation could influence whether a cell became a muscle cell or a brain cell?
They could affect which sets of genes are transcribed in different cell types.
How do only certain cells respond to particular signaling molecules that may be sent throughout the body?
They express the appropriate receptor.
Different body cells can respond differently to the same peptide hormones because___.
a target cell's response is determined by the components of its signal transduction pathways
Protein kinase is an enzyme that _____.
activates or inactivates other proteins by adding a phosphate group to them
Which of the following allows more than one type of protein to be produced from one gene?
alternative forms of RNA splicing
Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ___.
amplify the original signal many times
Steroid hormones bind to receptors inside the cell and alter their conformation. The hormonereceptor complex is then transported into the nucleus, where it can directly affect gene expression. To get from the location where the receptor binds the hormone to its site of action, the hormonereceptor complex must___.
be transported through the nuclear pore complex
Blood sugar is regulated by two pancreatic hormones—insulin and glucagon. When blood sugar rises, insulin is released; it binds to receptors and, through signal transduction, results in an increase in glucose uptake by cells, which effectively lowers blood glucose levels. When blood sugar decreases, glucagon is released, binds to cell receptors, and causes glucose to be released into circulation, thereby increasing blood glucose levels. Diabetes mellitus is a disorder that results from excessively high levels of blood glucose. Type II diabetics have normal to elevated levels of insulin. What, then, might be causing their elevated blood glucose levels?
defective receptors
The activation of receptor tyrosine kinases is characterized by___.
dimerization and phosphorylation
Muscle cells differ from nerve cells mainly because they___
express different genes
If you were to observe the activity of methylated DNA, you would expect it to ____
have turned off or slowed down the process of transcription
In a nucleosome, the DNA is wrapped around ___
histones
The letter C indicates ____.
histones
Which of the following is characteristic of a steroid hormone action?
internal receptor binding
A G-protein receptor with GTP bound to it _____.
is in its active site
A signal molecule is also known as a(n) _____.
ligand
A gene-regulation strategy that is unique to eukaryotic cells is___.
mRNA processing
Which of the following levels of gene expression allows the most rapid response to environmental change?
post-translational control
signal transduction pathway is initiated when a __ binds to a receptor.
signal molecule
The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because___.
steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane
A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's___.
target cell
Which of these is the second of the three stages of cell signaling?
transduction
