Cellular Communication HW
Phosphorylation is always used to activate enzymes during epinephrine signaling.
False
Signal amplification involves all except for one of the following steps in a signal cascade. Which step is NOT involved?
GPCR releases a signal into the extracellular environment
Which of the following are phosphorylated during normal EGF signaling. Select any/all that apply.
- nuclear transcription factors that promote cell growth, - EGF receptor, - protein kinase 3, - protein kinase 2
If a yeast cell experiences an environment with elevated glucose levels, it will increase its uptake of glucose. Describe the mechanism by which the yeast can detect and then react to the presence of the extracellular glucose.
Glucose binds to glucose receptors, which initiates the increase of glucose transporter proteins
A mutation that alters a G-protein's affinity for GDP, making it less likely to release GDP even when stimulated by a receptor, will have what effect on the cell signaling pathway in which it is involved?
The pathway will be underactivated
EGF (epidermal growth factor) is an example of which of the following?
a ligand
When epinephrine binds to its G-protein linked receptor, the second messenger production for cell signaling occurs when __________________.
adenylyl cyclase is activated producing cyclic adenosine mono-phosphate (cAMP).
The advantage of second messengers is best described as
amplification of the signal
During extracellular signaling, ligands bind to
cell surface receptors, on the exterior of the plasma membrane
A substrate binding to an enzyme is conceptually most similar to a signal molecule binding to a
receptor
During cellular communication, the creation of second messengers in signal transduction offers at least two advantages, amplification and
speed
A tyrosine kinase receptor is activated by which of the following?
the phosphorylation of the receptor after binding the ligand
When a receptor binds to a ligand, what actually causes activation and communication to occur?
the receptor is a protein, which physically changes shape (conformational change) due to interaction with the ligand.
Mutations in components of the EGF signaling pathway often lead to cancer.If the Ras protein in the EGF signaling pathway was mutated so that it could not hydrolyze GTP (and was thus always bound to GTP), which of the following options would be a good choice as a potential chemotherapy drug to treat the cancer?
A drug that inhibits the phosphorylation ability of one of the protein kinases in the protein kinase cascade.
What is autophosphorylation, in the context of cell signalling?
Autophosphorylation is a biochemical process in which a phosphate is added to a protein kinase by itself.
When a ligand binds to an enzyme-linked receptor, how is that analogous to when a substrate binds to a cytosolic enzyme's active site?
Both events cause a conformational change that allows for catalysis.
The structure of a signal molecule helps determines its mechanism of signaling. Signal molecules can interact with either intracellular or extracellular receptors. For a signal molecule to bind with an intracellular receptor it must be able to pass through the cellular membrane. Lipid-soluble hormones such as estrogens bind their intracellular receptors primarily by _______________________.
diffusing through the cell membrane
Insulin is normally secreted from the pancreas and then travels through your circulatory system to bind to receptors on (for examples) muscle cells, which then increase glucose uptake from the blood. This is an example of which of the following types of signaling?
endocrine signaling
Diabetics can be given insulin as an injection which then travels through the blood and binds to receptors on cells throughout the body, thereby increasing glucose uptake. In this example, insulin is an example of a
ligand
We talked about several stages or steps of cell signaling in eukaryotes. Which of the stages described here typically occurs in the cytoplasm?
signal transduction, for example a protein kinase cascade
