Cell communication
Describe how cells communicate with each other over short distances
paracrine
Describe three types of receptors
Gproteins receptors
Ligand gated ion channels receptors
receptor enzyme tyrosine kinase receptors
Describe effects, reactions, or results to signal pathways
cell may create new signal for other cells,
cell may alter gene expression to create new protein,
cell may initiate cell death
Which of the following correctly describes the role of cyclins in the regulation of the cell cycle?
Cyclins activate CDKs, which then phosphorylate target proteins to regulate the cell cycle.
Describe when and why cells have checkpoints
G1 checkpoint = Major = large enough cell size, nutrients, growth factors present.
G2 checkpoint = MAjor = DNA replicated properly (important for cancer)
M checkpoint = Major = spindle fibers are lined up equally
S checkpoint = minor (DNA replicated properly)
Describe how plants communicate with juxtacrine
plasmodesmata
Describe the benefits and challenges of signal transduction
benefits = outside message can get into cell indirectly having influence inside the cell. multisteps can be magnified, give more ways to coordinate steps or regulate steps such as drugs can help manipulate the pathway.
challenges = changes to signal can cause breaks/inhibitions or disease.
Describe similar and differences between positive and negative feedback loops. Give examples of each.
positive feedback = a signal gets modified to continue making more of result in same positive resulting direction so breast feeding makes more milk and more feeding makes even more milk.
negative feedback = a signal goes back to inhibit the making of more signals. high blood sugar releases more insulin. insulin lowers blood sugar so less insulin is released
A mutation causes a cell to produce a nonfunctional p53 protein. What is the most likely consequence of this mutation?
Damaged cells may continue to divide, potentially leading to cancer.
Describe role of p53 in regulating cell cycle?
Activated p53 promotes cell cycle arrest to allow DNA repair and/or apoptosis to prevent the propagation of cells with serious DNA damage through the transactivation of its target genes implicated in the induction of cell cycle arrest and/or apoptosis
Describe how/why a neurotransmitter can have a receptor on the surface of the membrane versus in the cytosol
Hydrophobic such as gases and Hydrophobic ligands have receptors inside cells.
Hydrophilic and large ligands are outside cells.
Describe second messenger and give two examples
second messenger is a chemical in the cell that brings about response in cell
examples = cyclic GMP, cyclic AMP, Ca+2
A cellular response pathway is controlled by a negative feedback loop where the final activated protein (a transcription factor) promotes the expression of a protein phosphatase enzyme. This phosphatase dephosphorylates and deactivates an upstream protein kinase in the cascade. If a chemical inhibitor prevents the phosphatase from binding to its target kinase, what is the most likely consequence for the cellular response?
The pathway will enter a state of continuous activation, resulting in an exaggerated or uncontrolled cellular response.
What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase?
+100%
Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (GSK3B) can act either as an oncogene or as a tumor suppressor.
What predicts how GSK3B mutations can lead to the development of cancer?
Cells with inactive GSK3B fail to trigger apoptosis.
A pharmaceutical researcher is studying a novel chemical compound that acts as a potent inhibitor of the enzyme adenylyl cyclase. If this compound is applied to a liver cell responding to epinephrine via a G-protein-coupled receptor (GPCR) pathway, what would be the most immediate and direct consequence on the signaling cascade within the cell?
The intracellular concentration of the second messenger cyclic AMP (cAMP) would decrease significantly.
Insulin is a hormone that initiates a signal transduction pathway by binding to a receptor tyrosine kinase (RTK) on the cell surface. Which of the following events would immediately follow the binding of insulin to its receptor?
The receptor would dimerize, leading to the phosphorylation of its own tyrosine residues.
The depolarization phase of a neuron's action potential involves positive feedback: the initial opening of some voltage-gated Na+ channels allows Na+ to rush in, which further depolarizes the membrane, causing more Na+ channels to open. A neurotoxin is introduced that slightly reduces the voltage sensitivity of these Na+ channels, meaning a stronger initial stimulus is required to open them. How does this change affect the positive feedback mechanism?
The self-amplification process will only occur if the initial stimulus is strong enough to reach a higher, new threshold.
During which checkpoint does the cell verify that DNA replication has been completed accurately before entering mitosis?
G₂ checkpoint
Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing.
Which condition will most likely cause a normal body cell to become a cancer cell?
The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.
Vertebrate immune responses involve communication over short and long distances. What explains how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?
The proteins interact directly with proteins on the surfaces of other cells.
In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell.
What best describes the role of cyclic AMP in the signal transduction pathway?
It acts as a second messenger that helps relay and amplify the signal within the cell.
In a calcium-mediated signal transduction pathway, the second messenger Ca2+ activates a kinase (Kinase A). Kinase A subsequently phosphorylates a membrane pump, causing it to rapidly export Ca2+ back out of the cytosol. This is an example of a negative feedback loop regulating the Ca2+ concentration. What would be the result if a mutation made Kinase A unable to phosphorylate the Ca2+ pump?
The Ca2+ concentration would remain elevated for a prolonged period, extending the cellular response.
DOUBLE JEOPARDY!!!! The progression of eukaryotic cells through the cell cycle is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). When DNA damage occurs, the tumor suppressor protein p53 can inhibit the cycle to allow for DNA repair. Design an experiment to test the effect of UV-induced DNA damage on cell cycle progression in cultured cells. Include the control and measurable outcome.
Independent Variable = cells exposed to sun light
Dependent Variable = Number of cells that progress to different stages of mitosis, namely G1, G2, M (checkpoints) OR amount of cyclin present in cell OR amount of MPF present in cell OR amount of proteins from transcribed p53 present in cell
Control Variables = same type/amount cell. same nutrient/container/temperature for cell, same measuring equipment/procedure/time...
Negative Control Trial = cells exposed to no light
Positive Control Trial = cells exposed to abnormally strong UV-C radiation
Uncontrolled variables = any control variable that was not kept the same
Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the CDC15 gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which predicts the effect of the cell cycle arrest on proliferating yeast cells?
The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.