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Chapter 6 -- Part 2: Cell Communication
In response to excess sugar in the blood, the pancreas makes a hormone called lysine, which is released into the blood.
The hormone regulates the amount of sugar in the body.
The signaling molecule is binding to the insulin receptor.
The formation of an RTK dimer and autophosphorylation can be triggered by binding.
The complex binding to andphosphorylates aninsulin response protein.
Several signaling cascades are initiated by this response protein.
In muscle cells, one cascade leads to the formation of glycogen, which is used for short-term energy storage, and the other leads to the transport of glucose into the cell.
In the liver cells, the synthesis of glycogen is stimulated.
The pathway leads to the formation of triglyceride in fat cells.
The next mitogen kinase in the sequence is phosphorylated by one of the mitogen kinases.
In this way, MKKK is activated.
When a GTP replaces a GDP, the GProtein associated with a GPCR is activated, but the series of steps that define the pathways of these two receptors is very different.
The small molecule that diffuses across the plasma is called the ligands.
Second messengers, like IP3 that are products of a signal transduction pathway, are included in ligands.
Cell types vary in their response to a particular receptorProtein like other kinds of transduction pathways.
Various molecule specific to individual cells may act as coactivators.
The nucleus may be the location of the target of the activity.
A signaling molecule enters the body.
The signaling molecule can be a first messenger molecule or a second messenger molecule that is introduced into the cytoplasm.
The nucleus or the cytoplasm may be where the receptor is located.
In some cases, the release of an inhibitor prevented the receptor from functioning.
The transcription of genes is promoted by the binding of the receptor-signal complex to the DNA.
Negative feedback mechanisms shut down the release of hormones into the blood.
The signaling molecule diffuses across the cell wall.
The now activated complex moves to the nucleus, where it binding to DNA and promoting transcription of genes that direct cellular activities.
The expression of genes depends on cell type and gender.
In males, testosterone stimulates the development of sperm cells in the testes, but in muscle cells, it causes the production of muscle fibers.
In mammary cells, estrogen inactivates genes that direct cells in the uterus to prepare for pregnancy.
External signals have a strong influence on how genes express information about a cell.
Signals are sometimes inaccurately acted upon due to the signal transduction pathway being distorted.
There are two examples.
The normal activity of GCPRs of intestinal cells is disrupted when the water is contaminated.
The GTP attached to the G protein can't be converted back to a GDP, so it can't be deactivated.
When locked in its active state, the GProtein regulates the concentration of Cl- in these cells.
In response, the cell is continuously moved out of it's location.
The water goes into the intestines.
If not treated, the idiocy can lead to dehydration and death, and the idiocy can assist thebacteria in returning to the water supply.
Normally, cell division is highly regulated, with multiple checkpoints during a cell cycle to ensure that the process is progressing correctly.
Growth factors can cause the activation of atrypsinogen.
The transcription factor is activated when the MAK cascade is initiated.
If the DNA is damaged, p53 directs the enzymes to repair it.
The cell division can proceed once repaired.
The proliferation of damaged cells can be prevented if repair is unsuccessful.
Cell division progresses even if the DNA is damaged as a result of this.
A proliferation of cancer cells is caused by continued cell division.
A review of the material presented in this chapter is provided by the questions that follow.
They can be used to evaluate how well you understand the concepts.
AP multiple-choice questions are often more general, covering a broad range of concepts.
The two practice exams in this book are for these types of questions.
Four possible answers or sentence completions are followed by each of the following questions or statements.
The one best answer or sentence is what you choose.
The answer in the key can be used more than once or not at all.
The questions that follow are typical of an entire AP exam question or just that part of a question that is related to this chapter.
There are two types of questions on the AP exam.
It takes about 20 minutes to answer a long free-response question.
Sometimes they offer you a choice of questions to answer.
6 minutes is the time it takes to answer a short free-response question.
diagrams can be used to supplement your answers, but a diagram alone is not adequate.
Two aspects of their activity are the same despite the differences.
The two aspects of their mechanisms should be described in two or three sentences.
There are different ways in which a G protein-coupled receptor and a protein kinase receptor can phosphorylate a cytoplasm.
In three or four sentences, explain how the two signaling mechanismsphosphorylate a protein kinase.
An example of the pathway can be provided.
Because it is a large molecule, it is charged.
As a result, it is not able to cross.
It must never enter the cell.
Steroids are non-polar molecules that can travel through the plasma membrane.
Cortisol binding to an intracellular receptor is what happens after crossing the membrane.
The signaling molecule does not bind to DNA or mRNA, but rather stimulates the appropriate chemical responses.
Second messengers are small.
There are transcription factors.
Plants and animals have gap junctions that allow for a passageway between adjacent cells.
There are small gaps between nerve cells.
Paracrine signaling occurs among nearby cells, while endocrine signaling occurs for cells separated by large distances.
When a three-dimensional conformational change takes place, a receptor is activated.
The new arrangement of atoms opens passageways or exposes active sites for binding.
Each step of the signaling cascade can lead to multiple reactions.
Each reaction is the beginning of the next step in the cascade.
The signal is amplified by each step.
Because there are multiple participants, the signaling cascade is more susceptible to the influence of mutations, which can have a negative effect on the ultimate product of the signal.
Without assistance, nonpolar ligands can cross themembrane.
They enter the cell and bind to it.
The GProtein is activated by the exchange.
There is a GTP exchange for GDP that can also occur for a RTK pathway, but it occurs on a cytoplasmic protein.
When a ligand is binding to a receptor, it causes it to form a dimer with another.
The groups are attached to themselves by the dimer.
There is a nearby GProtein.
The passageway for ion to enter or exit the cell is provided by a gate.
The second messengers are activated by a GPCR.
The binding of a ligand is required for each of the receptor proteins.
The binding of the ligand to thereceptor causes a change in its three-dimensional structure.
When a GPCR is activated, it causes a second GProtein to be activated, which in turn causes a third GProtein to be activated.
The binding of the signalling molecule to the receptor causes a conformational change in it.
The last step in the descriptions of the pathways is deactivating.
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