Practicing FRQs is a great way to prep for the AP exam! Review student responses for a Unit 4 FRQ and corresponding feedback from Fiveable teacher Caroline Koffke. Then view the most common and thorough responses that receive full credit, also provided by Caroline Koffke.
The FRQ Practice Prompt
Cells have a number of regulatory mechanisms in place in order to ensure proper growth.
a.) Name one cellular regulatory mechanism and how it prevents a cell from replicating if it is not supposed to.
b.) Name one reason why a cell would be given the signal to STOP replicating.
c.) What type of signaling is used for long-distance signals that can reach any cell type? Explain.
Student Samples and Teacher Feedback
Student Sample 1
A) Cells use checkpoints in between G1 and S phase to make sure the cells DNA has not been damaged in some irreparable way.
B) Damaged DNA would be flagged at the checkpoint phase and if it was not able to be repaired in some way the cell will under go apoptosis. This ensures that the damaged DNA will not be replicated later on in Mitosis, which could cause cancer, from a rapid overgrowth of cells with damaged DNA.
C) Hormones are used for long distance signaling, the non-polar lipid hormones can be diffused through the plasma membrane because they are lipids. However, non lipid soluble hormones have to stick to a receptor on the outside of the target cell since they are water-soluble and cannot go through the plasma membrane.
Awesome job! You received 3/3 points for your response. Your answer to part C is very thorough! Keep up the good work.
Student Sample 2
A) One cellular regulatory mechanism is the checkpoint that occurs at the end of the g2 phase in cellular division. This checkpoint allows to cell to continue only if its DNA has been replicated as planned.
B) One reason a cell would be given the signal to stop replicating is if it has a mutation in its dna, which could be harmful.
C) Endocrine signaling is used for long distance communication because they use hormones. For example a steroid, which don’t degrade easily and can get through the cell membrane without needing a specific receptor. This means that the signal is able to affect all cells.
Great job! You received 3/3 points for your response. Keep up the good work!
Student Sample 3
a.) One cell regulatory mechanism are checkpoints in the cell cycle at the end of G1, S, and during mitosis. These checkpoints make sure that the cell has correctly gone through each stage of the cell cycle up to that point. Thus, if something is not correct, the cell is able to tell, and will stop the cell from continuing throughout the cycle and will prevent the cell from replicating.
b.)One reason a cell would be given the signal to stop replicating is before anaphase in mitosis. The spindles may not all properly be attached to the chromosomes, thus, when the chromosomes are pulled to opposite poles, there will be an unequal amount of chromosomes in each cell. This can cause many issues for a cell and can stop it from properly growing and performing its function. Thus, at the checkpoint, the cell would be given the signal to stop.
c.) Endocrine signalling is used for long-distance signals. In this type of signaling, a hormone is secreted from the cell. The hormone travels through the bloodstream, thus it can reach virtually anywhere cell type in the body.
Wonderful response! You received 3/3 points.
Student Sample 4
a) One regulatory mechanism that prevents a cell from replicating if it is not supposed to are the various cell cycle checkpoints found throughout the cell cycle. Replication is prevented by these checkpoints when the concentration of CDK-Cyclin complexes aren’t high enough, thus preventing the cell from moving on to the next phase of the cycle. Failure to pass the checkpoints could lead to apoptosis or, if the cell is in G1, the transition to G0 phase, where the cell does not work towards replication.
b) A cell would stop replicating if DNA damage has not been repaired, or if any chromosomes during metaphase are not attached to microtubules
c) The type of signaling used for long-distance signals which can reach any cell type is endocrine signaling.
Great job! You would receive 2/3 points for this response. In order to gain your third point, you would need to explain endocrine signaling in more detail. Perhaps describe that hormones are most frequently the messengers for this type of signaling. Great work!
Student Sample 5
A) One cellular regulatory mechanism is quorom sensing in bacteria. The bacteria send out signals, and if there is too much of a concentration of these chemical signals, this prevents the bacteria from replicating further because the receptors on the bacteria can sense the concentration and send a signal to stop replication.
B) A cell may be given the signal to stop replicating if there are not enough resources in its environment to support the replication of the cell and maintain the functions of the cell or keep it alive.
C) Hormones are used for long distance signals and can reach any cell type. The steriod hormones, which are lipids/nonpolar molecules, can diffuse through the membrane of any cell, and elicit a response from the cell.
Great work on this response! You would receive a full 3/3 points. Remember that cells may also be given the signal to stop replicating if they are mutated. If this signal is not sent, overgrowth, such as cancer, may develop. Nice work!
Student Sample 6
a.) One cellular regulatory mechanism is the spindle checkpoint, which makes sure that the chromosomes are properly attached to the spindle microtubules in an orderly fashion. If all of them are not bound to the kinetochores correctly, the cell halts division until this is fixed and division can successfully happen.
b.) A cell could be given the signal to stop replicating if the cells around it are too densely packed. This is known as density-dependent inhibition, when cells are too crowded around each other and there is no real reason for more of them to be made. This makes sure there is not an unregulated growth of cells and that the cells do not waste energy, as it is important to conserve energy.
c.) Endocrine signaling is used for long-distance signals that can reach any type of cell. Different glands in the brain such as the pituitary and thyroid release these hormones in order to specify a function. These long-distance signals have the ability to reach every single cell in the body through the bloodstream and can bind to receptors only on cells that have the specific receptors for them. Then, they signal a response in the cell.
Great job on your answers here. You would receive 3/3 points! Your answer for part c is incredibly thorough and gives a great real life example to support the information provided. Nice work!
Common Correct Responses
For part a, there were a number of things that you could have included. Mentioning specific checkpoints in the cell cycle (G1, S, etc). You could also receive credit for mentioning cyclin-dependent kinases (CDK) and CDK-cyclin complexes, as they are the guards responsible for moving cells through the checkpoints. Another student mentioned quorum sensing in bacteria in which bacteria stop replicating when too many other cells are near them. This is a strong and unique example. Ensure you are using specific language when describing how the checkpoints work by mentioning WHY the cell would not be supposed to be replicating if it were to be inhibited.
For part b, there are any number of reasons why a cell may stop replicating. For most examples, individuals included some sort of mutation or error in replication or organelle division. You could also mention the example of quorum sensing from above or an error in spindle formation or connection.
For part c, hormone signaling is used for long distance signaling because hormone molecules do not break down quickly like other molecules might. These molecules are also often able to get through the plasma membrane, especially if it is a steroid hormone. They are able to enter all cells without the need for a specific receptor on the exteriror due to their hydrophobic nature.