AP Biology Unit 4 Test

Mutations in genes like p53 can cause interfeRie in cell signaling pathways and lead to cancer. Which of the following statements BEST predicts the effect of a mutation in the p53 gene?

A mutation in the p53 gene results in the transcription of a non- functioning tumor suppressor protein.

motor proteins

A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.

Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism?

Activated platelets release chemicals that activate more platelets.

During labor and delivery, contractions begin and continue through positive feedback. Unlike negative feedback, in positive feedback, a stimulus increases a response. In turn, the response reinforces the release of a chemical signal that increases the physiological response. Based on the figure, which of the following MOST likely disrupts the positive feedback loop that results in contractions?

Expulsion of the baby causes cessation of oxytocin secretion from the pituitary gland.

The epinephrine signaling pathway plays a role in regulating giucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway?

It involves enzymes activating other enzymes.

In cell communication, some signaling molecules bind to membrane receptors, while others can pass through the cell membrane into the cytoplasm without assistance. Once the signaling molecule attaches with a receptor, signal transduction takes place. Which of the following MOST correctly describes the difference between types of signaling molecules?

Local regulators affect change in nearby cells once they bind with receptors. Hormones affect change in cells that are not alwaus in the same location as the signaling cell.

Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening. Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit?

Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

The cell cycle is marked by a series of checkpoints that determine if and when a cell will proceed to the next phase. These phases ure tightly regulated by chemical signals, and the timing varies from one cell type to the next. The table below gives sample data from a collection of cells based on the number of cells found in each phase of the cell cycle.

Neurological tissue

A DNA mutation changes the shape of the extracellular domain of transmembrane receptor protein produced by the cell. Which of the following predictions is the most likely consequence of the mutation?

The molecule that normally binds to protein A will no longer attach, deactivating the cellular response.

Intracellular responses are directed by changes within the cell or by changes in the extracellular space. Which of the following statements BEST confirms the claim that specific cellular responses come from external environmental cues?

The removal of a hormone signal from the extracellular space prompts secondary messenger breakdown.

Intracellular or extracellular triggers can initiate apoptosis signals. During apoptosis, a message prompts a cascade of proteins. Part of programmed cell death involves the fragmentation of DNA and the deconstruction of organelles and other cytoplasmic components. Apoptosis shields adjacent cells from potential damage. Which of the following is an example of apoptosis that aids in embryonic development?

Unnecessary tissues undergo apoptosis for organ sculpting

kinetochore

a complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach.

Reception, transduction, and response are the three stages of cell communication. Many biological processes rely on molecules like cyclic AMP (cAMP), a derivative of ATP, for intracellular signal transduction. Based on the figure, which of the following BEST describes the role of cAMP in the signal transduction pathway?

cAMP is a hormone that crosses the cell membrane and initiates the signal transduction pathway.

actin filaments

protein fibers that play a role in cell division and shape

The lipid-soluble hormone aldosterone initiates transcription of genes associated with the regulation of sodium and water. When aldosterone traverses the cell membrane, only target cells are affected by its presence. Which of the following BEST explains the reason aldosterone only affects the intracellular environment of target cells?

Aldosterone binds with intracellular receptors that are only present in target cells.

The hypothalamus helps balance body temperature through thermoregulation via cell signaling. The chemical signals from the hypothalamus elicit a physiological response in blood vessels to maintain homeostasis. Based on the figure, which of the following statements BEST explains how negative feedback works to maintain homeostasis when there are changes in the external temperature?

As body temperature increases, the blood vessels dilate, and blood flow to skin increases.

Cell signaling ellits a varlety of responses, from modification of gene expression resulting in altered phenotypes to programmed cell death. Cell signaling occurs in both plant and animal cells. In animal cells, cytokines regulate the expresslon of genes through signal transduction. Ethylene gas affects enzymes and initlates a signal transduction pathway that causes frult ripening.

Different cells have different receptors that can bind with specific ligands, Relay molecules act like molecular switches for varlous signaling pathways.

Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening?

Ethulene gas is a chemical signal through which ripening fruits tridger the ripening process in other fruits.

Cell communication is a step-by-step process that réquires the cell to be fully integrated. This process is known as the signal transduction pathway. This three-part system allows cells to communicate not only with each other but internally to help regulate all reactions. Suppose a peptide hormone that acts as a ligand for other cells is being improperly made.

Reception. If the peptide hormone is not correctly made, then it is unlikely to be able to bind with the receptor molecule.

Microtubules

Spiral strands of protein molecules that form a tubelike structure

Amount of DNA per cell during different stages of the cell cycle, relative to the beginning of the G1 stage. Which of the following best describes how the amount of DNA in the cell changes during M phase?

The amount of DNA is halved as the cell divides into two daughter cells

Cell signals regulate the progression of the cell cycle at three checkpoints- G1,G2, and M phases. Regulatory proteins, like cyclins, control the cell cycle by activating or inactivating other proteins via phosphorylation. Progression through the cell cycle is dependent on whether the cell can pass checkpoints in the G1, G2 and M phases. When a cell does not meet checkpoint requirements, it exits the cell cycle and enters a nondividing phase called GO. Which of the following statements is MOST likely the cause for a cell exiting the cell cycle and entering GO?

The cell enters GO for a period of quiescence before returning to the cell cycle for dividing.

The cell cycle is tightly regulated by a series of chemicals known as cyclins and cyclin-dependent kinases (CDKs). When these cyclins and CDKs are mutated, they are no longer able to properly exact control over the cell. The table below shows the various cyclins and CDKs along with the phases they influence. Certain strains of the herpes virus mutate the function of CDK6.

The cell will continue through to mitosis, causing an increase in cell division. Leading to tumor development.