AP Biology : Identify how molecules move into and out of cells

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Cytoplasmic Proteins

In which cellular compartment does glycolysis take place?

Possible Answers:

Intermembrane space

Inner mitochondrial membrane

Cytoplasm (Cytosol)

Mitochondrial matrix

Golgi apparatus

Correct answer:

Cytoplasm (Cytosol)

Explanation:

Glycolysis (the process of breaking down glucose) takes place in the cytoplasm, or cytosol—the aqueous portion of the cytoplasm. It is in the cytoplasm where the enzymes required for glycolysis are found.

The citric acid cycle takes place in the mitochondrial matrix, and the electron transport chain takes place along the inner mitochondrial membrane in order to pump protons into the intermembrane space.

Example Question #1 : Identify How Molecules Move Into And Out Of Cells

What is the function of a kinase?

Possible Answers:

Remove phosphates from ligands

Add ubiquitin to the ligand

Add phosphates to ligands

Change the structure of the ligand

Correct answer:

Add phosphates to ligands

Explanation:

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

A phosphatase removes a phosphate group from its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Example Question #41 : Cell Functions

What is the function of a phosphatase?

Possible Answers:

Change the structure of its ligand

Add an ubiquitin to its ligand

Remove a phosphate from its ligand

Add a phosphate to its ligand

Correct answer:

Remove a phosphate from its ligand

Explanation:

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Example Question #4 : Understanding Cytoplasmic Proteins

What is the function of an ubiquitin ligase?

Possible Answers:

Add a phosphate to its ligand

Remove a phosphate from its ligand

Add an ubiquitin to its ligand

Remove an ubiquitin from its ligand

Correct answer:

Add an ubiquitin to its ligand

Explanation:

Ubiquitin ligases add ubiquitin to their ligands. The addition of ubiquitin acts as a signal that a protein has become ineffective and is ready for degradation. When multiple ubiquitin residues have been added to a protein molecule, it is transported to the lysosome in the cell to be digested.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

Several different types of proteins can change the structure of a ligand, such as isomerases.

Example Question #1 : Understanding Types Of Cellular Communication

Immediately following synthesis, where are secretory proteins moved to?

Possible Answers:

Golgi body

Endoplasmic reticulum

The cytosol

The membrane

Vesicles

Correct answer:

Endoplasmic reticulum

Explanation:

When secretory proteins are synthesized they localize to the endoplasmic reticulum (ER), specifically the rough ER, for modification. Following modification there, secretory proteins are then packaged in secretory vesicles which go on to interact with the Golgi body, and are then finally released from the the plasma membrane.

Example Question #12 : Understanding Types Of Cellular Communication

Which of the following most accurately describes how a local cell signal is transmitted among nearby eukaryotic cells in animals?

Possible Answers:

Unspecified diffusion of signal proteins

Secretion of signaling molecules into the bloodstream

A pilus

Direct contact

Correct answer:

Direct contact

Explanation:

Local cell signaling in eukaryotic cells refers to the communication between nearby cells. This is done through direct contact between cells, namely via cell junctions and cell-cell recognition. Gap junctions are intercellular connections that allow cytoplasmic transfer in animal cells. The counterpart in plant cells is the plasmodesmata, which are channels penetrating the cell walls of cells, allowing communication. Cell-cell recognition is the ligand-receptor binding between two cells that elicits receptor cell response. Methods of local cell signaling allow nearby cells to communicate with each other and coordinate cellular responses and activities.

Example Question #483 : Cellular Biology

Which of the following choices most likely flows into the cell through open ion-gated receptors?

Possible Answers:

Genetic material 

Ions

The ligand that activated the channel

Large multi-subunit proteins

Correct answer:

Ions

Explanation:

As the name implies, when activated and induced to undergo a conformational change by a ligand, ions are able to flow through the channel and into the cell. This allows the charge across the membrane tobe manipulated by the cell. 

Example Question #1 : Identify How Molecules Move Into And Out Of Cells

Which of the following choices causes an ion-gated channel to deactivate and close?

Possible Answers:

Secondary messengers

Change in the membrane potential

Dissociation of ion channel kinases

Ligand dissociation

Correct answer:

Ligand dissociation

Explanation:

The binding of ligands causes the activation and conformational change in the ion channel to open it. Then, ions are able to flow into the cell. After a short time, the ligand dissociates from the ion gated channel. This causes the channel to deactivate and close. 

Example Question #2 : Identify How Molecules Move Into And Out Of Cells

Which of the following choices is not an an example of phagocytosis in multicellular organisms?

Possible Answers:

Uptake of dead cell material 

Uptake of foreign material

Endocytosis of solid nutrient particles into cells

Uptake of hormones

Correct answer:

Uptake of hormones

Explanation:

Phagocytosis is a form of endocytosis in which a cell takes up solid material through the invagination of the plasma membrane to form intracellular vesicles. In multicellular organisms, the process of phagocytosis is utilized in nutrient uptake, immune system response, and in cell recycling. Cells perform phagocytosis to uptake solid nutrients into the cell. The immune system uses phagocytosis to consume foreign material for eventual degradation. In the continual process of cell recycling, old and dead cell material is taken up and reused by cells.

Example Question #22 : Understanding Types Of Cellular Communication

In clathrin-mediated endocytosis, why does the rate of particle uptake decline quickly?

Possible Answers:

Lack of free ligands 

Binding of inhibitors

Negative feedback 

Internalization of receptors

Correct answer:

Internalization of receptors

Explanation:

In clathrin-mediated endocytosis, the binding of a specific ligand to a receptor triggers intracellular protein recruitment, which includes clathrin. These proteins stabilize the invagination and allow the clathrin pit to pull away from the plasma membrane. After it has separated from the membrane, the proteins and clathrin dissociate from the vesicle, which then fuses with an endosome. The invagination and vesicle formation from the plasma membrane includes the internalization of both the receptor and ligand. Over time the uptake by clathrin-mediated endocytosis decreases as the number of receptors on the cell’s surface. In other words, particle uptake declines due to the internalization of recptors as a result of clathrin-mediated endocytosis.

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