ap bio quiz 4.1-4.3 cell communication / signal..

Hormones are chemical signals that are released by cells in one part of the body that travel through the bloodstream to signal cells in another part of the body. Insulin is a hormone that is released by the pancreas that induces the uptake of glucose molecules from the bloodstream into cells. In this way, insulin lowers the overall blood glucose levels of the body. Osteoblasts and osteoclasts are two types of bone cells that play a role in regulating blood glucose levels (Figure 1).

Binding of insulin to the insulin receptor on osteoblasts activates a signaling pathway that results in osteoblasts releasing a molecule, OPG, that binds to neighboring osteoclasts. In response, the osteoclasts release protons (H+) and create an area of lower pH outside the cell. This low pHactivates osteocalcin, a protein secreted in an inactive form by osteoblasts.

The Esp gene encodes a protein that alters the structure of the insulin receptor on osteoblasts and interferes with the binding of insulin to the receptor. A researcher created a group of osteoblasts with an Esp mutation that prevented the production of a functional Esp product (mutant). The researcher then exposed the mutant strain and a normal strain that expresses Esp to glucose and compared the levels of insulin in the blood near the osteoblasts (Figure 2).

Based on the information provided, which of the following best justifies the claim that osteocalcin is a hormone?

A

The phosphorylation of the insulin receptor causes a response in osteoblast bone cells.

B

The osteoblasts in the bone secrete osteocalcin, which causes cells in the pancreas to change their activity.

C

The change in expression of Esp changes the insulin receptor activity of the osteoblast.

D

The activation of the osteocalcin by a bone cell is pH dependent.

B

The osteoblasts in the bone secrete osteocalcin, which causes cells in the pancreas to change their activity.

Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?

A

The proteins receive electrical signals from nerve cells.

B

The proteins leave the cell and travel in the bloodstream to other cells.

C

The proteins interact directly with proteins on the surfaces of other cells.

D

The proteins bind to molecules secreted by cells located in other parts of the body.

C

The proteins interact directly with proteins on the surfaces of other cells.

Notch is a receptor protein displayed on the surface of certain cells in developing fruit fly embryos. Notch's ligand is a membrane-bound protein called Delta that is displayed on the surface of adjacent cells. When Notch is activated by its ligand, the intracellular tail of the Notch protein becomes separated from the rest of the protein. This allows the intracellular tail to move to the cell's nucleus and alter the expression of specific genes.

Which of the following statements best explains Delta's role in regulating cell communication through the Notch signaling pathway?

A

Delta transmits a chemical signal to all the cells of a developing embryo.

B

Delta allows the cells of a developing embryo to communicate without making direct contact.

C

Delta restricts cell communication to short distances within a developing embryo.

D

Delta determines which cells in a developing embryo express the gene that encodes the Notch protein.

C

Delta restricts cell communication to short distances within a developing embryo.

In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?

A

Membrane-bound organelles

B

Condensed, duplicated chromosomes

C

Branched polysaccharides

D

Small, water-soluble molecules

D

Small, water-soluble molecules

A student claims that the Y chromosome contains the sex-determining region gene, known as the SRY gene, which causes male fetuses to develop testes.

Which of the following provides correct information about cell signaling that supports the claim?

A

The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues.

B

The SRY gene produces a protein that deletes portions of the X chromosome in males so that male characteristics can develop.

C

The SRY gene produces an RNA segment that is exported from specific cells and targets the developing gonads.

D

The SRY gene is found only in tissues of the developing gonads.

A

The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues.

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.

Which of the following statements best describes the role of cyclic AMP in the signal transduction pathway?

A

It acts as a signaling molecule that passes the signal from the cell to other cells.

B

It acts as a receptor that carries the signal from outside the cell to inside the cell.

C

It acts as a second messenger that helps relay and amplify the signal within the cell.

D

It acts as a channel protein that transmits the signal across the cell's nuclear membrane.

C

It acts as a second messenger that helps relay and amplify the signal within the cell.

The epinephrine signaling pathway plays a role in regulating glucose 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?

A

It involves the opening and closing of ion channels.

B

In involves enzymes activating other enzymes.

C

It involves changes in the expression of target genes.

D

It involves protons moving down a concentration gradient.

B

In involves enzymes activating other enzymes.

The epinephrine signaling pathway plays a role in regulating glucose 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.

Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?

A

It converts a polymer to its monomer subunits.

B

It moves substances across the plasma membrane.

C

It accelerates the production of a second messenger.

D

It transfers phosphate groups from ATP to protein substrates.

C

It accelerates the production of a second messenger.

The epinephrine signaling pathway plays a role in regulating glucose 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.

A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim?

A

Epinephrine is a signaling molecule that binds to a transmembrane protein.

B

The G protein in the epinephrine signaling pathway consists of three different subunits.

C

Phosphorylase kinase catalyzes the hydrolysis of ATP.

D

Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

D

Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

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?

A

Ethylene is a simple gaseous molecule, which makes it easily detected by receptors.

B

Fruit will ripen in closed containers without exposure to air.

C

Ethylene synthesis is under both positive and negative feedback regulation.

D

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

D

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

Two types of cells, alpha and beta cells, produce signaling molecules that affect blood sugar levels in opposite ways (Figure 1). Epinephrine is a chemical, often released during periods of exercise, that ultimately causes an increase in blood sugar levels in the body.

Based on Figure 1, which of the following best explains how exercise causes blood glucose levels to rise?

A

Epinephrine inhibits alpha cells, causing the release of glucagon, and activates beta cells, blocking the release of insulin.

B

Epinephrine activates alpha cells, blocking the release of glucagon, and inhibits beta cells, causing the release of insulin.

C

Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.

D

Epinephrine inhibits alpha cells, blocking the release of glucagon, and activates beta cells, causing the release of

C

Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.