Cell Communication and Signal Transduction AP Bio (Unit 4 A)

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?

• The proteins receive electrical signals from nerve cells.

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

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

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

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?

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

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

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

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

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?

• It involves the opening and closing of ion channels.

• It involves enzymes activating other enzymes.

• It involves changes in the expression of target genes.

• It involves protons moving down a concentration gradient.

Tags

NGSS.HS-LS1-3

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?

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

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

• Phosphorylase kinase catalyzes the hydrolysis of ATP.

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

Tags

NGSS.HS-LS1-3

Figure 1 shows a model of a signal transduction cascade, initiated by the binding of a ligand to the transmembrane receptor protein A. A DNA mutation changes the shape of the extracellular domain of transmembrane receptor protein A produced by the cell. Which of the following predictions is the most likely consequence of the mutation?

• Production of activated molecule 1 will stop, but production of activated molecules 2 and 3 will continue.

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

• The molecule that normally binds to protein A will not enter the cell, thus no cellular response will occur.

• Since protein A is embedded in the membrane, the mutation will be silent and not affect the cellular response.

Tags

NGSS.HS-LS1-1

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because

• only target cells retain the appropriate DNA segments.

• intracellular receptors are present only in target cells.

• only target cells have enzymes that break down aldosterone.

• only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes on.

When a signal transduction pathway involves a phosphorylation casade, what turns off the cell's response?

• a relay molecule that activates protein kinase 1

• protein kinase 2

• protein phosphatases

• active transcription factors