The figure above shows a model of a ligand precursor being cleaved to produce an active ligand that binds to a specific receptor. Which of the following is most likely to reduce the binding of the active ligand to its receptor?

• A change in the cytoskeletal attachment of transmembrane proteins

• The presence of a large amount of the precursor form of the ligand

• An increase in the ratio of the number of unsaturated to the number of saturated fatty acid tails of the membrane lipids

• A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?

• Cell signaling uses the highest molecular weight molecules found in living cells.

• Cell signaling has largely been replaced by other cell functions in higher mammals.

• Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

• Cell signaling functions mainly during early developmental stages.

Tags

NGSS.HS-LS4-1

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

• Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP

  .

• Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of glycogen to glucose.

• Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol.

• Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the endocytotic vesicle.

The vertebrate forelimb initially develops in the embryo as a solid mass of tissue. As development progresses, the solid mass near the end of the forelimb is remodeled into individual digits. Which of the following best explains the role of apoptosis in remodeling of the forelimb?

• Apoptosis replaces old cells with new ones that are less likely to contain mutations.

• Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells.

• Apoptosis involves the destruction of extra cells in the developing forelimb, which provides nutrients for phagocytic cells.

• Apoptosis in the developing forelimb triggers the differentiation of cells whose fate was not already determined.

An example of juxtacrine(direct) cell communication is:

• White blood cells bumping into each other sharing antigen info

• Neurons communicating across a synapse

• Hormones traveling through the blood stream to target tissues

An example of paracrine (local) cell communication is:

• White blood cells bumping into each other sharing antigen info

• Neurons communicating across a synapse

• Hormones traveling through the blood stream to target tissues

A signal molecule that binds to a plasma-membrane protein is a

• ligand
• second messenger
• protein kinase
• receptor protein

What determines whether a cell is a target cell for a particular signal molecule?

• phosphorylation cascade
• cAMP
• signal receptors
• phosphatase

What determines whether a signal molecule binds on the surface or enters the cell?

• size
• polarity
• ability to cross the membrane
• all of these are correct

A cell converting a chemical signal into a cellular response is known as __.

• energetics

• transduction

• ligand response

• transformation