Cell Communication (1)

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

• hormonal signaling

• autocrine signaling

• paracrine signaling

• endocrine signaling

• synaptic signaling

In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following?

• The growth factor is a paracrine signal.

• The growth factor depends on osmosis.

• The mammal only carries growth factor through the lymph.

• The growth factor is an exocrine signal.

• The growth factor is an endocrine signal.

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

• receptor

• relay molecule

• transducer

• signal molecule

• endocrine molecule

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

• the active site of an allosteric enzyme that binds to a specific substrate.

• tRNA specifying which amino acids are in a polypeptide.

• a metabolic pathway operating within a specific organelle.

• an enzyme having an optimum pH and temperature for activity.

• an antibody in the immune system.

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP?

• It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

• It could activate only the epinephrine system.

• It would be able to carry out reception and transduction but would not be able to respond to a signal.

• It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

• It would employ a transduction pathway directly from an external messenger.

Testosterone functions inside a cell by

• acting as a signal receptor that activates tyrosine kinases.

• binding with a receptor protein that enters the nucleus and activates specific genes.

• acting as a steroid signal receptor that activates ion channel proteins.

• becoming a second messenger that inhibits adenylyl cyclase.

• coordinating a phosphorylation cascade that increases spermatogenesis.

Which of the following is true of transcription factors?

• They regulate the synthesis of DNA in response to a signal.

• They transcribe ATP into cAMP.

• They initiate the epinephrine response in animal cells.

• They control gene expression.

• They regulate the synthesis of lipids in the cytoplasm.

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

• G protein-coupled receptors

• ligand-gated ion channels

• steroid receptors

• receptor tyrosine kinases

• none of the above

Because most receptors are membrane proteins, which of the following is usually true?

• They lead to changes in intracellular ion concentration.

• They open and close in response to protein signals.

• They are only attached to one membrane surface: exterior or interior.

• They preferentially bind with lipid or glycolipid signal molecules.

• They change their conformation after binding with signal polypeptides.

Since steroid receptors are located intracellularly, which of the following is true?

• The receptor molecules are themselves lipids or glycolipids.

• The steroid/receptor complex can cross the nuclear membrane.

• The unbound steroid receptors are quickly recycled by lysosomes.

• The concentration of steroid receptors must be relatively high in most cells.

• The receptor molecules are free to move in and out of most organelles.