Concept 5.6

When protein membrane receptors are activated, what usually happens?

• A change occurs in intracellular ion concentration.

• The receptors open and close in response to protein signals.

• A change occurs on only one membrane surface: exterior or interior.

• The receptor preferentially binds with lipid or glycolipid signal molecules

• The receptor changes conformation after binding with signal polypeptides.

Which of the following is true of steroid receptors?

• The receptor molecules are themselves lipids or glycolipids.

• The receptor may be inside the nuclear membrane.

• The unbound steroid receptors are quickly recycled by lysosomes.

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

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

• They might compensate by receiving nutrients via a factor.

• They could develop normally in response to neurotransmitters instead.

• They could divide but never reach full size.

• They might not be able to multiply in response to growth factors from nearby cells.

• Hormones would not be able to interact with target cells.

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

• paracrine signaling

• endocrine signaling

• autocrine signaling

• synaptic signaling

In which of the following ways do plant hormones differ from hormones in animals?

• Plant hormones interact primarily with intracellular receptors.

• Plant hormones may travel in air or through vascular systems.

• Animal hormones are found in much greater concentration.

• Plant hormones are synthesized from two or more distinct molecules

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

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 nitric oxide

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.

In general, a signal transmitted via phosphorylation of a series of proteins

• brings a conformational change to each protein.

• requires binding of a hormone to a cytosol receptor.

• cannot occur in yeasts because they lack protein phosphatases.

• requires phosphorylase activity.

Which of the following most likely would be an immediate result of a growth factor binding to its receptor?

• protein kinase activity

• adenylyl cyclase activity

• GTPase activity

• protein phosphatase activity