Cells with inactive GSK3β fail to trigger apoptosis.

Cells with inactive GSK3β fail to proceed past the G2/M checkpoint.

Cells with overactive GSK3β are more likely to repair DNA damage.

Cells with overactive GSK3β have longer cell cycles.

Homologous chromosomes pair.

Replicated chromosomes line up on the equatorial plate.

Tetrads form.

Unreplicated chromosomes become oriented in the center of the cell.

A receptor mutation results in activation of a cell-division pathway in the absence of the appropriate ligand.

A mutation results in the loss of the ability to produce a tumor-suppressor protein.

A defect in a cell-cycle checkpoint prevents a cell from entering the S phase.

At the anaphase checkpoint, separation of chromatids occurs without all centromeres being attached to kinetochore microtubules from both poles.

Homologous chromosomes (each with two sister chromatids) will move toward opposite poles of the cell.

Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

The nuclear envelope will break down, and the spindle will begin to form.

The chromatin will decondense, and the daughter cell will enter interphase.

kinetochores in the mitotic cell

a spindle in the mitotic cell

twice as many chromosomes in the meiotic cell

paired homologous chromosomes in the meiotic cell

During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin.

After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels.

At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual’s rate of respiration to compensate for the difference.

A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcription factor required for expression.

Activated platelets release chemicals that inhibit blood clot formation.

Activated platelets release signaling molecules that inhibit cell division in damaged tissue.

Activated platelets constrict the blood vessels, stopping blood flow.

Activated platelets release chemicals that activate more platelets.

As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.

As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine.

As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine.

As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.

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.

Increased activation of the immune system

Increased urine production by the kidneys

Increased bone and collagen formation

Increased mobilization of fatty acids from fat cells

The molecules are actively transported by motor proteins along the cytoskeleton.

The molecules pass freely through plasmodesmata, which are cytoplasmic strands connecting two cells.

The molecules are swept along in the extracellular fluid by cilia projecting from cell membranes.

The molecules bind reversibly to receptors on the cell membranes of xylem.

It speeds up the transmission of impulses by acting as an electrical insulator.

It speeds up the transmission of impulses by integrating signal information more quickly.

It slows down the transmission of impulses by forming gaps of unsheathed axons.

It slows down the transmission of impulses by impeding the movement of ions across the neuronal membrane.

The action potential jumps from one axon to the next connecting axon.

The action potential travels through the synapse to the next connecting dendrite.

The action potential jumps the synapse to the next connecting dendrite.

The action potential causes a release of neurotransmitters that travel across the synapse.

exchange of electrons between specialized proteins embedded in the plasma membrane of the sensory neuron to the plasma membrane of the interneuron

release of chemical messengers into the space between the axon of the sensory neuron and the plasma membrane of the interneuron

transfer of a phosphate group from ATP in the sensory neuron to a protein substrate in the interneuron

flow of protons down an electrochemical gradient through a gated channel between the sensory neuron and the interneuron

Membrane-bound organelles

Condensed, duplicated chromosomes

Branched polysaccharides

Small, water-soluble molecules

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 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.

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.

ADH promotes an increase in the movement of sodium into the bloodstream.

ADH promotes an increase in the movement of water into the bloodstream.

ADH promotes an increase in the excretion of water from the body.

ADH promotes an increase in the secretion of additional ADH from the pituitary gland.

It converts a polymer to its monomer subunits.

It moves substances across the plasma membrane.

It accelerates the production of a second messenger.

It transfers phosphate groups from ATP

ATP to protein substrates.