BIO CHAP 9

The process through which cells can detect and respond to signals in their extracellular environment is _____.

Cell communication

What do synaptic signaling and paracrine signaling have in common?

Cells release a signal that affects neighboring cells.

A G-protein coupled receptor associates with a G protein that contains how many subunits?

3

Insulin can activate lipid synthesis in adipose cells and block breakdown of glycogen in the liver. How could one hormone have different effects on different organs?

Adipose cells do not express the insulin receptor while liver cells do.

Some anti-cancer drugs block signal transduction pathways activated by growth factors. Which of the following would be a good target for such a drug?

An inhibitor of a protein kinase cascade.

What do enzyme-linked receptors and growth factor receptors have in common?

Both possess kinase activity when bound to a hormone.

During exposure to elevated glucose, a yeast cell will increase its uptake of glucose. Describe the mechanism by which the yeast sense the extracellular glucose.

By glucose binding to glucose receptors.

When receptors coupled to phospholipase C are activated, calcium levels in the cytosol increase when ______

IP3 binds to ligand-gated channels on the endoplasmic reticulum, releasing calcium.

You are testing a new chemotherapy drug that blocks a kinase in the cytoplasm that helps carry signals to the nucleus causing the cell to divide. If you expose cells to the drug at the same time you administer a hormone that should cause the cell to divide, the following steps would be blocked.

Receptor activation

Apoptosis is used in humans in order to eliminate cells infected by viruses, cells that are worn out, and those that have the potential to cause cancer.

TRUE

Hormones must bind a receptor to elicit a cell response, regardless of whether they operate locally or at long distances.

TRUE

If IP3 binds a Ca2+ ligand-gated ion channel in the endoplasmic reticulum then cytosolic Ca2+ levels will rise in the cell.

TRUE

In terms of cell signaling, estrogen in animal cells works in a similar fashion as the plant hormone auxin via binding to intracellular receptors.

TRUE

Ligands that promote cell death are typically found on the surface of cells of the immune system that recognize abnormal cells and target them for destruction.

TRUE

One common feature with G-protein coupled, enzyme-linked, and growth factor receptors is that their activation leads to activation of protein kinases.

TRUE

When insulin binds to it's G-protein coupled receptor (GPCR) what happens next?

The G protein loses GDP and gains GTP becoming activated.

Following its initial activation, how does a G protein become inactivated?

The G-protein a subunit GTP is hydrolyzed to GDP allowing reassociation of the G-protein a subunit and bg dimer.

Estrogen is a lipid soluble hormone that can easily cross membranes. Knowing this, what can be concluded about estrogen receptors?

The receptors would be found inside the cell.

Patients who have type 2 diabetes no longer respond normally to insulin. This symptom would be best explained by

Their cells express less insulin receptor.

What do G-protein coupled, enzyme-linked, and ligand-gated ion channel receptors have in common?

They change their conformation when bound to a hormone.

If you add the plant hormone auxin to one side of a plant the cells exposed to the auxin elongate. If you measured auxin levels in plant cells exposed to light what you would you expect to find?

They would be lower, causing the plant to bend towards the light.

Patients who have type 2 diabetes no longer express genes when exposed to insulin. How might this phenomenon be explained?

Transcription factors normally activated by insulin remain off.

A phosphatase is capable of dephosphorylating molecules. What would this enzyme do in a signal transduction pathway that used a kinase cascade?

Turn off the cascade.

Smooth muscle cells in the airways relax while those in the blood vessels contract in response to the hormone epinephrine. What would you expect to be different in these two types of cells exposed to epinephrine?

Types of proteins expressed.

When epinephrine binds to its G-protein linked receptor ____ is activated producing ___.

adenylyl cyclase, cAMP

A hormone binds a receptor and activates the cAMP signal transduction pathway ultimately leading to the cell response. If you wanted to develop a drug to block this pathway the drug would need to inhibit _____

adenylyl cyclase.

The production of second messengers in signal transduction offers at least two advantages, speed and

amplification.

Programmed cell death is known as ____.

apoptosis

When a cell secretes a growth factor that binds to receptors on its own membrane preventing it from proliferating this is an example of ____.

autocrine signaling

When cAMP is produced in a cell it will then ______.

bind to a repressor of protein kinase A

Phospholipase C hydrolyzes a membrane phospholipid to produce ____

both IP3 and diacylglycerol.

A key is placed into a keyhole then turned and the door opens. When considering the components of cell signaling, the action of turning the key would best correspond to

conformational change in the receptor once bound to the hormone

When epidermal growth factor binds to its _____________ the receptor phosphorylates itself, triggering a signal transduction pathway.

enzyme-linked receptor

If the concentration of a ligand is 100 times greater than the Kd of its receptor, _______ of the receptors will be bound to a ligand.

most

A substrate binding to an enzyme is most similar to a signal molecule binding to a

receptor.

In some cases, just a few hormone molecules binding to the surface of a cell can trigger a very large response because ____.

the signal is amplified by activation of enzymes that each catalyze multiple reactions

When a cell responds to a signal it sent this is an example of _____.

Autocrine signaling

Apoptosis through the extrinsic pathway is activated by factors such as lack of oxygen or growth factors.

FALSE

Auxin is a plant hormone that causes cells to shorten and allow plant growing tips to move toward the sun.

FALSE

Cyclic AMP activates protein kinase C in producing a cell response.

FALSE

G proteins and Ras are activated when bound to GDP.

FALSE

If epinephrine increases glycogen metabolism in muscle cells it would have the same function in brain cells.

FALSE

Epinephrine blocks the contraction of muscles in the airways. Which of the other activities of epinephrine is most likely to be regulated by the same type of pathway?

Inhibition of saliva production in salivary glands

When sodium ions move from one cardiac muscle cell to an adjacent cell causing them to contract in unison this is an example of ____.

direct intercellular signaling

When insulin is secreted from the pancreas and acts on muscle cells to increase glucose uptake this is an example of ____.

endocrine signaling

Hormones are released from one cells and act on other cells in distant organs and are thus an example of ____.

endocrine signaling that

When the concentration of a ligand is equal to the KD which of the following is true?

half of the receptors are bound to ligands.

Diabetics can be given the ____ insulin which binds to receptors on cells throughout the body increasing glucose uptake.

hormone

After being fed glucose a cell increases its intracellular glucose concentrations by _____ .

increasing membrane glucose transporters

IP3 binds to _____ receptors.

ligand-gated Ca2+ channel

When a neurotransmitter released from one neuron binds to a ______ on a second neuron, that neuron depolarizes and fires.

ligand-gated ion channel

When a cell secretes a growth factor that binds to receptors on neighboring cells causing them to proliferate this is an example of ____.

paracrine signaling

When a cell secretes a growth factor that binds to receptors on neighboring cells causing them to proliferate this is an example of _____.

paracrine signaling

The molecule directly responsible for breaking down cAMP to inactive AMP is

phosphodiesterase

Adenylyl cyclase is to cAMP as ________ is to IP3.

phospholipase C

After estrogen binds to receptors, these estrogen receptors gain ______ activity.

transcription factor