Question 1

A mutation in the DNA binding domain of a steroid hormone receptor is most likely to affect the

Accepted Answer

A) conformational change of the receptor. 
B) binding of the hormone to the receptor. 
C) translocation of the receptor to the nucleus. 
D) cellular response to the hormone.

Question 2

In plants,cell-cell junctions can only occur at gaps in the cell walls through cytoplasmic connections that form across the plasma membranes of the touching cells.These junctions are called

Accepted Answer

A) desmosomes. 
B) tight junctions. 
C) plasmodesmata. 
D) the cellulose matrix. 
E) adhering junctions.

Question 3

Synaptic signaling requires which of the following to be released into the synaptic gap?

Accepted Answer

A) hormones 
B) internal receptors 
C) genes 
D) neurotransmitters 
E) lipids

Question 4

Chemically-gated ion channels are receptor proteins through which ions pass.A cell biologist has blocked these channels in a lab rat's liver tissue by using a chemical that

Accepted Answer

A) prohibits binding of a signal molecule. 
B) prohibits ions from entering the cell via active transport. 
C) causes ions to move in the opposite direction of the ion gradient. 
D) prohibits second messenger signaling.

Question 5

Hormones are an example of intercellular communication known as _____________ signaling.

Accepted Answer

A) neural 
B) endocrine 
C) paracrine 
D) autocrine

Question 6

A mutation that affects Ca++ binding to calmodulin is most likely to interfere with which aspect of a signal transduction pathway?

Accepted Answer

A) the flow of Ca++ ions through ion channel receptors 
B) the cellular response to the second messenger 
C) MAP kinase cascade 
D) G protein activity

Question 7

Signals with short-lived,local effects are called

Accepted Answer

A) direct contact. 
B) endocrine signals. 
C) paracrine signals. 
D) synaptic signals. 
E) light signals.

Question 8

In the digestive tract adjacent cells develop connections to form a sheet that prevents leakage of small molecules.These connections between cells are called

Accepted Answer

A) communicating junctions. 
B) desmosomes. 
C) gap junctions. 
D) ion gates. 
E) tight junctions.

Question 9

All of the following statements about chemically-gated ion channels are true except

Accepted Answer

A) their amino acid chains wind back and forth across the membrane. 
B) they close in response to binding of the signal molecule. 
C) a pore exists in the center of the protein. 
D) the pore connects the extracellular fluid with the cytoplasm. 
E) the pore is big enough for ions to pass through it.

Question 10

A researcher is investigating several MHC proteins.That means she is

Accepted Answer

A) studying proteins similar to G-protein-coupled receptors. 
B) studying proteins that provide surface markers for distinguishing between "self" and "non-self" cells. 
C) studying proteins that are commonly used to detect human blood groups (A,B,AB,and O). 
D) studying proteins that act as second messengers.

Question 11

Tight and anchoring _______ cause cells to adhere tightly to each other.

Accepted Answer

A) cells 
B) proteins 
C) signals 
D) junctions

Question 12

The protein SOS is a guanine nucleotide exchange factor for Ras.SOS helps facilitate the exchange of GDP for GTP.What would be the effect of a mutation that inhibits the interaction between SOS and Ras?

Accepted Answer

A) GTP would remain bound to Ras,thereby disrupting downstream signaling events. 
B) GDP would remain bound to Ras,thereby disrupting downstream signaling events. 
C) GTP would remain bound to Ras,leading to overstimulation of the Ras pathway. 
D) GDP would remain bound to Ras,leading to overstimulation of the Ras pathway.

Question 13

Communication between cells can occur by all of the following basic mechanisms except

Accepted Answer

A) direct contact. 
B) intracellular signaling. 
C) paracrine signaling. 
D) endocrine signaling. 
E) synaptic signaling.

Question 14

The molecules that convert extracellular signals into intracellular ones are

Accepted Answer

A) neurotransmitters. 
B) peptide hormones. 
C) cell surface receptors. 
D) growth factor proteins. 
E) genes.

Question 15

Leptin is a hormone that is produced by fat cells and plays a role in body metabolism and obesity.Studies have demonstrated that when obese mice are injected with leptin they quickly lose their excess weight.Interestingly,however,many overweight people have high levels of leptin in their bloodstream.Which of the following explanations is most consistent with this observation?

Accepted Answer

A) Paracrine signaling may be disrupted in obese people with high levels of leptin. 
B) Obese people who have high levels of leptin may have a defective leptin receptor. 
C) The form of leptin released by obese people may lack protein kinase activity. 
D) In obese people with high levels of leptin,the leptin is binding to the wrong receptor.

Question 16

Short-lived,causing local effects.

Accepted Answer

A) paracrine signaling 
B) direct contact 
C) endocrine signaling 
D) synaptic signaling

Question 17

The protein Sonic Hedgehog (SHH)plays a role in specifying the identity of digits (such as fingers,etc. )in mammals.Several digits arise directly from cells that both express and respond to secreted SHH.In this case,SHH is acting as

Accepted Answer

A) a direct contact signal. 
B) an endocrine signal. 
C) a paracrine signal. 
D) an autocrine signal.

Question 18

A biochemist is designing a new drug that will mimic the shape and function of a particular signal molecule.Therefore she must produce a molecule that will bind to the receptor protein and

Accepted Answer

A) induce a change in the receptor molecule shape,which will ultimately prevent a cellular response. 
B) induce a change in the receptor molecule shape,which will ultimately produce a cellular response. 
C) induce a change in the phospholipid bilayer that causes a polar reversal allowing the molecules to be endocytosed. 
D) produce a cellular response by altering the Na+/K+ pump located near the receptor site.

Question 19

Which of the following is not part of the cell communication system in animal cells?

Accepted Answer

A) gap junctions 
B) plasmodesmata 
C) tight junctions 
D) desmosomes

Question 20

Chemically-gated ion ________ open or close when signal molecules bind to the channel,allowing specific ions to diffuse through the channel.

Accepted Answer

A) channels 
B) molecules 
C) species 
D) membranes

Exam 9: Cell Communication