Chapter 11

Question 1

What is quorum sensing?

Answer 1

Concentration of signaling molecules allows bacteria to sense local population density

Question 2

What is biofilm?

Answer 2

An aggregation of bacterial cells adhered to a surface

Question 3

Types of local signaling

Answer 3

Paracrine signaling ; synaptic signaling

Question 4

Paracrine signaling

Answer 4

Animal cells communicate using secreted messenger molecules that travel only short distances

Question 5

Synaptic signaling

Answer 5

Occurs in the animal nervous system when a neurotransmitter is released in response to an electric signal

Question 6

Long-distance signaling

Answer 6

Used hormones ; endocrine signaling (bloodstream)

Question 7

Three stages of cell signaling

Answer 7

Signal reception, signal transduction, cellular response

Question 8

Signal reception

Answer 8

Binding of ligand (signaling molecule) and receptor

Question 9

Cell surface receptors

Answer 9

Membrane receptors located on cell surface ; heir large or polar ligands can’t diffuse through the membrane

Question 10

Intracellular receptor

Answer 10

Located inside cell ; their ligands are small or nonpolar and can diffuse across the membrane

Question 11

GPCRs

Answer 11

G Protein-coupled receptors

Question 12

RTKs

Answer 12

Receptor tyrosine kinases

Question 13

Receptor tyrosine kinases

Answer 13

Membrane receptors that transfer phosphate groups from ATP to another protein

Question 14

Ion channel receptors (ligand-gates)

Answer 14

Contain a region that can act as a gate, opening or closing the channel, when the receptor changes shape

Question 15

Intracellular receptors

Answer 15

Receptor proteins found in cytoplasm or nucleus

Question 16

What can activated hormone-receptor complexes do?

Answer 16

They can act as a transcription factor, turning on or off specific genes

Question 17

What is phosphorylation?

Answer 17

Protein kinases transfers phosphates from ATP to protein

Question 18

Examples of second messengers

Answer 18

Cyclic AMP and Ca 2+ (spread by diffusion)

Question 19

What does adenylyl cyclase do?

Answer 19

Converts ATP to cAMP in response to an extracellular signal

Question 20

What does cAMP do?

Answer 20

Activates protein kinase A which then phosphorylates various other proteins

Question 21

What does adenylyl cyclase do?

Answer 21

Makes cAMP from ATP

Question 22

What happens in cholera bacterium?

Answer 22

Vibrio cholerae produces a toxin that modifies G proteins so that it is stuck in its active form ; leads to continuous production of cAMP, causing intestinal cells to secrete lots of salt which is fallowed by water ; untreated the person can die

Question 23

Why is Ca 2+ a good second messenger?

Answer 23

It’s concentration in the cytosol is normally much lower than the concentration outside the cells and in certain organelles within the cell ; small change in # represents larger % change

Question 24

IP3 & DAG and where they are produced

Answer 24

Inositol triphosphate & diacylglycerol ; produced by cleavage of a certain kind of phospholipid in the plasma membrane

Question 25

4 aspects of signal regulation

Answer 25

Amplification of signal, specificity of response, overall efficiency of response, termination of signal

Question 26

What happens in Signal amplification?

Answer 26

At each step the number of activated products can be greater than the proceeding step

Question 27

What is specificity of cell signaling?

Answer 27

Proteins allow cells to detect and respond to different signals ; same signal can have different effects with different proteins

Question 28

What is a scaffolding protein?

Answer 28

Large relay protein to which several other relay proteins are attached ; increase efficiency by grouping together different proteins involved in same pathway

Question 29

4 ways to shut off signal

Answer 29

Ligand unbinds from receptor ; ligand/receptor complex is internalized and degrades ; second messengers are degraded ; protein phosphates remove phosphate off previously phosphorylated proteins