Cell Communication

Question 1

Cells in a multicellular organism communicate by __________ ___________.

Answer 1

chemical messengers

Question 2

How might animal cells communicate in local signaling

Answer 2

direct contact, or cell-cell recognition

Question 3

Describe local regulators

Answer 3

messenger molecules that travel short distances

Question 4

Describe paracrine signaling

Answer 4

local regulator released directly onto one cell by another

Question 5

Describe synaptic signaling

Answer 5

a nerve signal triggers the release of a local regulator onto a near by cell

Question 6

What are hormones?

Answer 6

chemical messengers that travel long distance

Question 7

Describe signal transduction pathway

Answer 7

a set of step that trigger a certain response from a cell after a signal is received

Question 8

What are the 3 steps of signal transduction pathway

Answer 8

1. Reception
2. Transduction
3. Response

Question 9

What is reception

Answer 9

delivery of a signal to a cell

Question 10

What are ligands

Answer 10

Signal molecules

Question 11

How to certain ligands go through the cell membranes?

Answer 11

Water soluble ligands must bind to receptor proteins in the cell membrane
Non-polar or small ligands can travel directly in the cell

Question 12

What is a G protein-coupled receptor

Answer 12

membrane receptor that activates a G protein when a ligand is present

Question 13

What process do G protein-coupled receptors start

Answer 13

transduction

Question 14

How does a G protein work?

Answer 14

when activated, it uses energy from GDP becoming GTP to turn on an enzyme

Question 15

Describe receptor tyrosine kinase

Answer 15

membrane receptors that attach phosphates to tyrosines.

Question 16

How is a dimer made

Answer 16

When the ligand is present, the two kinases form

Question 17

What does a dimer do

Answer 17

trigger multiple transduction pathways

Question 18

Describe a ligand-gated ion channel

Answer 18

receptor opens like a gate when a ligand is present to allow ions in

Question 19

Small or hydrophobic ligands go inside a cell how?

Answer 19

they travel directly through the cell membrane

Question 20

What is a hormone receptor complex

Answer 20

a ligand and internal receptor binded together

Question 21

What process does a hormone receptor complex start?

Answer 21

transduction

Question 22

Signal transduction usually involves multiple steps that includes what to get a response from a cell?

Answer 22

turning a sequence of proteins on and off

Question 23

What is phosphorylation

Answer 23

adding a phosphate (turns proteins on)

Question 24

What is dephosphorylation

Answer 24

removing a phosphate (turns proteins off)

Question 25

Phosphorylation is done by what types of proteins?

Answer 25

Protein kinases

Question 26

Dephosphorylation is done by what types of proteins?

Answer 26

Protein phosphatases

Question 27

Describe second messengers

Answer 27

Small, water soluble molecules or ions, which rapidly relay the signal from the membrane-receptor-bound "first messenger" into a cell's interior

Question 28

What are types of second messengers?

Answer 28

cAMP (made from ATP), IP3, Ca+, DAG

Question 29

Cell usually respond by doing what?

Answer 29

synthesizing enzymes or proteins, or turning genes on or off

Question 30

What is apoptosis?

Answer 30

A response that is a programmed or controlled cell suicide

Question 31

How does apoptosis work?

Answer 31

A cell is chopped and packaged into vesicles that are digested to prevent enzymes from leaking out and damaging other cells

Question 32

Apoptosis can be triggered by:

Answer 32

An extracellular death-signaling ligand DNA damage in the nucleus Protein misfolding in the endoplasmic reticulum

Question 33

List two advantages of a multistep pathway in the transduction stage of cell signaling

Answer 33

1. amplification to produce a large cellular response and also provide opportunity for regulation and coordination. 2. easier to regulate or shut off the system since there are more targets.

Question 34

Explain how an original signal molecule can produce a cellular response when it may not even enter the target cell

Answer 34

The signal molecule binds a receptor on the surface of the cell. This receptor is embedded in the cell membrane. Upon binding of a signal molecule the receptor will become active and will be able to activate proteins in the cytoplasm. This in turn will affect other proteins eventually resulting in a cell response.

Question 35

Explain how signals can be sent through direct contact

Answer 35

They may be communicated between cells through direct cytoplasmic connections (gap junctions or plasmodesmata) or through contact of surface molecules (cell-cell recognition in animal cells).

Question 36

How do second messengers function in signal transduction pathways

Answer 36

Second messengers participate in pathways initiated by both G protein-coupled receptors and receptor tyrosine kinases. Commonly used second messengers are cAMP and calcium ions.

Question 37

Explain why different types of cells may respond differently to the same signal molecule

Answer 37

each type of cell has its own complement of proteins