Cell Communication

Question 1

Cell-to cell communication importance

Answer 1

Critical for the function and survival of cells. Responsible for the growth and development of multicellular organisms

Question 2

Three ways cells communicate

Answer 2

1. Direct contact
2. Local signaling
3. Long-distance signaling

Question 3

Direct contact

Answer 3

Communication through cell junctions, signaling substances and other material in the cytoplasm can pass freely between adjacent cells
Animal cells: Gap junctions
Plant cells: Plasmodesmata

Question 4

Local regulators/signaling

Answer 4

1. Secreting cell releases chemical messages that travel a short distance through the extracellular fluid
2. Chemical messages will cause a response in a target cell

Question 5

Paracrine signaling

Answer 5

Secretory cells release local regulators (growth factors) via exocytosis to an adjacent cell

Question 6

Synaptic signaling

Answer 6

Occurs in animal nervous systems
1. Neurons secrete neurotransmitters
2. Diffuse across the synaptic cleft-space between the nerve and target cell

Question 7

Long Distance signaling

Answer 7

-Animals and plants use hormones for this type of signaling
Plants: Release hormones that travel in the plants (xylem or phloem) or through the air to reach target tissues
Animals: Endocrine signaling. Specialized cells release hormones into the circulatory system where they reach target cells

Question 8

Insulin as an example of endocrine signaling

Answer 8

Released from the pancreas into the bloodstream where it circulates through the body and binds to target cells

Question 9

Cell messaging three stages

Answer 9

1. Reception
2. Transduction
3. Response

Question 10

Reception Overview

Answer 10

The detection and receiving of a ligand by a receptor in a target cell

Question 11

Receptor definition

Answer 11

Macromolecule that binds to a signal molecule (ligand)

Question 12

Receptor interaction

Answer 12

• All receptors have an area that interacts with the ligand and an area that transmits a signal to another protein
  *Binding between ligand and receptor is highly specific

Question 13

Steps of reception

Answer 13

1. When the ligand binds to the receptor, the receptor activates via a conformational change
2. This allows the receptor to initiate a transduction signal

Question 14

Ligand

Answer 14

Molecule that binds to another (usually larger) molecule

Question 15

Where are receptors located?

Answer 15

Plasma membrane or intracellular

Question 16

Plasma membrane receptors

Answer 16

-Most common type of receptor
-Binds to receptors that are polar(water soluble, large)
Examples: G protein coupled receptors, ligand-gated ion channels

Question 17

Intracellular receptors

Answer 17

-Found in cytoplasm or nucleus of target cell
-Binds to ligands that can pass through the plasma membrane (hydrophobic molecules, steroid and thyroid hormones, gasses like nitric oxide)

Question 18

Transduction overview

Answer 18

The conversion of an extracellular signal to an intracellular signal that will bring about a cellular response

Question 19

What does transduction require?

Answer 19

A sequence of changes in a series of molecules known as the signal transduction pathway

Question 20

Signal transduction pathway and protein activity

Answer 20

Regulates protein activity through phosphorylation and dephosphorylation

Question 21

Kinase

Answer 21

Phosphorylation, turns on the process, relays signal inside cell

Question 22

Phosphotase

Answer 22

Dephosphorylation, shuts off pathways

Question 23

During transduction a signal is…

Answer 23

Amplified

Question 24

Second messengers

Answer 24

Small, non-protein molecules help relay the message and amplify the message and response.
*Cyclic AMP common 2nd messenger

Question 25

Response overview

Answer 25

The final molecule in the signaling pathway converts the signal to a response that will alter a cellular process

Question 26

Three examples of responses:

Answer 26

1. Protein that can alter membrane permeability
2. Enzyme that will change a metabolic process
3. Protein that turns genes on or off

Question 27

Signal transduction pathways

Answer 27

*Can influence how a cell responds to it’s environment
*Can result in changes in gene expression and cell function, alter phenotypes or result in cell death

Question 28

Changes in signal transduction pathways

Answer 28

-mutations to receptor or to any component of the signaling pathway will result in a change to the transduction of the signal

Question 29

Two categories of cell membrane receptors

Answer 29

1.G protein coupled receptors (GPCR’s)
2. Ion channels

Question 30

G protein coupled receptors overview

Answer 30

-Largest category of cell surface receptors
-Important in animal sensory systems
-Binds to a G protein, GTP, which is an energy molecule similar to ATP
-The GPCR, enzyme, and G protein are inactive until a ligand binds to GPCR on the extracellular side

Question 31

What does ligand bonding cause in GPCR’s

Answer 31

1. Causes cytoplasmic side to change shape
2. Allows for the G protein to bind to GPCR
   *Activates the GPCR and G protein
   *GDP becomes GTP
3. Part of the activated G protein can then bind to the enzyme
   *Activate enzyme, amplifies signal and leads to a cellular response

Question 32

Ion channels location and importance

Answer 32

1. Plasma membrane
2. Important in the nervous system

Question 33

Ion channels overview

Answer 33

1. Receptors that act as a “gate for ions”
2. When a ligand bonds to the receptor the “gate” opens or closes allowing the diffusion of specific ions
3. This initiates a series of events that lead to a cellular response