Cell Communication

Question 1

Synaptic signaling

Answer 1

Neurotransmitters cross the synapse to send a message

Question 2

Paracrine signaling

Answer 2

Local communication. Cells secrete substance that is either absorbed by nearby cells or is broken down by the extra cellular fluid

Question 3

Endocrine signaling

Answer 3

Provides a mechanism for distributing signals throughputs a multicellular organism. Example: hormones

Question 4

Signal transduction pathway

Answer 4

Signal (first messenger) > receptor > proteins/ second messengers > cellular responses

Question 5

First messengers

Answer 5

Ligands. Either hydrophilic (can’t cross the phospholipid bilayer, bind to membrane receptors) or
Hydrophobic (bind to intercellular receptors)

Question 6

Membrane receptors

Answer 6

Transmembrane proteins. From outside the cell to within the membrane

Question 7

Intracellular receptors

Answer 7

Proteins inside the cytoplasm or nucleus

Question 8

Second messengers

Answer 8

Small, non protein molecules

Hydrophilic, hydrophobic, or gaseous

Question 9

Relay/ response proteins

Answer 9

Proteins that participate in moving the signal to target areas (along with second messengers)

Question 10

Signaling cascade

Answer 10

A series of enzymatic reactions. Amplifies the signal more the longer it is

Question 11

Kinase cascade

Answer 11

A signal cascade consisting of different kinase enzymes. Kinases phosphorylase their substrates, so te end result is the phosphorylation of the target protein.

Question 12

Scaffold proteins

Answer 12

Improve efficiency of signaling cascade by holding all participating enzymes in close proximity

Question 13

Protein phosphatase

Answer 13

An enzyme that dephosphorylatws its substrate. When it dephosphorilates kinases in a cascade, it serves to terminate the signal

Question 14

Direct contact communication junctions

Answer 14

Gap junctions: animals. Allow small molecules and ions to pass between cells
Plasmodesmata: plants. Tunnels of cytoplasm between cells

Question 15

Gated ion receptors

Answer 15

A transmembrane protein that contains a gated channel. A ligand-gated ion receptor responds to a specific ligand, while a voltage-gated ion receptor responds to voltage differences. Example: acetylcholine binds to ligand gated receptors, the receptor opens, allowing sodium ions to enter the cell. This initiates a neural impulse as voltage gated ion channels throughout the nerve cell open.

Question 16

G Protein-Coupled Receptors (GPCRs)

Answer 16

G protein receptors activate a G protein, which goes on to activate something else. G proteins are called such because they have GDP (when turned off, GTP when on) out groups.

Question 17

Intracellular Receptors

Answer 17

Receptors that function from inside the cell. Signaling molecules bind to the receptors, creating a receptor-molecule complex, which acts as a transcription factor (inhibiting or promoting genes). Deactivation occurs when the complex is enzymatically degraded. Examples: estrogen or testosterone

Question 18

Give examples of problems that occur when signaling pathways don’t function properly

Answer 18

Cholera bacteria secrete a toxin that disrupts the function of GPCRs in intestines by making it impossible to disable them. In these cells, the protein regulates chlorine. When locked in its active state, it generates cAMP constantly, causing chlorine to be transported out of the cell. Water follows the chlorine through osmosis, leading to diarrhea and death.