Cell Communication

Question 1

what are the three stages of cell signalling

Answer 1

• receptor activation
• signal transduction
• cellular response

Question 2

what is receptor activation

Answer 2

the binding of a ligant causes a conformational change in a receptor that activates its function

Question 3

what is signal transduction

Answer 3

the activated receptor stimulates a series of proteins that forms a signal transduction pathway

Question 4

what is a cellular response

Answer 4

the signal transduction pathway affects the function and/or amounts of cellular proteins

Question 5

what are enzyme-linked receptors and what is their process

Answer 5

• relay proteins

- protein kinase cascade - transcription factors activated - genes expressed and protein synthesis

Question 6

what are receptor tyrosine kinases and what do they do

Answer 6

enzyme-linked receptors

- recognize various ligands and move phosphates around

Question 7

what is the g-protein coupled receptor series of events

Answer 7

activation of g-protein, production of cAMP, activation of PKA, and activation of proteins

Question 8

what are g-proteins? why are they needed

Answer 8

• links the 1st and 2nd messengers together and is activated when a ligand binds to a receptor at the membrane surface

Question 9

what are the 1st and 2nd messengers

Answer 9

1st: when a ligand binds a cell surface receptor in plasma membrane
2nd: cyclic AMP; acts in the cytoplasm

Question 10

what is amplification

Answer 10

when a small number of signal molecules (ligands) bind to membrane receptors (secondary receptors)

Question 11

what is serotonin an example of? what is the general series of events

Answer 11

• speeds up the speed of communication (causes amplification)
• signal molecules bind to a g-protein coupled receptor which causes activation of the g-protein
• GTP and the activated g-protein attach to an andenylyl cyclase and promotes the synthesis of cAMP from ATP
• cAMP activates PKA by binding to the subunits; this releases active catalytic subunits of PKA
• PKA uses ATP to phosphorylates proteins which causes a cellular response

Question 12

what is epidermal growth factor an example of and what is the series of events?

Answer 12

• enzyme-linked receptor; stimulates cell growth or division
• 2 EGF molecules bind to the receptor subunits and causes them to phosphorylate (change confirmation)
• the phosphorylated receptors are recognized by the first relay protein which changes confirmation so it can interact with the other relay proteins
• the protein kinase cascade happens (the last relay protein activates a protein cascade where sequential protein kinases are activated
• this is ended with the phosphorylation of an Erk protein
• Erk enters the nucleus and phosphorylates Myc and Fos
• the cell responds to these transcription factors and responds accordingly

Question 13

what does the phosphorylation of proteins cause?

Answer 13

produces a cellular response; it will either activate or inhibit proteins

Question 14

what are the 5 types of cell-to-cell communication

Answer 14

• direct intercellular
• contact-dependent
• autocrine
• paracrine
• endocrine

Question 15

what is direct intercellular communication

Answer 15

• signals pass through gap junctions from the cytosol

Question 16

what is contact-dependent cell communication, example

Answer 16

• membrane-bound signals bind to receptors on adjacent cells

- MHCII and TCR

Question 17

what is autocrine communication, example

Answer 17

• cells release signals that affect themselves and nearby target cells
• t cells activating an inflammatory response with IL-2

Question 18

what is paracrine communication

Answer 18

• cells release signals that affect nearby target cells

Question 19

what is endocrine communication

Answer 19

• cells release signals (hormones) that travel long distances to affect target cells

Question 20

what is an enzyme

Answer 20

alter metabolism or other cell functions

Question 21

what are structural proteins

Answer 21

alter cell shape or movement

Question 22

what are transcription factors

Answer 22

alter gene expression, which changes the types and amounts of proteins in the cell