cell communication and cellular receptors

Question 1

what is cell communication?

Answer 1

• its the process by which cells detect, interpret and respond to signals in their environment
• this allows cells to respond to environmental changes and allows cell-to-cell communication

Question 2

what are the 3 stages of cell communication?

Answer 2

1. receptor activation
2. signal transduction
3. cellular response

Question 3

how are cellular receptors are activated?

Answer 3

• the signalling molecule(ligand) binds to the receptor with high specificity
• binding and release between receptor and ligand is relatively rapid
• ligand binding brings about a conformational change in the receptor with transmits the signal across the cell membrane
• when the ligand is released, the receptor reverts to its inactive state

Question 4

what are the 3 things that cell surface receptors are typically?

Answer 4

1. enzyme-linked receptors
2. G-protein coupled reactions (GPCR)
3. ligand-gated ion channels

Question 5

how do enzyme linked-receptors work?

Answer 5

• the extracellular section of the receptor binds to the signal, activating enzyme activity in the intracellular section
• most are protein kinases

Question 6

how do G-protein coupled receptors work?

Answer 6

• they contain 7 transmembrane domains
• activated receptors bind to intracellular heterotrimeric G proteins( consists of 3 subunits-α,β and Υ)
• Gα then releases bound GDP and binds to GTP
• GTP binding causes disassociation of the heterotrimeric complex
• α subunit and β/Υ dimer interact with other cellular proteins in signal transduction pathways

Question 7

how do ligand-gated ion channels work as cell signal receptors?

Answer 7

the ligand binds causing the ion channel to open and ions flow through the membrane
-these are important for transmission of signals between neurons and muscles or between two neurons

Question 8

what activates intracellular receptors?

Answer 8

• some signalling molecules are hydrophobic so they can travel through the membrane
• these can activate intracellular receptors
• steroid hormones bind to receptors that localise to the nucleus and function as transcription factors

Question 9

what effect do intracellular receptors, such as the ones for steroid hormones do in the cell?

Answer 9

they act as transcription factors which change cell structure, or function in a way that results in a cellular response

Question 10

what are the advantages of second messengers are signal amplification and speed?

Answer 10

signal amplification- binding of the signal to one receptor can cause the synthesis of many cAMP molecules that activate PKA which can phosphorylate many proteins

speed- large amounts of cAMP can be produced very rapidly following ligand binding to receptor, and can diffuse very rapidly through the cell