Question

There are a variety of ways that cells can signal to each other; 2 require direct contact while 3 use receptor-ligand interactions. Briefly describe each; the kind (s) of cell (s) or circumstances where you would find each type of communication. What is the ultimate goal of intracellular signal transduction? Why do cells do this? Why expend so much energy and material? What role does phosphorus play? Briefly explain the difference between necrosis and apoptosis? Why is the latter part of the cell's program?

Answer 1

Question 1

Cell signalling classifications

1. Receptor ligand interaction

a. Paracrine signal - cell communicate to short distance target by the release of chemical messengers. Eg Release of neurotransmitters by neuron terminal while conducting action potential.

b. Autocrine signal - cell produces a ligand which binds to its own receptor. It's also called as self signaling. E.g. Metastasis of cancer cells

c. Endocrine signal - cells secrete chemical substances which travel long distance to reach its target. E.g. Synthesis and transportation of hormones by glands like pituitary, thyroid etc.

2. Direct contact signal

a. Gap junction - it is a tiny water filled channel that connects 2 cells. Small molecules like calcium will pass through these channels. E.g. Plasmodesmata in plants

b. Cell to cell contact - cell with complementary protein bind with each other. E.g. Natural killer cells bind with healthy cells during immune response.