Cell Biology

Question 1

Four types of extracellular signaling

Answer 1

Endocrine- hormones from glands traveling to distant site of action
Paracrine- signaling molecule of cell acts on nearby cells
Autocrine- cell responds to signaling molecule it releases itself
4th is signaling between membrane-bound proteins interacting with receptors on adjacent cells

Question 2

Function of intercellular communication

Answer 2

Coordinates metabolism, growth, differentiation and repair

Question 3

Production of inositol triphosphate and diacylglycerol

Answer 3

Produced via hydrolysis of inositol phospholipids , phosphotidyl bisphosphate (PIP2) most NB.
Signaling molecule molecule binds receptor in the plasma membrane causing activation, which activates guanine-nucleotide-binding protein (G protein, known as Gq), which activates inositide-specific phospholipase C (phospholipase C-Beta) which cleaves phosphatidyl bisphosphate into inositol triphsophate (IP3) and diacylglycerol

Question 4

2 roles of IP3

Answer 4

1. Diffuses into cytosol. Binds and opens IP3 gated Ca release channels in ER or to ryanodine receptors in sarcoplasmic reticulum (muscle). To end calcium response, the calcium is pumped out cytosol and IP3 broken down by phosphatases within cell
2. Some IP3 is phosphorylated into IP4 (inositol tetrakisphosphate) which promotes refilling of intracellular calcium stores and or mediates slower or longer-lived responses within the cell.

Question 5

2 fates of diacylglycerol

Answer 5

1. Is cleaned into arachidonic acid, which is a precursor for eicosanoid synthesis
2. Acts as a second messenger. The initial increase in Ca due to IP3 causes protein kinase C to move from cytosol to plasma membrane (where diacylglycerol remains) which is then activated by diacylglycerol

Question 6

How is sustained activation of protein kinase C managed?

Answer 6

Initial wave of diacylglycerol is rapidly metabolized. Therefore a second wave is required for sustained pkC activation and a longer term response . Second wave is released by the phospholipase-mediated cleavage of phosphatidylcholine (the major phospholipid in the cell)

Question 7

2 functions of protein kinase C

Answer 7

Protein kinase c is a serine/threonine protein kinase which regulates the function of other proteins by phosphorylating their serine of threonine residues.
It also alters specific gene transcription

Question 8

2 pathways through which protein kinase C alters gene transcription

Answer 8

1. Catalyses the phosphorylation of mitogen-activated protein (MAP) which phosphorylates and activates transcription factor Elk-1. Elk-1 in conjunction with another protein, serum response factor, binds serum response element, which is a short DNA sequence in the promoter region of the target gene, altering transcription
2. Causes release of kappa-B which moves into the nucleus and activates transcription of specific genes