Chpt 9 Cell Communication

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CHAPTER 9: CELL COMMUNICATION

Why do multicellular organisms need to communicate?

To interact to organize tissues & organs, to perform specific functions of that tissue/organ, and to coordinate their activities so that the organism can develop from a fertilized egg to an adult that can survive and reproduce.

Give 2 ways in which a cell surface receptor differs from an intracellular receptor.

-Is embedded in the cell surface -Binds to hydrophilic ligands

How does an intracellular receptor bring about a cellular response?

1- Hormones cross the plasma membrane & bind to receptors 2- Hormone binding causes receptor conformation to change so it no longer binds to inhibitor 3- Hormone-receptor complex translocates to nucleus 4- Hormone receptor complex binds to DNA, usually turns on transcription but can also turn it off 5-cellular response is a change in gene expression

Describe the various types of signalling

There are four types of signalling: Direct contact, Paracrine Signalling, Endocrine Signalling, and Synaptic Signalling. Direct contact is when two proteins interlock with each other. Direct contact in animals are called gap junctions and in plants are called plasmodesmata. Paracrine Signalling is local signalling that is short lived and only affects cells in the area. Endocrine signalling is long lived and can travel long distances, usually through the blood stream. Synaptic Signalling is between nerve cells and are very close; it is from one nerve cell to another nerve cell.

How does paracrine signalling differ from endocrine signalling?

Paracrine Signalling is local signalling that is short lived and only affects cells in the area. Endocrine signalling is long lived and can travel long distances, usually through the blood stream.

How is paracrine signalling similar to synaptic signalling?

Paracrine Signalling is local signalling that is short lived and only affects cells in the area. Synaptic Signalling is between nerve cells and are very close; it is from one nerve cell to another nerve cell.

Describe the structure of a GPCR

GPCR has 7 transmembrane domains. It has an amino and carboxyl terminal end. It has a ligand binding site and a G-protein binding site.

Name 2 effector proteins of GPCRs and their second messengers.

Two effector proteins of GPCR are Adenylyl cyclase and Phospholipase C. Their second messengers are cAMP and Ca2+, respectively.

What is the function of a second messenger? What characteristics must a molecule have to be called a second messenger?

The function of a second messenger is to help relay the signal. Second messengers must be small and water soluble molecules/ions.

What determines specificity of cell signalling?

Different cells have different collections of proteins which determine specifity of cell signalling.

What is a protein kinase? How does it differ from a phosphatase?

Protien Kinase is an enzyme that changes the cell by adding phosphate or phosphorelating it. On the other hand, phosphotase modifies the cell by removing phosphates.

The cell surface receptors play an important role in cell identity. Explain

Describe 2 ways in which cells adhere.

Cells adhere through tight junctions and through anchoring junctions. Tight junctions create sheets of cells; the plasma membrane fuses. Anchoring junctions connect the cytoskeleton of adjacent cells; it occurs in high stress areas such as the skin and muscles.

Describe the communication junctions in animals and plants

They permit small molecules and ions to pass between cells. In animals gap junctions are used, which are made up of connexon. In plants plasmodesmata are used, which are formed through breaks in the cell wall and fusing of the plasma membrane.

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