Cell Communication (4)

Question 1

What are the two main ways cells can communicate?

Answer 1

Direct Contact and Chemical Signaling

Direct Contact includes gap junctions in animals and plasmodesmata in plants and cell to cell recognition in both
Chemical Signaling includes paracrine and endocrine signaling

Question 2

What are the types of Direct Contact and how do they work

Answer 2

Gap Junctions (animal cells) and Plasmodesmata (plant cells) exchange ions, small molecules, and second messengers
Cell to Cell Recognition (all cells) require touching cell membrane

Question 3

What are the types of chemical signaling and how do they work?

Answer 3

Short distance –> Paracrine - uses local regulators
Long distance –> endocrine - hormones travel through the circulatory system in animals and vascular tissue in plants

Question 4

What is the first step in cell signaling?

Answer 4

Reception

This involves ligands binding to receptors on target cell membranes.

Question 5

What happens to a receptor when a ligand binds?

Answer 5

The receptor changes shape to start signal transduction

This is similar to the enzyme/substrate connection.

Question 6

What are G-protein coupled receptors?

Answer 6

• Cell-surface transmembrane receptor that works with the help of a G-protein
• G proteins bind GTP

Question 7

What are ligand gated channels?

Answer 7

• gate the opens or closes when receptor changes shape
• lets ions through when opened

Question 8

What are receptor tyrosine kinases? (RTK)

Answer 8

• membrane receptors that catalyze the transfer of phosphate groups from ATP to other proteins
• can trigger multiple signal transduction pathways at once

Question 9

What is the second step in cell signaling?

Answer 9

Transduction

This is a multistep pathway leading to a cell response.

Question 10

What is a phosphorylation cascade?

Answer 10

Protein kinases transfer phosphates from ATP to proteins, while protein phosphatases remove the phosphate creating an on/off effect for proteins in the pathway

Question 11

What are second messengers?

Answer 11

• Ions or small molecules that relay/amplify signals
• these can diffuse quickly throughout the cell unlike large proteins

An example of a second messenger is cyclic AMP (cAMP).

Question 12

What is signal amplification?

Answer 12

The increase in the number of activated products from one step to the next

This process leads to a greater response in subsequent steps.

Question 13

What is the third step in cell signaling?

Answer 13

Response

This can involve changes in gene expression or cell function.

Question 14

What can the response in cell signaling lead to?

Answer 14

Changes in gene expression, cell growth, secretion, or apoptosis

Transcription factors may turn on or off the production of specific proteins.

Question 15

Fill in the blank: Ligands are ________ that bind to receptors.

Answer 15

signaling molecules

Ligands initiate the signal transduction process.

Question 16

True or False: Intracellular receptors are located outside the cell membrane.

Answer 16

False

Intracellular receptors are located inside the cell and interact with ligands that can pass through the membrane.