Module 3: Lesson 3

Question 1

What types of cell signals are there?

Answer 1

Endocrine, paracrine (including autocrine), neuronal, and contact-dependent.

Question 2

What types of signals are slow, and what types are fast?

Answer 2

Slow: cell differentiation, increased cell growth and division
Fast: Cell movement, secretion, and metabolism.
This is determined by the need for changes in gene expression and new protein synthesis.

Question 3

What are transmembrane proteins?

Answer 3

Receptor proteins that bind signal molecules. Example: Notch receptor.

Question 4

What is a form of positive feedback and what does it generate?

Answer 4

A form of positive feedback is to increase the activity of a protein that activated another protein. Positive feedback loops can ignite an explosive response, such as to trigger cell division.

Question 5

What does negative feedback generate?

Answer 5

When a protein is inhibited in negative feedback, the loops can generate oscillations.

Question 6

What are the three major types of cell-surface receptors?

Answer 6

Ion channel-coupled receptors, G protein-coupled receptors, and enzyme-coupled receptors.

Question 7

What are ion channel receptors?

Answer 7

Channel receptors that open when they bind a ligand. They are involved in intracellular signaling, such as Ca2+ in ER.

Question 8

What are G protein-coupled receptors (GPCRs)?

Answer 8

Multi-pass transmembrane proteins that undergoes a conformational change that allows it to bind and activate a G protein after binding to a ligand. It has subunits a, B, and y and uses GTP hydrolysis.

Question 9

What does an active GCPR do?

Answer 9

It activates the G proteins by encouraging the a subunit to release its GDP and pick up GTP.