Block 3 - Lecture 3 Notes

Question 1

Signal transduction

Answer 1

Cellular signaling

Question 2

Cellular signaling is mainly initiated by…

Answer 2

secretion of chemical messengers such as hormones, growth factors, and neurotransmitters

Question 3

Cellular signaling is additionally initiated by…

Answer 3

External signals such as odorants or tastants and metabolites

Question 4

Types of cellular receptors

Answer 4

1. Ligand-gated ion channels
2. GPCRs
3. Catalytic receptors
4. Nuclear receptors

Question 5

Ligand gated ion channels

Answer 5

Integral membrane proteins interact with ion channels and modify flux across channel.
Ion acts as the initial second messenger.

Question 6

Nicotinic ACh receptors

Answer 6

Ligand-gated ion channels
Critical for muscle response to signals from the nervous system to contract.

Question 7

ATP-sensitive K+ channels

Answer 7

Ligand-gated ion channels
Critical for insulin secretion from beta cells of the endocrine pancreas

Question 8

G Protein-Coupled Receptors

Answer 8

• Large class of integral membrane proteins.
• Activate a heterotrimeric complex G Protein.
• Subsequent modulation of an enzyme or ion channel.
• Product of enzymatic activity (ion) is initial second messenger.

Question 9

Examples of GPCRs

Answer 9

B-adrenergic receptors
Alpha 1 and alpha 2 adrenergic receptors
Glucagon receptor

Question 10

Catalytic Receptors

Answer 10

• Activation of enzymatic activity of the receptor itself OR
• Initiation of series of events that (through protein-protein interactions) activate an enzymatic complex.

Question 11

Insulin receptor is which type of cellular receptor

Answer 11

Catalytic

Question 12

Nuclear Receptors

Answer 12

• Located either in the cytoplasm or the nucleus
• Acts as transcription factors to modulate the transcription of specific genes.
• No second messengers are utilized.

Question 13

Initiation of Signaling Event by Plasma Membrane Receptors

Answer 13

1. Recognition
2. Transduction
3. Transmission
4. Modulation of effector
5. Response
6. Termination

Question 14

Recognition

Answer 14

Ligand binds to exofacial aspect of receptor

Question 15

Transduction

Answer 15

Ligand binding induces conformational change in receptor, producing a second messenger

Question 16

Transmission

Answer 16

Second messenger interacts with various intracellular effectors

Question 17

Modulation of the effector

Answer 17

Interaction activates a protein kinase or phosphatase; changes in phosphorylation state of a downstream target alter functionality.

Question 18

Response

Answer 18

Signaling events modify cellular function in highly specific ways

Question 19

Termination

Answer 19

Feedback mechanisms stop signaling events and return cellular function to a basal state

Question 20

Amplification

Answer 20

Increased production of second messengers at each step of multi-signaling cascade –> enhanced activation of a cellular process by several orders of magnitude