Cellular Communications: Introduction

Question 1

What pathway involves the binding of extracellular signalling molecules and ligands to receptors located on the cell surface or inside the cell that trigger events inside the cell to invoke a response?

Answer 1

Signal transduction pathway

Question 2

List the stages in cellular communication.

Answer 2

1. Synthesis of signaling molecule
2. Release of signaling molecule
3. Transport of signaling molecule to the target
4. Detection of signal by a receptor
5. Response of cell to the signal (transduction)
6. Termination of signaling

Question 3

In what ways do the cell respond to the signal?

Answer 3

1. Direct response e.g. channels, enzyme activation
2. Second messenger system (G-protein coupled receptor)
3. Protein kinases (phosphorylation)
4. Transcription factors (cytosolic receptors)
5. Nuclear factors e.g. thyroid hormones

Question 4

State the types of cell communication (classification of signals).

Answer 4

1. Intracrine signals - produced by the target cell and stay within the target cell
2. Autocrine signals - produced by the target cell, are secreted, and affect the target cell itself via receptors (sometimes, they can target the same type of cell as the emitting cells e.g. immune cells)
3. Juxtracrine signals - target adjacent (contact-dependent signaling) cells (capable of affecting either the emitting cell or cells immediately adjacent)
4. Paracrine signals - target cells in the vicinity of the emitting cell
5. Endocrine signals - target distant cells. they produce hormones that travel through blood to reach all parts of the body
6. Synaptic signaling - long distance through neural system

Question 5

Steroid hormones act through intracellular receptors and thus may be considered to be _____________________.

Answer 5

intracrines

Question 6

Cytokine interleukin-1 in monocytes is an example of an ____________ because when it is produced in response to external stimuli, it can bind to cell-surface receptors on the same cell that produced it.

Answer 6

autocrine

Question 7

_______________ signalling is a type of cell-cell or cell-ECM signaling in multicellular organisms. It plays an important role in development of cardiac and neural function, and in immune response.

Answer 7

Juxtacrine

Question 8

What are the 3 types of juxtacrine signaling?

Answer 8

1. Cell-cell signaling
2. Communicating junctions
3. Cell-ECM signaling

Question 9

The following are true about cell-extracellular matrix signaling except?
A. cells can themselves interact by contact with extracellular matrix molecules and as such, this can be considered an indirect cell/cell communication
B. an extracellular matrix glycoproteinand a membrane protein interact
C. links the intracellular compartments of two adjacent cells, allowing transit of relatively small molecules
D. cells use mainly the receptor integrin to interact with ECM proteins
E. this signaling can influence the cell cycle and cellular differentiation

Answer 9

Choice C.

Question 10

The neural control centre for all endocrine systems is the ________________.

Answer 10

hypothalamus

Question 11

State the features of cellular communication.

Answer 11

1. extracellular signal molecules bind to specific receptors
2. extracellular signal molecules can act over either short or long distances
3. signaling proteins act as molecular switches
4. signaling complexes enhance the speed, efficiency and specificity of the response
5. interactions between intracellular signaling proteins are mediated by modular binding domains
6. a cell can remember the effect of some signals
7. cells can adjust their sensitivity to a signal
8. different cells can respond differently to the same extracellular signal molecule (e.g. the neurotransmitter acetylcholine which stimulates the contraction of skeletal muscle cells, but it decreases the rate and force of contraction in heart muscle cells)

Question 12

Second messengers
A. are substances that interact with first messengers outside cells.
B. are substances that bind to first messengers in the cell membrane.
C. are hormones secreted by cells in response to stimulation by another hormone.
D. mediate the intracellular responses to many different hormones and neurotransmitters.
E. are not formed in the brain.

Answer 12

Choice D.