Unit 7

Question 1

Signal transduction is the process of converting an extracellular (_______ A) into an intracellular signal (______ B) in a _______.

Answer 1

Signaling molecule A,
Signaling molecule B,
Target cell

Question 2

Cells communicate by means of:

Answer 2

extracellular signaling molecules

Question 3

Intracellular signal can initiate series of intracellular rxn’s that regulate: (6 examples)

Answer 3

Transcription,
Survival,
Protein synthesis,
Movement,
Cell death,
Metabolic changes

Question 4

Six steps in signaling

Answer 4

1. Signaling molecule synthesis by signaling cell
2. Signaling molecule released by signaling cell
3. Signaling molecule transport to target cell
4. Signal detection by specific receptor protein
5. Change in cellular metabolism, function, or development triggered by the receptor-signaling molecule complex
6. Removal of signaling molecule; Terminating cellular response

Question 5

Signaling can be classified into 4 types that act over short or long distances:

Answer 5

1. Autocrine signaling
2. Paracrine signaling
3. Endocrine signaling
4. Contact-dependent signaling

Question 6

Autocrine signaling definition

Answer 6

Cells respond to SM’s that they release themselves.

Question 7

Autocrine signaling is common in:

Answer 7

cancer cells, which overproduce and release growth factors that stimulate inappropriate, unregulated growth and division of themselves, leading to cancer development

Question 8

Paracrine signaling definition

Answer 8

SM’s released by signaling cell into the extracellular medium act locally to affect target cells in close proximity to the signaling cell

Question 9

Endocrine signaling definition

Answer 9

SM’s (hormones), act on target cells distant from their site of synthesis by endocrine cells.

Hormones made in endocrine cells secreted into blood stream & can be distributed widely throughout body.

Question 10

Contact-dependent signaling definition

Answer 10

A membrane-anchored signal in plasma membrane of the signaling cell binds to a receptor molecule embedded in the plasma membrane of the target cell.

Question 11

What does contact-dependent signaling require?

Answer 11

Requires cells to be in direct membrane-to-membrane contact with each other and does not require the release of a signaling molecule.

Question 12

Which of the four signaling mechanisms can be glycosylated?

Answer 12

Contact-dependent signaling

Question 13

The extracellular signaling molecule alone is not the signal. The signal depends on:

Answer 13

How the target cell interprets the signaling molecule, which is dictated by intracellular signaling pathways.

Question 14

Signaling pathways consist of a series of:

Answer 14

Proteins (&/or) 2nd messengers

Question 15

Each protein in a pathway alters the ____ or ______ of the next protein. In some cases, the intracellular signaling molecule can be a small molecule (e.g. cAMP, Ca2+). These are referred to as ______.

Answer 15

Conformation,
Activity,
2nd Messengers

Question 16

Protein conformation in intracellular signaling is usually altered by _______.

Answer 16

Phosphorylation: If something (generally) gets phosphorylated in a protein activation pathway, that protein becomes active

Question 17

____ add phosphate groups, while ______ remove them. Very often signaling proteins rely on _______.

Answer 17

Kinases,
Phosphorylases,
Protein kinases

Question 18

When signaling is mediated by proteins, upon activation of the signaling cascade there are four types of molecular switches: (To turn on/off signaling pathway)

Answer 18

1. Phosphorylation / dephosphorylation
2. GTP-binding
3. Assembly-Disassembly of protein complexes
4. Proteolysis

Question 19

Which is the only irreversible of the four molecular switches during cellular signaling mediation:

Answer 19

Proteolysis

Question 20

Four ways protein phosphorylation can change protein behaviour:

Answer 20

1. Activate/inactivate an enzyme.
2. Promote/interfere with protein-protein interactions.
3. Change the subcellular location of the protein.
4. Trigger protein degradation.

Question 21

Kinase _____’s a signal, and phosphatase _____’s a signal

Answer 21

Activate,
Inactivate

Question 22

GTP binding as a molecular switch example

Answer 22

GPCR

Question 23

In the absence of a signal, the GTP-binding protein is bound to ___. Signals activate the release of it and the subsequent binding to ___.

Answer 23

GDP,
GTP

Question 24

A GTP-binding protein is ___ when bound to GTP and _____ when bound to GDP.

Answer 24

Active,
Inactive

Question 25

Difference between the Rab vs. GTP binding proteins

Answer 25

Rab family are single polypeptides

GTP-binding proteins are heterotrimeric

Question 26

in GTP binding, the ____ activity of these intracellular signaling proteins hydrolyses the bound ____ to GDP and Pi, thus converting the _____ form back to the _____ form.

Answer 26

GTPase,
GTP,
Active,
Inactive

Question 27

Many signal-transduction cascades contain multiprotein signaling complexes that _____ and ______ protein complexes

Answer 27

Assemble,
Dissassemble