Signal Transduction

Question 1

Signal Transduction also known as

Answer 1

Cell signalling.

Question 2

Cell to cell communication is essential for what?

Answer 2

Both multicellular and unicellular organisms.

Question 3

Cells most often communicate with each other using what?

Answer 3

Chemical Signals

Question 4

Example of Chemical Signals in use

Answer 4

Fight or Flight response triggered by epinephrine.

Question 5

What did Earl W. Sutherland do?

Answer 5

He discovered that epinephrine causes the breakdown of glycogen, and so he suggested that cells receiving signals undergo three processes: reception, transduction, and response.

Question 6

Reception

Answer 6

A signalling molecule (ligand) binds to a receptor protein, causing it to undergo a conformational change.

Question 7

ligand

Answer 7

any chemical that binds to a receptor

Question 8

The binding between a signalling molecule (ligand) and a receptor protein can be described as what?

Answer 8

Very specific and reversible.

Question 9

Most signal receptors are

Answer 9

Plasma membrane proteins.

Question 10

Most water-soluble signalling molecules do what?

Answer 10

Bind to specific sites on receptor proteins that span the plasma membrane.

Question 11

How many types of membrane receptor proteins are there? What are they?

Answer 11

Three - G protein-coupled receptors, Receptor Tyrosine Kinases, and Ion Channel receptors (from information processing)

Question 12

G protein coupled receptors name meaning

Answer 12

Called “G” because they require GTP

Question 13

GTP

Answer 13

Guanosine Triphosphate

Question 14

Receptor Tyrosine Kinase Function

Answer 14

Adds phosphate (hence Kinase) to amino acid tyrosine.

Question 15

Largest family of cell-surface receptors

Answer 15

G protein-coupled receptors. (GPCRs)

Question 16

Does the GPCR function alone? If not, with what does it function?

Answer 16

The GPCR is a plasma membrane receptor that functions with the help of a G protein.

Question 17

G Protein function

Answer 17

The G protein acts as an on/off switch: when GDP (guanosine diphosphate) binds to the G protein, the G protein is inactive.

Question 18

Steps of G-protein receptor function

Answer 18

Water-soluble signalling ligand binds to a G-protein receptor, resulting in a conformational change of the receptor. This conformational change allows the cytoplasmic side of the receptor to bind to an inactive G-protein, replacing its GDP with GTP, thereby activating it. The active G-protein binds to an enzyme in a transduction pathway, which causes it to once again become inactive.

Question 19

Why are receptor tyrosine kinases (RTKs) so difficult to study?

Answer 19

A RTK can trigger multiple signal transduction pathways.

Question 20

Abnormal functioning of RTKs is associated with what?

Answer 20

Cancer

Question 21

Receptor Tyrosine Kinases Functioning Steps

Answer 21

Signalling molecule binds to receptor tyrosine kinase, which leads to dimerization. Dimerization causes the receptor to become phosphorylated and therefore active. The activated receptor binds to proteins in a transduction pathway.

Question 22

Signalling molecules for Receptor Tyrosine Kinases (RTKs)

Answer 22

Growth Hormone.

Question 23

Where are intracellular receptor proteins found?

Answer 23

Intracellular receptor proteins are found in the nucleus, or cytosol of target cells.

Question 24

Intracellular

Answer 24

Inside of the cell

Question 25

What kind of chemical messengers can bind to intracellular receptor proteins?

Answer 25

Small or hydrophobic chemical messengers.

Question 26

Examples of chemical messengers that can readily pass through the membrane and bind to receptors

Answer 26

Steroids (hydrophobic) and thyroid hormones (small)

Question 27

What does a chemical messenger, when binded to a intracellular receptor, form? What does this result do?

Answer 27

Chemical messengers bind to intracellular receptors to form an activated hormone-receptor complex. This can act as a transcription factor.

Question 28

Transduction

Answer 28

Cascades of molecular interactions

Question 29

Function of Cascades

Answer 29

Cascades relay signals from receptors to target molecules in the cell.

Question 30

Cascades usually involve...

Answer 30

Many steps

Question 31

Benefits of cascades

Answer 31

1. Multiple steps allow for more opportunities of coordination and regulation of cellular response. 2. Allows for amplification of signal.

Question 32

The molecules that relay a signal from a receptor to a response are:

Answer 32

mainly proteins.

Question 33

Cascade described with a colloquial term

Answer 33

Domino Effect.

Question 34

2 pathways of transduction

Answer 34

1. Protein phosphorylation and dephosphorylation | 2. Second Messengers.

Question 35

How is a signal transmitted?

Answer 35

A signal is transmitted by a series of protein phosphorylations.

Question 36

Protein Kinases (function)

Answer 36

In phosphorylation and dephorylation system/cascade, the protein kinases transfer phosphates from ATP to serine or threonine.

Question 37

What causes dephosphorylation?

Answer 37

Protein Phosphatases (PP) remove phosphates from proteins, a process called dephosphorylation.

Question 38

The final protein in the cascade does what when activated?

Answer 38

Triggers a cellular response.

Question 39

The phosphorylation and dephosphorylation system in the end does what?

Answer 39

It turns cellular activities on and off, or up or down (increasing or decreasing activity), as required.

Question 40

Which protein kinases are activated? which are inactive?

Answer 40

Phosphorylated proteins are active, unphosphorylated proteins are inactive.

Question 41

Second Messengers

Answer 41

Second Messengers are small, non-protein, water soluble molecules or ions.

Question 42

How do second messengers spread throughout the cell?

Answer 42

By diffusion

Question 43

Second messengers participate in which pathways?

Answer 43

Pathways initiated by GPCRs and RTKs.

Question 44

Most common second messengers

Answer 44

Cyclic AMP, and (Calcium ions and inositol triphosphate (IP3))

Question 45

two plasma membrane enzymes involved in cyclic AMP (cAMP)

Answer 45

Adenyl Cyclase and Phosphodiesterase

Question 46

Adenyl Cyclase Function

Answer 46

Converts ATP to cAMP in response to an extracellular signal. Plasma membrane enzyme

Question 47

Phosphodiesterase Function

Answer 47

Plasma membrane enzyme that converts cAMP to AMP to terminate the signal.

Question 48

What triggers cAMP formation?

Answer 48

G proteins, G protein-coupled receptors, and protein kinases.

Question 49

What does cAMP do?

Answer 49

cAMP usually activates protein kinase A

Question 50

Some G protein systems can actually do what?

Answer 50

Some G protein systems can inhibit Adenyl Cyclase.

Question 51

Why does calcium act as an important secondary messenger in many pathways?

Answer 51

Cells can easily regulate its concentration.

Question 52

How do cells regulate the concentration of Calcium?

Answer 52

Using Ca2+ - ATPases, which pump calcium against the concentration gradient using ATP and gated calcium channels.

Question 53

Signalling Molecule (ligand) alternative term

Answer 53

First messenger

Question 54

Ca 2+, is it more concentrated inside or outside of the cell?

Answer 54

More concentrated outside of the cell

Question 55

What helps regulate Ca2+ concentration?

Answer 55

inositol triphosphate (IP3)

Question 56

How does inositol triphosphate regulate Ca2+ concentration in the cell? (Steps)

Answer 56

Phospholipase is activated by active G-protein. Active phosopholipase cleaves phosphotidylinositol into inositol triphosphate (IP3) and diacylglycerol. Inositol triphophate binds to Calcium gated channels in the endoplasmic reticulum (ER), opening them and causing an influx of Calcium ions into the cell, which activate the next protein in the cascade.

Question 57

What does inositol triphosphate and diacylglycerol have in common?

Answer 57

They are both second messengers.

Question 58

Cellular response takes place where?

Answer 58

in the cytoplasm or nucleus

Question 59

Function of Cell signalling pathways

Answer 59

Cell signalling leads to regulation of transcription and cytoplasmic activities. Many signalling pathways regulate the synthesis of enzymes and other proteins, usually by turning genes on or off in the nucleus. The last activated molecule in a signalling pathway may function as a transcription factor. Some signalling pathways regulate the function of enzymes rather than their synthesis.

Question 60

Example of a signalling pathway that regulates the function of an enzyme rather than its synthesis

Answer 60

Epinephrine

Question 61

Relay molecules

Answer 61

Molecules that transmit the signal from the receptor to the cellular response.

Question 62

Termination of the Signal Process

Answer 62

Decrease in ligand concentration causes more receptors to be unbound. Unbound receptors revert to an inactive state. Relay molecules return to an inactive state with the help of enzymes such as GTPases, phosphodiesterases, and protein phosphatases(PP)

Question 63

GTPases

Answer 63

Hydrolyzes GTP attached to G-proteins

Question 64

Phosphodiesterases

Answer 64

converts cAMP to AMP to terminate the signal

Question 65

Protein Phosphatases (PP)

Answer 65

Deactivates active phosphorylated proteins by removing phosphates.