Cell Signaling

Question 1

What are the three main stages of cell signaling

Answer 1

Reception
Transduction
Response

Question 2

Reception

Answer 2

A signaling molecule binds to a protein receptor and make it do things
The receptor can be on the plasma membrane or inside the cell

Question 3

Transduction

Answer 3

A series of relay molecules that carries the signal into the cell and amplifies the signal

Question 4

Response

Answer 4

This goes on inside the cell and activates cellular response

Question 5

Ligand

Answer 5

This is a small molecule that binds. The binding is capable of producing a signal.
**These are signaling molecules

Question 6

The ligand will only bind and activate one specific receptor protein. True/ False

Answer 6

True

Question 7

List the three general class of receptors

Answer 7

G protein-coupled receptors
Receptor tyrosine Kinases
Ion channel receptors

Question 8

Receptors inside the cell(cytoplasmic) do not responds\ to the membrane-permeable(small and hydrphobic) signals of the cell. True/False

Answer 8

False

Question 9

G protein-coupled receptors (GPCR)

Answer 9

It has 7 transmembrane domains
When a signaling molecule binds with a GPCR this cause a conformational change in the GPCR.
This change can trigger a reaction with the GPCR and a G protein

Question 10

G protein

Answer 10

This is a membrane bound enzyme that is part of the signal transduction system
G protein can be bound to the GDP(off site) or GTP (on site)

Question 11

Steps to activate G protein

Answer 11

1. Ligand binds to the GPCR, the receptor changes shape
2. This allows the G protein to dock it
3. GDP is released and GTP is loaded in. This activates the g protein

Question 12

What happens to the activated G protein

Answer 12

1. The activated g protein binds an inactive enzyme and activate it
2. The enzyme can usually make cyclic AMP (cAMP - Cyclic Adenosine Monophosphate)
   3 This can initiate the signal transduction

Question 13

What happens when GTP is hydrolyzed?

Answer 13

When GTP is hydrolyzed, it releases phosphate and turns to GDP

Question 14

Rhodopsin

Answer 14

one of a few GPCR in rod cell(a type of photoreceptors) that make up your eyes

Question 15

Retinal

Answer 15

a small molecule cofactor (non protein or metallic compound that helps the enzyme catalyze reaction) that is bound to the receptor.

Question 16

A retinal absorbs an incoming photon of light. True/False

Answer 16

True. This causes the retinal to go from cis to trans conformation, the GCPR changes shape and start signal transduction

Question 17

When a ligand binds to a receptor tyrosine kinases what happens?

Answer 17

The receptor (single alpha helixes) comes together to form dimer.
**they were separate before.

Question 18

Kinase

Answer 18

An enzyme that can add a phosphate group onto something(other molecules)

Question 19

How is the receptor activated in receptor tyrosine kinases?

Answer 19

It is activated when the two monomers add phosphate to the hydroxyl group on the R groups of the tyrosine

Question 20

Does the phosphorylated tyrosines act as docking sites for relay proteins to bind and become activated. True/False

Answer 20

True. This action kicks off signal transduction pathways

Question 21

Example of use of GPCR

Answer 21

Smell and taste signaling (Ca+ or Na+ channels)
Example of GPCR is epinephrine

Question 22

Examples of use of Receptor Tyrosine Kinases(RTKs)

Answer 22

Some RTKs regulate basic cell division like
- Triggering cell division (stem cells)
- Differentiation of cell into different cell types
- Survival of cell: if it goes into the apopthesis(cell suicide) or not.

Question 23

Function of RTKs

Answer 23

They trigger cell division and ‘guide’ what type of cell the divided cell will differentiate into.

Question 24

Ligand-gated Ion channel receptors

Answer 24

When the ligand come into contact with the Ligand-gated Ion channel receptors, the gate open for the ions. These lets the ions inside (down their concentration gradient), when the ligand leaves the gate closes.

Question 25

The ions don't activate signal transduction. True/ False

Answer 25

False

Question 26

Example of use for Ligand-gated Ion Channel Receptors

Answer 26

This happens a lot in neurotransmission

Question 27

Transcription Factors

Answer 27

These are proteins that binds to DNA at specific nucleotides. Depending on what the body needs they turn ON or OFF the transcription of specific genes

Question 28

Some ligand cross the plasma membrane. True / False

Answer 28

True. An example is steroid

Question 29

Phosphorylation Cascades : process of transduction

Answer 29

A relay molecule activate the protein kinase(enzyme) by adding a phosphate. This goes on until a cellular response is made

Question 30

Protein phosphates remove the phosphates from the cellular response. True/ False

Answer 30

True. All kinases and everything is shut off

Question 31

Secondary Messengers

Answer 31

These are inside the cell. They either trigger other transduction processes, or directly trigger cellular response

Question 32

Examples of Secondary Messengers

Answer 32

Calcium Ions Cyclic AMP

Question 33

Cyclic AMP

Answer 33

They are made by ATP. An enzyme called adenylyl cyclase converts ATP into cAMP

Question 34

Phosphodiesterase

Answer 34

This breaks the ring of cAMP and turn it into adenosine monophosphate (AMP).

Question 35

Advantage of having a multi-step transduction

Answer 35

This allows for greater control of how 'big' the signal output will be. Amplification of signal Different cell types respond/interact to signaling differently rapid signaling from dilute hormones

Question 36

What are the types of signaling

Answer 36

Autocrine Endocrine Synaptic Paracrine Signal through cell-cell contact

Question 37

Endocrine Signaling

Answer 37

This happens in the bloodstream. It occurs over long distance between hormone producing molecules. Often from the brain.

Question 38

Paracrine Signaling

Answer 38

Occurs between cell in close proximity with each other.

Question 39

Synaptic Signaling

Answer 39

Under paracrine signaling. Nerve cells transmit signals. the synapse, the junction between two nerve cells where signal transmission occurs.

Question 40

Autocrine Signaling

Answer 40

A cell signals to itself. it releases a ligand that binds to the receptor on its surface

Question 41

Signal through cell-cell contact

Answer 41

Gap junction are channels that directly connect neighboring cells

Question 42

Crosstalk

Answer 42

The activation of relay molecule(transduction pathway) can influence or inhibit the response of other transduction pathways

Question 43

The different signaling pathways that could happen when a ligand binds to a receptor

Answer 43

The normal pathways: signaling molecule -> receptor -> relay molecules - > Response Signaling Molecule -> Receptor -> different Relay Molecule -> different responses Crosstalk: two different ligand -> two different receptors -> two different relay molecules that affect each other(increase or inhibit) -> response same Ligand -> different receptor - > different relay molecules ->Response