Cell Signaling

Question 1

*What is the associated effector and 2nd messenger for Gs alpha protein?

Answer 1

Gs protein:
Effector: stimulation of Adenyl cyclase
2nd Messenger : cAMP (increased)

Question 2

*What is the associated effector and 2nd messenger for Gi alpha protein?

Answer 2

Gi protein:
Effector: inhibition of Adenyl cyclase
2nd Messenger: cAMP (decreased)

Question 3

*What is the associated effector and 2nd messenger for G-olf alpha protein?

Answer 3

G-olf alpha protein:
Effector: activates Adenyl cyclase
2nd Messenger: cAMP (increased)

Question 4

*What is the associated effector and 2nd messenger for Gq alpha protein?

Answer 4

Gq protein:
Effector: Phospholipase C
2nd Messenger: IP3, DAG (increased)

Question 5

*What is the associated effector and 2nd messenger for G o alpha protein?

Answer 5

G o protein:
Effector: Phospholipase C
2nd Messenger: IP3, DAG (increased)

Question 6

*What is the associated effector and 2nd messenger for G t alpha protein?

Answer 6

Gt protein:
Effector: cGMP phosphodiesterase
2nd Messenger: cGMP (decreased)

Question 7

Name some of the cell responses that are mediated by cyclic AMP, including the extracellular signal and target tissue

Answer 7

1. Extracellular signal: Adrenaline
   Target tissue: Heart
   Response: increase in heart rate and force of contraction
2. Extracellular signal: Adrenaline
   Target tissue: Skeletal muscle
   Response: glycogen breakdown
3. Extracellular signal: Adrenaline and glucagon
   Target tissue: Fat
   Response: breakdown of fat
4. Adrenocorticotropic Hormone (ACTH)-
   Target tissue: Adrenal gland
   Response: cortisol secretion

Question 8

increase in heart rate, glycogen breakdown, fat breakdown and cortisol secretions are all cell responses mediated by which secondary messenger?

Answer 8

cyclic AMP

Question 9

Which cell responses are mediated by secondary messenger Phospholipase C?

Answer 9

glycogen breakdown, secretion of amylase (digestive enzyme), contraction and aggregation.

Question 10

describe the cell responses mediated by Phospholipase C activation and be sure to include signal molecules, target tissue and major response.

Answer 10

1. signal Molecule: Vasopressin (peptide hormone)
   Target tissue: Liver
   Response: glycogen breakdown
2. signal Molecule: Acetylcholine
   Target tissue: pancreas
   Response: secretion of Amylase (digestive enzyme)
3. signal Molecule: Acetylcholine
   Target tissue: smooth muscle
   Response: contraction
4. signal Molecule: Thrombin (proteolytic enzyme)
   Target tissue: blood platelets
   Response: aggregation

Question 11

Describe the special case for effector K+ channel and include which G proteins regulate the effector and it’s response.

Answer 11

K+ channel is the associated effector.
G alpha, G beta and G gamma proteins all regulate the effector K+ channel
induces response: change in membrane potential

Question 12

what process can be described as “At the core of life” ?

Answer 12

Cell communication- at the core of life.
Many cells communicate and work together for functions of surviving, dividing and differentiating.
Without the existence of cells, no one would be able to live (dead).

Question 13

What happens to cell’s core of life with the development of a disease?

Answer 13

A disease disrupts normal cell signaling (interactions between cells)
Hence if you understand, network and signals, you can correct and control the signals if necessary.

Question 14

What occurs during signal transduction?

Answer 14

1. Signal 2. Reception 3. Cell’s response
   Signal (from environment, or outside cell) reaches cell.
   Cell receives the signal, and will create a cellular response to signal.

Question 15

In signal transduction, what is needed to receive the signal? what is the cell that has the receptors?
What happens if the

Answer 15

Receptor needed to receive signal

Target cell- has receptors.

Question 16

What is signal transduction?

Answer 16

process of transmitting a signal to a cell to generate a cellular response
involves converting one signal into another signal.

Question 17

Describe the example of signal transduction using a phone, and be sure to include target cell, intra/extracellular signal.

Answer 17

When you get a call from a friend, the phone (target cell) will convert radio signal, which travel in the air to a sound wave, which you will hear on the phone when listening to friend talk.
The radio signal IN the phone will be come OUT as Sound signal.

Question 18

What is the difference between the extracellular signals and intracellular signals in cells?

Answer 18

The MEMBRANE between the two signals.

The extracellular signal will come into membrane and be converted out as a intracellular signal.

Question 19

what happens if a ligand does not bind to a receptor? what happens if cell does not have a receptor for particular ligand?

Answer 19

NO CELLULAR RESPONSE, if ligand does not bind to receptor.

if cell has no receptors for a certain ligand (example X), it is NOT a target cell.

Question 20

differentiate between the type of molecules used for cell-surface receptors vs intracellular receptors.

Answer 20

large, Hydrophilic signal molecules bind to cell surface receptors.
small, hydrophobic signals easily bind to intracellular receptors.
signals maybe transmitted from carrier proteins.

Question 21

What happens to the budding yeast in response to mating factor or pheromone released in culture?

Answer 21

in response to pheromone, the yeast cells will become elongated (change shape from round to elongated)
the elongated shape, is due to yeast making more phospholipids (happens fast)

Question 22

Explain the list of events that occur when a cell responds to a signal. provide examples.

Answer 22

When an extracellular signal binds to receptor, it will be converted into intracellular signal
effector proteins (ex: metabolic enzyme, cytoskeletal protein) will then receive intracellular signal and target cell will respond. 
Ex: signal that bind to receptor can alter metabolism, alter cell shape and movement or alter gene expression

Question 23

Differentiate between the signaling response speed in protein function versus protein synthesis.

Answer 23

Signaling responses that occur FAST (secs to mins) can alter protein function, through intracellular signaling however
to alter protein synthesis (like transcription of developmental processes), it will be SLOW (mins to hrs) and take a long time to occur (using cell-surface receptor proteins)

Question 24

What are the 4 types of signaling ? Describe the signaling processes that occur in each case. Which types of signaling are up close, vs at a distance?

Answer 24

Contact-dependent- receptor at cell’s surface that signal can bind to
Paracrine signals will activate target cells nearby
Synaptic -electric signal travel down axon, along terminal then convert to chemical and go to synaptic cleft
Endocrine- signal molecules travel into blood stream to eventually reach target cells.
contact-dependent and paracrine are up close signals;
while synaptic and endocrine (longest distance) are long distance

Question 25

What is a gap junction and how does it affect the cell? How does it affect both cells?

Answer 25

Gap junction- tube that connect 2 different cells. | What ever happens to one cell will happen to the other cell

Question 26

What kind of signaling is autocrine signaling? Provide an example

Answer 26

Autocrine signaling is a form of paracrine signaling, where cells respond to the local mediators or signals that they produce themselves. coordination of groups of identical cells, each cell will receive a strong autocrine signal. autocrine signals generate a lot of signals in short time frame.

Question 27

Describe the concept behind Negative feedback and positive feedback. What's an example of negative feedback?

Answer 27

Negative feedback: if you have enough of product, you can inhibit production of reactant or substrate (regulation) Positive feedback: to produce more of a product, you can add more of the reactant or substrate signal kinase will phosphorylate and activate an enzyme kinase. Then eventually negative feedback will allow phosphatase to remove phosphate from initial enzyme (that was activated) and will inactivate enzyme

Question 28

describe the concept of smooth muscle relaxation and contraction in terms of lumen of blood vessel. What is the purpose of lumen of blood vessel? what happens to lumen when muscle contracts?

Answer 28

The lumen of blood vessel is a cavity through which blood flows. presence of acetylcholine will allow muscles to contract, which makes lumen of blood vessel become smaller. meanwhile, when muscle relaxes, lumen becomes larger.

Question 29

What two compounds lead to relaxation of muscles? what other compounds must be activated for muscle relaxation to occur?

Answer 29

Acetylcholine and Viagra both lead to relaxation of muscles (larger lumen) Acetylcholine binds to receptor, activate phospholipase C which activates IP3, eventually NO, binds to receptor and activate guanylate cyclase (protein kinase G) which leads to relaxation.

Question 30

Differentiate between a reaction with no scaffold protein, vs a reaction with a scaffold protein? what occurs?

Answer 30

a reaction with signal bound to receptor and scaffold will make reaction occur faster, while reaction without scaffold will take a longer time to occur, and require more energy.

Question 31

What are the two main examples of molecular switches? distinguish between GAP and GEF

Answer 31

signaling by protein phosphorylation and GTP binding proteins. protein phosphorylation: - protein kinase will hydrolyze ATP and form ADP which will turn signal on. Phosphorylation also changes shape. -protein phosphatase will form bind gdp and form gtp which will turn signal off. GTP binding proteins: When you bind GTP (lead to GDP) signal will turn on (phosphorylate- conformation change) When you hydrolyze GTP (bind GDP) you will remove phosphate and turn SIGNAL OFF. GAP- GTPASE activating protein- give up GTP faster (GTP hydrolysis) turn off signal GEF- GTP-GDP exchange factor- hold on to GTP longer (in exchange for GDP) turn on signal

Question 32

What are the different types of cellular receptors?

Answer 32

Gated Ion channel- signal bind to receptor to allow ions go through channel enzyme linked receptors, G-protein linked receptors,- signal bind to receptor which will activate g protein, G protein eventually bind to enzyme and activate enzyme Enzyme-associated receptors Steroid receptors.

Question 33

Distinguish between Non-NMDA and NMDA receptor? What does one receptor have that other does not?

Answer 33

Non-NMDA- only has binding site for glutamate | NMDA has binding site for glycine and Glutamate (excitatory)

Question 34

Describe G protein-linked receptors. | What are the three components of G-protein receptor that automatically turn off?

Answer 34

G protein receptors are: -largest family of cell surface receptors transmit signals via guanine nucleotide binding proteins functional diversity (receptor for neurotransmitter, hormone,, responsible for smell, taste and sight similar structure G proteins activate chain of events that alter concentration of one or more secondary messengers 3 components : receptor, G protein (alpha, gamma, beta), effector

Question 35

What happens when hormone signal binds to receptor in g protein?

Answer 35

Hormone bind to receptor, create confirmational change in receptor, activated receptor binds to G alpha subunit binding induces change in G alpha, bound GDP dissociates and becomes GTP; G alpha dissociates from Gbetagamma. Eventually, hormone unbinds from receptor, G alpha binds to effector, activating it Hydrolysis of GTP to GDP causes G alpha to dissociate from effector and reassociate with Gbeta gamma.

Question 36

What are secondary messengers?

Answer 36

small intracellular molecules that act on intracellular proteins. example: effector adenyl cyclase will activate secondary messenger cAMP. example of secondary messengers: 1. Cyclic AMP and Calcium (most common) 2. Cyclic GMP 3. Diacyl Glycerol 4. phosphoinotol diphosphate cycilc AMP activates protein kinase which ten activate and phosphorlates trancription regulator.

Question 37

Discuss the importance of Calcium.

Answer 37

Calcium is very important intracellular messenger necessary for variety of cellular responses concentration changes from nanomolar to micormolar depending on type of cell and cell state increase in Ca triggered by fertilization (increase in Ca from egg) Calcium seen in food like dairy products, green veggies, salmon, sardines

Question 38

Differentiate between Na+ driven Ca exchanger and Ca pump?

Answer 38

Na driven calcium exchanger does not need energy for sodium to enter inside cell in exchange for Ca out Calcium pump requires ATP and phosphorylation of receptor to allow calcium to come out. calcium pump in ER, ca bind to molecules in cytoplasm and calcium actively transported to mitochondria (no need for ATP)

Question 39

What is relationship between calcium and vasopressin?

Answer 39

As you increase the concentration of vasopressin, the elevation of calcium gets lower (frequency of elevation shrinks)

Question 40

What are the calcium binding proteins and calcium sensor proteins? What are the EF hands?

Answer 40

Calcium binding proteins: troponin C and Calmodulin Calcium sensor proteins: s100B, GCAPS, Nuerocalcin EF hands- domain that binds calcium.

Question 41

What happens to K+ channels when G proteins dissociate from receptor?

Answer 41

When G protien (alpha, gamma, beta) dissociate from receptor, K+ channels close, and GTP goes to GDP, lose phosphate.

Question 42

How is Protein kinase C activated? How do DAG and IP3 play a role?

Answer 42

Signal molecule binds to receptor activate g protein G protein then activates Phospholipase C which produces inositol phospholipid (DAG And IP3) DAG binds to protein kinase C, while calcium also binds to pKC which activates it. Calcium came from phosphorylation of calcium channel by IP3 phosphorylating channel.

Question 43

What are two examples of enzyme coupled receptors?

Answer 43

1. A signal molecule can bind to 2 catalytic domains which can activate each other (receptor can be enzyme) 2. Signal molecule can bind to receptor that has an associated enzyme, which will be activated.

Question 44

What happens when you phosphorylate Bad protein? What happens to Bcl2?

Answer 44

When Bad phosphorylated it will release active form of Bc12 which promotes cell survival (prevents inhibition) Phosphorylated Bad becomes inactive

Question 45

What are examples of signaling proteins? | What unique structure does universal estrogen receptor have?

Answer 45

Signal for hormones: cortisol, estradiol, testosterones, thyroxine signal: vitamins: vitamin D3, retinoic acid estrogen receptor has zinc fingers that are used to grab promoter of DNA.

Question 46

Explain the role of Notch and Delta protein?

Answer 46

Notch begins in Golgi and transported to PM, where Notch binds to delta, cleaved twice and notch tail migrates to nucleus (total of 3 cleavage sites) where tail binds to protein and activates transcription of genes.

Question 47

Differentiate between how the presence or absence affects transcription.

Answer 47

Absence of ethylene- ethylene receptor will be active, protein kinase active which leads to degradation of transcription regulator and ethylene responsive genes OFF. Presence of ethylene- ethylene receptor is inactive, protein kinase inactive, which will activate transcription regulator and turn on ethylene responsive genes.