Cell Communication (Week 1)

Question 1

Explain how the specialized form of short-range signaling is carried out between neuron to neuron and neuron to muscle cell.

Answer 1

• Neurons release signaling molecules known as neurotransmitters by diffusing across the synapse (gap). The response is usually a further transmission of a nerve impulse and another release of neurotransmitters.
• Muscles cells will usually respond from the short range signal by contract rather than relaying as stated in previous bullet.

Question 2

Autocrine Signaling

Answer 2

Signaling and responding cell are the same.

Question 3

What is the difference between polar and nonpolar signaling molecules released by the signaling cell in regards to the responding cell’s membrane?

Answer 3

Polar signaling molecules cannot cross the plasma membrane of the responding cell and usually bind to protein receptors instead. Nonpolar signaling molecules may cross the responding cell membrane and bind to protein receptors inside the responding cell.

Question 4

What are the steps in cell signaling?

Answer 4

1. receptor activation
2. signal transduction
3. response
4. termination

Question 5

What is signal transduction in terms of cell communication?

Answer 5

Signal transduction is a chain reaction or a cascade of biochemical events set of by the binding and activation of the receptor. A low signal can have a large affect on the cell since the signal is amplified at each step of the pathway.

Question 6

Endocrine Signaling

Answer 6

Signaling via molecules that travel through the blood stream.

Question 7

Paracrine Signaling

Answer 7

Signaling molecule movement between two cells by diffusion. The distance is about 20 cell diameters or a few hundred micrometers.

Question 8

What is a growth factor?

Answer 8

a type of signaling molecule that cause the cell to grow, divide, or differentiate.

Question 9

What are glial cells?

Answer 9

Glial cells are supporting cells found in the central nervous system that help nourish and insulate the neurons.

Question 10

What happens when the notch receptor is activated by the delta protein?

Answer 10

The undifferentiated cell becomes a glial cell and not a neuron.

Question 11

What part of the receptor protein does the signaling molecule bind to?

Answer 11

The ligand-binding site. The bond is non-covalent.

Question 12

What is special about steroids in regards to the cell membrane? What is special about the shape of a steroid?

Answer 12

Steroids are hydrophobic which allows them to pass through the hydrophobic center of the cell membrane layer and into the target cell. The steroid is known to have four connected carbon rings.

Question 13

What does it mean when a receptor “couples to” something?

Answer 13

It means it associates with it. It basically means combine.

Question 14

What is a kinase?

Answer 14

An enzyme that catalyzes the transfer of a ATP to a substrate. A substrate is a substance on which an enzyme acts.

Question 15

What happens when a protein is phosphorylated by a kinase?

Answer 15

It becomes active and is said to be “switched on”.

Question 16

What does a phosphatase do?

Answer 16

It dephosphorylates a protein which removes the phosphate group added from ATP which is said to have “switched the protein off”.

Question 17

What exactly is Pi?

Answer 17

Pi is used for to denote the inorganic phosphate group that is either removed or added to form ADP or ATP respectively.

Question 18

What are the two groups of ion channels?

Answer 18

voltage-gated ion channels and ligand-gated ion channels.

Question 19

What are the 2 characteristics of a G-protein coupled receptor?

Answer 19

1. single polypeptide with 7 transmembrane proteins

2. It binds to a G-protein when activated

Question 20

What happens to the G-protein when bound to GTP or GDP?

Answer 20

GTP turns the G-protein on and GDP turns the G-protein off.

Question 21

What are the three subgroups that make up the G-protein and what happen when GDP is switched with GTP?

Answer 21

The three subgroups that make up the G-protein are alpha, beta, and gamma. When GDP is switched with GTP the protein is activated and the alpha group breaks off from the beta and gamma subgroups to aid in the next step of the transduction pathway.

Question 22

What happens in the next step when the alpha subunit with the attached GTP component is detached from the beta and gamma subunits in the transduction pathway from the initial activation by adrenaline. What is significant in regards to the signal in this process?

Answer 22

The activated alpha subunit attaches to adenylyl cyclase which then converts ATP into cAMP. cAMP is known as the second messenger and many cAMP molecules are made which results in the amplification of the signal.

Question 23

Where does cAMP go after being synthesized by adenylyl cyclase?

Answer 23

cAMP now goes and binds with protein kinase A (PKA).

Question 24

What happens to protein kinase A after being activated by cAMP? What is significant in regards to the signal in this process?

Answer 24

PKA phosphorylates multiple target proteins which basically means that it turns them on. The signal is amplified again in this step.

Question 25

What does activated PKA do in terms of the heart?

Answer 25

it allows calcium channels to open which results in short intervals between muscle contractions which basically is an increase in heart rate.

Question 26

What is binding affinity and why is it important in cell comunication?

Answer 26

Binding affinity is a property that refers to tightness of a bond. This is important because the strength of the bond determines the length of time the signaling molecule is bound to a receptor.

Question 27

What does platelet-derived growth factor (PDGF) after you cut your finger?

Answer 27

It binds to receptor kinases at the surface of cells near the wound after being released from platelets and instruct the cell to grow in order to repair the wound.

Question 28

What is dimerization? Why is it important for a receptor kinase?

Answer 28

The partnering of two similar or identical molecules. It allows the pair of receptor kinases to phosphorylate each other.

Question 29

What is different about the RAS G-protein in terms of structure?

Answer 29

It is a single subunit instead of three subunits.

Question 30

What are the three general features shared by complex multicellular organisms?

Answer 30

1. they have tightly developed molecular mechanisms for adhesion. 2. they display specialized structures for cell communication. 3. they display complex patterns of cell and tissue differentiation guided by regulatory genes.

Question 31

What is the key functional challenge of complex multicellularity?

Answer 31

the challenge is transporting food, oxygen and molecular signals rapidly across large distances within the body.

Question 32

What is bulk flow?

Answer 32

Bulk flow is any means by which molecules move through organisms at rates beyond those possible by diffusion across a concentration gradient

Question 33

What are gap junctions?

Answer 33

protein channels that allow ions and signaling molecules to move from one cell to another.

Question 34

What is the importance of cell junctions?

Answer 34

They allow for the connection of tissue.

Question 35

What is the extracellular matrix?

Answer 35

meshwork of proteins and polysaccharides outside of the cell.

Question 36

What are the two main layers of the skin and what are there functions?

Answer 36

The epidermis and the dermis. The epidermis is a water-resistant protective barrier while the dermis is its underlying support by transporting nutrients and providing a cushion surrounding the body.

Question 37

What do microtubules and microfilaments provide for the cell?

Answer 37

They provide structural support and shape as well as movement of substances within the cell.

Question 38

What is a microtubule?

Answer 38

a hollow tub formed from tubulin dimers known as alpha-tubulin and beta-tubulin.

Question 39

What is a microfilament?

Answer 39

a double helix of actin monomers. They are important for maintaining the shape of the cell such as the biconcave shape of the blood cell.

Question 40

What is are intermediate filaments and what kind of cell are they found in?

Answer 40

strong fibers of intermediate filament protein subunits. They are found in animal cells.

Question 41

What are the two motor proteins that associate with the microtubule track and in which way do they transport cargo?

Answer 41

Kinesin and dynein are the two motor proteins. Kinesin transports cargo toward the plus end of the microtubules near the periphery of the cell and dynein transports cargo toward the minus end located at the centrosome toward the interior of the cell.

Question 42

What is myosin and how is it similar to the kinesin and dynein interaction with the microtubule track?

Answer 42

Myosin is the motor protein for microfilaments. It allows for the transportation of cellular cargo like how the motor protein kinesin and dynein do for the microtubule. Microfilaments are also responsible for the shape of the cell. For example, muscle contraction depends on the interaction of myosin with microfilaments which cause the cell muscle cells to change shape by making them contract.

Question 43

What are integrins?

Answer 43

They are cell adhesion molecules that allow cells to attach themselves to the extracellular matrix.