Lectures 15 and 16: Cell Communication

Question 1

3 types of cell communication

Answer 1

1. Direct contact signaling
2. Local signaling
3. Long distance signaling

Question 2

types of direct contact signaling

Answer 2

cell junctions and cell-cell contact

Question 3

types of local signaling

Answer 3

autocrine, paracrine, synaptic

Question 4

long distance signaling types

Answer 4

hormonal

Question 5

In animal cells, direct contact communication of cell junctions occurs through

Answer 5

gap junctions

Question 6

In cell junctions, direct contact in plant cells occurs via

Answer 6

plasmodesmata

Question 7

what ensures that only the same types of cells mate with each other?

Answer 7

the unique matching between mating factor and receptor

Question 8

what are the three major steps of a signal transduction pathway?

Answer 8

signal reception, signal transduction, and cellular response

Question 9

how can cells communicate by direct contact?

Answer 9

1. With cell junctions; also plasmodesmata (allow molecules to pass readily between adjacent cells without crossing plasma membranes)
2. With cell surface molecules (cell-surface molecules on adjacent cells interact with each other, resulting in a signal passing between the cells)

Question 10

paracrine signaling

Answer 10

A signaling cell acts on nearby target cells by secreting molecules of a local regulator (a growth factor, for example).—that signal affects itself

Question 11

synaptic signaling

Answer 11

• an electrical signal along a nerve cell triggers the secretion of neurotransmitter molecules
• molecules act as chemical signals, diffusing across the synapse ( the narrow space between cells) triggering a response in the target cell
• in the nervous system

Question 12

what do both animals and plants use for long-distance signaling

Answer 12

hormones

Question 13

endocrine signaling

Answer 13

specialized cells (endocrine cells) release hormones, which travel through the circulatory sys-tem (via bloodstream) to other parts of the body, where they reach target cells that can recognize and respond to them

Question 14

signal transduction

Answer 14

series of steps by which a cell converts a signal into a response

Question 15

signal reception (step 1)

Answer 15

target cell’s detection of a signaling molecule coming from outside the cell (when molecule binds to receptor protein on target cell)

Question 16

signal transduction (step 2)

Answer 16

• transduction stage (changes the receptor protein in some way) converts the signal to a form that can bring about a specific cellular response
• mostly occurs in a series of relay molecules

Question 17

cellular response (step 3)

Answer 17

-The transduced signal finally triggers a specific cellular response
- cell signaling process helps ensure that crucial activities occur in the right cells, at the right time, and in proper coordination with the activities of other cells of the organism

Question 18

ligand

Answer 18

• A molecule that binds specifically to another molecule, usually a larger one
• signaling molecule

Question 19

types of ligands

Answer 19

growth factors, hormones, neurotransmitters

Question 20

types of receptors

Answer 20

G protein linked receptors, tyrosine kinases, ion channel receptors, intracellular receptors

Question 21

G protein-coupled receptor

Answer 21

a cell-surface transmembrane receptor that works with the help of a G protein

Question 22

G protein

Answer 22

a protein that binds the energy-rich molecule GTP

Question 23

pathway of GPCR (steps)

Answer 23

1. protein is inactive when GDP is bound to it (on or off)
2. when signaling molecule binds to receptor –> receptor then binds to inactive G protein –> switches to GTP (now activated)
3. activated protein dissociates from receptor and binds to enzyme triggering next step leading to cellular response
4. G protein returns to inactive state and can be reused

Question 24

G-proteins function

Answer 24

like an on and off switch (on and off signaling)

Question 25

GTP is mostly found in the

Answer 25

cytosol

Question 26

pathway of tyrosine kinase receptors (RTKs)

Answer 26

1. receptors exist as individual molecules with binding site on the extracellular side of membrane (alpha helix) tail inside contains multiple tyrosine
2. binding of signaling molecule causes individual monomers to associate closely (form dimer)
3. dimerization activates the kinase region of each monomer – phosphate groups are added
4. activated receptor is recognized by specific relay proteins (specific molecules for specific tyrosine) –> triggers cellular response

Question 27

what is a key difference between RTK’s and GPCR’s?

Answer 27

with a single ligand-binding, RTKs trigger many pathways

Question 28

dimerization

Answer 28

bring together two receptor-hormone complexes

Question 29

ligand-gated ion channel

Answer 29

1. channel is closed when there is no signaling molecule
2. channel opens when molecule binds to site –> ions can flow through
3. when ligand dissociates channel closes

Question 30

intracellular receptor pathway

Answer 30

1. steroid hormone passes through the membrane
2. hormone binds to receptor protein in cytoplasm
3. hormon-receptor complex enters the nucleus and binds to specific genes
4. bound protein acts as a transcription factor stimulating transcription of the gene into mRNA
5. mRNA is translated into specific protein

Question 31

Cyclical AMP (cAMP)

Answer 31

important second messenger in G-protein

Question 32

second messengers

Answer 32

small molecules or ions that relay signals received by cell-surface receptors to effector proteins

Question 33

why do cells with the same receptor proteins have different pathways?

Answer 33

because they contain different proteins therefore the proteins will react differently