Protein Signals and Receptors

Question 1

what are the three different methods of short distance cell communication?

Answer 1

local signalling
direct contact between neighboring cells (gap junctions)
secreted messenger molecules e.g. synapses

Question 2

what is an example of long-distance cell signalling?

Answer 2

hormones and the endocrine system

Question 3

where is long-distance signalling found?

Answer 3

in plants and animals

Question 4

what is autocrine signalling?

Answer 4

where the cell targets itself

Question 5

what is juxtracine signalling?

Answer 5

when the cells are directly connected to each other

Question 6

what is paracine signalling?

Answer 6

when cells target a nearby, non-connected cell

Question 7

what is endocrine signalling?

Answer 7

when cells target a distant cell via the bloodstream

Question 8

what are the 3 stages of signal transduction?

Answer 8

reception, transduction and response

Question 9

what is reception in signal transduction?

Answer 9

when the signalling molecule (ligand) bonds to a receptor protein on the plasma membrane of the cell.

Question 10

what is transduction in signal transduction?

Answer 10

when the message is communicated by a series of proteins (relay molecules) changing shape until a response

Question 11

what is response in signal transduction?

Answer 11

when the response is carried out by an effector protein

Question 12

what are examples of effector proteins?

Answer 12

metabolic enzymes
gene- regulatory proteins - long term, carefully controlled changes
cytoskeletal proteins - alters the cytoskeleton of proteins having long or short-term effects.

Question 13

what is a long-term effect of a cytoskeletal protein?

Answer 13

stem cell change

Question 14

what is the short-term effect of a cytoskeletal protein?

Answer 14

change in shape

Question 15

which molecule is commonly used in signalling molecules?

Answer 15

GTP - guanosine tri-phosphate

Question 16

what does protein phsophorylation do?

Answer 16

changes the structural conformation of the protein

Question 17

what are key amino acids to phosphorylation events?

Answer 17

serine, threonine, tyrosine and histidene (phosphate groups are generally added to these amino acids)

Question 18

what process is important in amplifying a signal?

Answer 18

phosphorylation

Question 19

what is an example of a phosphorylation cascade?

Answer 19

adrenaline/epinephrine during the fight/flight response.

Question 20

what are G-protein coupled receptors?

Answer 20

a diverse group of membrane receptors found only in eukaryotes

Question 21

what are G-proteins made from?

Answer 21

7 alpha-helices

Question 22

what do G-proteins have roles in?

Answer 22

light - cellular signals
molecules in food - taste
regulation of the immune system, blood pressure and heart rate

Question 23

what do G-proteins do?

Answer 23

carry information from the receptor to enzymes which can activate an intracellular signalling pathway.

Question 24

what are tyrosine kinase receptors? (RTKs)

Answer 24

receptor proteins that cross the membrane

Question 25

what do RTKs do?

Answer 25

bind to extracellular ligands on the outside of the cell which can cause an internal signalling cascade

Question 26

what are examples of ligands that bind to RTK?

Answer 26

EGF - epidermal groth factor

HGF- human growth factor

Question 27

what are RTKs made of ?

Answer 27

2 monomers that are activated by binding to ligands and join together

Question 28

what is needed for relay proteins to attach to activated RTKs?

Answer 28

all 6 tyrosine kinase bases inside the membrane to be phosphorylated

Question 29

what is signal trasnduction?

Answer 29

when a signal changes from one form to another

Question 30

can phosphorylation cascades activate transcription factors within the nucleus?

Answer 30

yes

Question 31

what are P2X receptors?

Answer 31

ATP gated channels

Question 32

what are ligand gated ion channels?

Answer 32

channels opened by ligand binding leading to an influx of ions in the cell which can cause signals and cellular responses.

Question 33

what are steroid hormone receptors?

Answer 33

intracellular receptors

Question 34

what are the characteristics of steroid hormone receptors?

Answer 34

normally hydrophobic, lipid soluble and can cross the membrane. e.g. oestrogen and testosterone

Question 35

what is the typical end result of hormone receptor binding?

Answer 35

something entering the nucleus giving control over gene expression

Question 36

where do steroid receptor proteins bind?

Answer 36

proteins inside the cell

Question 37

what is ‘cross-talk’ ?

Answer 37

the different pathways and responses resulting from the same inital ligand

Question 38

what are negative feedback loops?

Answer 38

the regulation of processes with the cell in response to external stimuli (homeostasis)

Question 39

what are positive feedback loops?

Answer 39

a reinforcing or amplificaiton of signals

Question 40

what is an example of a negative feedback loop?

Answer 40

lack operon

Question 41

what is an example of a feedback loop gone wrong?

Answer 41

HPV binding to p53 and inactivating it, resulting in warts, mutations and cancer risks

Question 42

what is an MAPK pathway?

Answer 42

when communication is started with RTK and the end goal is transcription

Question 43

what is the fastest way to stop a signalling pathway?

Answer 43

using endocytosis to remove a receptor from the plasma membrane