Biosignalling

Question 1

What do extracellular signalling molecules bind to in the cell surface membrane?

Answer 1

protein receptors

Question 2

What happens when extracellular signalling molecules bind to protein receptors in the cell surface membrane?

Answer 2

a cascade of reactions inside the cell is triggered

Question 3

What are protein receptors in the cell membrane specific to?

Answer 3

extracellular signalling molecules

Question 4

How can a large intracellular response be created from a single protein receptor?

Answer 4

cascades can amplify the signal they receive, very few molecules can lead to a large intracellular response

Question 5

What must cells be able to do once the signal concentration falls?

Answer 5

switch off the response

Question 6

what are the 4 types of inter cellular signalling?

Answer 6

endocrine, paracrine, neuronal, contact dependent

Question 7

How does endocrine inter cellular signalling work?

Answer 7

the signalling molecules from one cell/tissue travel to other cells/tissues via the blood stream

Question 8

How does pancrine intercellular signalling work?

Answer 8

signalling molecules from one cell act on the cells in the immediate surrounding area

Question 9

How does neuronal intercellular signalling work?

Answer 9

signalling molecules are released from the end plate of a neuronal cell and travel across a synapse to the receptors on the target cell

Question 10

How does contact dependent intercellular signalling work?

Answer 10

siganlling molecules are expressed on the cell surface of one cell and bind to the receptors of another cell when the two come into contact

Question 11

What is the cell response the sum of?

Answer 11

all the signals it receives

Question 12

What else determines a cells response aside from the signal strength?

Answer 12

the cell type

Question 13

Do different cells have the same/similar receptors for the same signal molecules?

Answer 13

yes

Question 14

What differs between cell types in terms of their response to signaling?

Answer 14

they have different intracellular cascades with different effector proteins

Question 15

How do different intracellular cascades and effector proteins affect the cells response to signal proteins?

Answer 15

they can have different responses to the signal protein

Question 16

How does acetylcholine affect heart muscle cells, salivary gland cells and skeletal muscle cells when it binds to the receptor molecule?

Answer 16

heart muscle cell: decreased rate and force of contraction
salivary gland cell: secretion of saliva
Skeletal muscle cell: contraction

Question 17

What are the two speeds of cell response to signal proteins?

Answer 17

fast or slow

Question 18

What do fast cell responses involve?

Answer 18

altering protein function within the cell

Question 19

What does altered protein function within the cell after fast response to signal proteins lead to?

Answer 19

altered cytoplasmic behavior and altered cell response

Question 20

How quickly does a fast cell response happen?

Answer 20

within milliseconds to a few minutes of receiving the signalling molecule

Question 21

What do slow cell responses involve?

Answer 21

altering gene expression leading to the increase/decrease of protein synthesis or synthesising new proteins

Question 22

how is gene expression altered by signalling proteins?

Answer 22

increasing or changing the signals to the DNA for protein synthesis

Question 23

How does the change in amount or type of proteins synthesized affect the cell?

Answer 23

alters cytoplasmic behavior and alters cell response

Question 24

how quickly does a slow cell response to signal molecules happen?

Answer 24

minutes to hours

Question 25

Where can receptors be located?

Answer 25

on the cell surface membrane or intracellular

Question 26

What type of signalling molecules do intracellular receptors require?

Answer 26

hydrophillic ones that can enter the cell

Question 27

What receptors can hydrophobic signalling molecules bind to?

Answer 27

only cell surface receptors

Question 28

What are the 3 types of cell surface receptors?

Answer 28

ion-channel coupled receptors, G protein couple receptors (GPCRs), enzyme coupled receptors

Question 29

Give 2 examples of electronically excitable cells

Answer 29

muscle and nervous system cells

Question 30

In what type of cells are ion-channel coupled receptors located?

Answer 30

electrically excitable cells

Question 31

What do cell surface receptors in electrically excitable cells convert?

Answer 31

chemical signals to electrical ones

Question 32

What happens when the signalling molecule binds to the ion channel?

Answer 32

it opens allowing ions across the plasma membrane

Question 33

What are ions?

Answer 33

charged molecules (eg Cl-, K+)

Question 34

What does the movement of ions across the plasma membrane do to the membrane?

Answer 34

changes membrane potential of the cell and produces and electric current

Question 35

What body function are ion-channel coupled receptors responsible for?

Answer 35

rapid transmission of signals across synapses in the nervous system

Question 36

What are G proteins?

Answer 36

a class of proteins that sit in the plasma membrane and amplify the signal from receptor molecules

Question 37

What are G proteins linked to?

Answer 37

cell surface receptors

Question 38

What do the cell surface receptors linked to G proteins do when activated by a signalling molecule?

Answer 38

activate G proteins

Question 39

What do G proteins do once activated by linked cell surface receptors?

Answer 39

activate many enzyme molecules, amplifying the signal by producing large quantities of secondary messenger molecules

Question 40

Give and example of where GPCR is used?

Answer 40

adrenaline moved through GPCR to stimulate glycogen breakdown in skeletal muscle

Question 41

What does adrenaline bind to when using GPCR?

Answer 41

beta adrenergic GPCR in the plasma membrane

Question 42

What subunit of the G protein activates adenyl cyclase?

Answer 42

alpha subunit

Question 43

What is adenyl cyclase?

Answer 43

an enzyme that produces cyclic AMP (cAMP) from ATP

Question 44

What does cyclic AMP activate during the GPCR response?

Answer 44

cAMP dependant protein kinase (PKA)

Question 45

What does PKA activate, once it has been activated by cyclic AMP, and how does it activate it?

Answer 45

phosphorylase kinase by adding a phosphate group to it from ATP

Question 46

What does active phosphorylase kinase activate and how does it do this?

Answer 46

glycogen phosphorylase by adding a phosphate group to it from ATP (phosphorylation)

Question 47

What does the activated glycogen phosphorylase catalyse at the end of the GPCR cascade?

Answer 47

glycogen breakdown

Question 48

What are receptor tyrosine kinases (RTKs)?

Answer 48

a large family of cell surface receptors that have intrinsic protein kinase activity

Question 49

What does the binding of a signalling molecule to RTKs induce?

Answer 49

formation of a dimer from receptors (joined molecules) which then activates intracellular proteins (protein kinase)

Question 50

What does the activation of the intracellular protein kinase domain do?

Answer 50

phosphorylates both the receptor (autophosphorylation) and other target proteins that are on the tyrosine residues

Question 51

Once the phosphorylation of receptors and target proteins has occurred in the RTK signalling response what happens to the signal?

Answer 51

it is relayed by activated signalling proteins in the cells interior

Question 52

What are examples of RTK receptors?

Answer 52

insulin receptors and epidermal growth factor receptors

Question 53

What are secondary receptors?

Answer 53

intracellular receptors that bind to molecules released by cell surface receptors

Question 54

What are the molecules that can often enter cells?

Answer 54

hormones

Question 55

What binds to intracellular signalling receptors?

Answer 55

signalling molecules that enter the cell

Question 56

How is a hormone typically carried to tissues?

Answer 56

via a serum binding protein which diffuses across the cell membrane

Question 57

Once in the cell what does the hormone bind to?

Answer 57

intracellular receptor in the cell nucleus

Question 58

What does the binding of the hormone to the intracellular receptor in the cell nucleus cause?

Answer 58

dimerization with other hormone receptor complexes

Question 59

What are specific regulatory regions in the DNA called?

Answer 59

hormone response elements (HREs)

Question 60

What are HREs adjacent to?

Answer 60

specific genes

Question 61

What does the dimerised intracellular hormone receptor attract?

Answer 61

coactivator/compressor protein(s) that regulate the transcription of the adjacent gene

Question 62

What does the increased/decreased mRNA production, as a result of coactivator/conmpressor proteins, alter?

Answer 62

the production of the corresponding protein which produces a cellular response