Cell Communication

Question 1

what is a signal transduction pathway?

Answer 1

a series of steps bu which a signal on a cells surface is converted to a cellular response

Question 2

what signalling occurs in the NS?

Answer 2

chemical signalling between adjacent neurones

Question 3

what are neural signals?

Answer 3

diffusing a short distance between neurone

Question 4

what are neuroendocrine signals?

Answer 4

signals released from neurons but act on distant cells

Question 5

what are pheromones?

Answer 5

chemicals released into the environment and act on a different individual

Question 6

what is the direct mode of signalling?

Answer 6

direct signals from a cell-cell or a cell-matrix

Question 7

what is the indirect mode of signalling?

Answer 7

secreted molecules

Question 8

what is endocrine signalling?

Answer 8

signalling molecules are hormones that are carried through the circulation to act on a target cell

Question 9

what is paracrine signalling?

Answer 9

signalling molecules released by one cell that acts upon neighbouring cells

Question 10

what kind of signalling molecules act in a paracrine fashion?

Answer 10

neurotransmitters

Question 11

what is autocrine signalling?

Answer 11

cells respond to signalling molecules that they themselves produce

Question 12

what do animal and plant cells have that aids chemical signalling?

Answer 12

junctions that directly connect the cytoplasm of adjacent cells

Question 13

what are local regulators?

Answer 13

messenger molecules that travel only short distances

Question 14

what is an example of long distance signalling?

Answer 14

plants and animals using horomones to communicate

Question 15

what are the three types of signalling molecules?

Answer 15

steroid hormones, nitric oxide and carbon monoxide and neurotransmitters

Question 16

how do steroid hormones communicate with a cell?

Answer 16

diffuse across plasma. membrane and bond to receptors in the cytoplasm or the nucleus

Question 17

where do steroid hormones come from?

Answer 17

all synthesised from cholesterol

Question 18

what are examples of steroid hormones?

Answer 18

sex steroids and corticosteroids

Question 19

compare thyroid hormone, vitamin D3 and retinoid acid

Answer 19

they all have different structures and functions yet share the same mechanism action

Question 20

what is a steroid receptor superfamily?

Answer 20

transcription factors either as activators or repressors of transcription

Question 21

what does NO do to a cell?

Answer 21

diffuses across the membrane and alters the activity of intracellular target enzymes

Question 22

what causes the effects of NO to be local?

Answer 22

it is extremely unstable

Question 23

what is an example of NO action?

Answer 23

signalling if the dilation of blood vessels

Question 24

how can steroid hormone action cause the production of a protein?

Answer 24

the hormone enters the cell and binds to a receptor in the cytosol, the complex then enters the nucleus and binds to a specific gene where it acts as a transcription factor causing mRNA to be produced and eventually a protein

Question 25

what are the three processes that cells receiving signals are said to go through?

Answer 25

reception, transduction and response

Question 26

what happens during reception?

Answer 26

signal molecule binds to a receptor protein causing a conformational change

Question 27

what are intracellular receptors?

Answer 27

receptors found in cytosol or the nucleus of target cells

Question 28

what are the three main types of receptor?

Answer 28

G protein receptors, tyrosine kinases and ion channels

Question 29

what does an active G protein look like?

Answer 29

GDP is bound to the G protein which causes it to be active

Question 30

what does a tyrosine kinase do?

Answer 30

attaches phosphates to tyrosine molecules

Question 31

what is a phoshphotransferase?

Answer 31

a type of enzyme that transfers phosphate groups to substrates

Question 32

what does ion channels do?

Answer 32

acts as a gate when a lingo binds this causes a change in shape allowing ions through

Question 33

what happens during transduction?

Answer 33

multiple steps occur that amplify the signal e.g. multistep pathways

Question 34

what do multistep pathways do?

Answer 34

provide more opportunities for coordination and regulation

Question 35

what occurs at each step of a single transduction pathway?

Answer 35

a conformational change

Question 36

what kind of enzyme causes dephosphorylation?

Answer 36

phosphotases

Question 37

how can signals be transmitted in a signal pathway?

Answer 37

via a cascade of phosphorylations

Question 38

what are second messengers?

Answer 38

small, non-protein water soluble molecules

Question 39

what is the first messenger?

Answer 39

the extracellular signal molecule that binds to the membrane

Question 40

what receptors do second messengers take part in?

Answer 40

G protein receptors and tyrosine kinases

Question 41

how is ATP converted to cAMP?

Answer 41

adenylyl cyclase is responsible for the conversion in response to an extracellular signal

Question 42

how does activation of a G protein lead to the activation of protein kinase A?

Answer 42

G protein activated which activates adenylyl cyclase which then converts ATP to cAMP and cAMP then activates protein kinase A

Question 43

what makes calcium an important second messenger?

Answer 43

because cells can regulate its concentration

Question 44

what two things does a pathway leading to the increase in calcium involve?

Answer 44

inositol triphosphate (IP3) and diacylglycerol (DAG) as second messengers

Question 45

what happens in response?

Answer 45

a signal transduction pathway leads to regulation of one or more cellular activities

Question 46

where can the response occur?

Answer 46

in the cytoplasm or the nucleus

Question 47

what is a common response to a signalling pathway?

Answer 47

the regulation of function of a transcription factor

Question 48

how does epinephrine lead to the production of glucose?

Answer 48

signalling pathway activates protein kinase A, which then activates glycogen phosphorylase, which then converts glycogen to glucose 1 phosphate

Question 49

what are the 4 aspects if fine tuning the response?

Answer 49

amplifying the signal, specificity of the response, overall efficiency of the response and termination of the signal

Question 50

what do scaffolding proteins do?

Answer 50

enhance the overall efficiency of the response

Question 51

what gives specificity of a response?

Answer 51

different kinds of cells have different collections of proteins

Question 52

what helps to coordinate signals?

Answer 52

pathway branching and cross talk

Question 53

what causes termination of a signal?

Answer 53

the signal molecule leaving the receptor which causes the receptor to revert to its inactive state