21 Cell Signalling

Question 1

what is cell signalling/ purpose?

Answer 1

• one cell produces chemical signal to be recognised by another cell using receptors - to produce a specific response
• mating among single celled. organisms - to detect cells of opposite sex
• multicellular organisms: coordinate maintenance - homeostasis, replacement of cells etc. (cell death signalling - cancer)

Question 2

signalling in energy homeostasis - insulin regulation

Answer 2

food intake

• detected as rise in blood glucose + amino acids
• pancreatic B cells recognise & secrete insulin (signal)
• acts on adipose, muscle, liver tissues
• take up glucose/amino acids (as lipids/glycogen)

Question 3

4 types of cell signalling

Answer 3

endocrine
uses hormones, long distance, slow signal, sent in blood, general broadcast but only picked up by cells w those receptors

(autocrine acts on themselves)

paracrine
localised, fast signal, local diffusion to neighbouring cells.

neuronal
how neurone communicate, use neurotransmitters to cross synapses, electrical impulse down them, specific communication between target and signalling cell, travel long distances

contact dependant
short range signal, cells must be in direct contact to communicate, no chemical transmitters just direct contact of signalling/receptor molecules on membrane surface

Question 4

Signal molecules & their actions

Answer 4

delta notch
Nitrate oxide
insulin

Question 5

Delta (signal) & Notch (receptor) signalling system

Answer 5

• in nervous system, use contact dependant signalling

-

Question 6

what is signal transduction?

Answer 6

conversion of one signal type to another in multicelluar organisms

Question 7

extracellular vs intracellular signalling molecules

Answer 7

extracellular - between cells signals

intracellular - signals between components within a cell as a result of external signals

Question 8

local mediators/ paracrine signalling

Answer 8

local cell signal molecules - not like hormones where signal travels in blood, local diffusion to neighbouring cells.

Question 9

types of cell membrane receptors

Answer 9

ion transmitter Chanel coupled receptors: transmitter gated ion channels

G protein (extracellular signal receptor) coupled receptors: G protein activates internal production of enzyme to make second messenger (intercellular) molecules
e.g smells, hormones, local signals, light

enzyme coupled receptors: receptor site with active enzyme to alter molecule?

Question 10

2 methods of protein conformational switches

Answer 10

conformational switch occurs in cell in response to signal (reversible)

through phosphorylation - ATP - ADP
through GTP binding - GTP - GDP

Question 11

ion transmitter Chanel coupled receptors purpose/process

Answer 11

receptor on cell surface picks up signal, triggers ion change to open = desired effect e.g. lowered potential difference (charge) = less reactive cell
reversible/temporary reaction, reset = beta + gamma subunits recombine, closes ion channel
e.g. application: regulating cardiac pacing from vagus nerve

Question 12

Cyclic AMP (cAMp-a)

Answer 12

second messenger (inracellular signal) activates Kinase (ATP phosphorylation) to realise energy from cell