Signalling

Question 1

signalling: basic principles- transmembrane proteins, signal transduction

Answer 1

• binding of ligand to receptor protein in cell plasma membrane -> changes intracellular portion of receptor
• receptor: transmembrane proteins (parts both out of cell/ in cytoplasm)
• signal from ligand binding causes phosphorylation of proteins (change shape/ function)
• signal transduction (cascade of phosphorylation) causes one or more responses in cell, (including change in protein function/ gene transcription)

Question 2

ligand interaction: not lipid soluble

Answer 2

bind to receptors on surface of target cell

Question 3

ligand interaction: most not lipid soluble

Answer 3

bind to receptors on surface of target cell

Question 4

ligand interaction: lipid soluble

Answer 4

often bind to receptors inside target cell

Question 5

eg. adrenaline signalling

Answer 5

• fight/flight response

acute stress response:

• nausea, loss of appetite
• increase energy and agitation
• stimulated by epinephrine (adrenaline) from adrenal gland

Question 6

cAMP:

Answer 6

• cyclic adenosine monophosphate
• secondary messenger in cell
• activates kinase proteins which add phosphate group to enzyme -> breaks down glycogen into glucose for energy

Question 7

release glucose from liver cell: pathway

Answer 7

adrenalin detected by adrenergic receptor - G protein dissociates - cAMP activates - kinase - breaks down glycogen - glucose - energy

Question 8

list phases of cell signalling:

Answer 8

• reception
• transduction
• response

Question 9

reception:

Answer 9

ligand binds to receptor

Question 10

transduction:

Answer 10

receptor activates signal transduction molecule

- sometimes initiates signalling cascade

Question 11

response:

Answer 11

• eg. stimulates glycogen breakdown

Question 12

list types of receptors which bound to ligands:

Answer 12

• receptor tyrosine kinase
• G-protein coupled receptor
• ligand-gated ion channel

Question 13

receptor tyrosin kinase:

Answer 13

• paired receptor

- cytoplasmic portions cross phosphorylate at tyrosine residues

Question 14

G-protein coupled receptor:

Answer 14

• receptor coupled with G protein

- when activated activates adenylyl cyclase

Question 15

ligand-gated ion channels:

Answer 15

• open to allow ion flow across membrane

- direct response

Question 16

ion:

Answer 16

• charged atom/ molecule

- neither negative/positive charge can pass membrane

Question 17

mitochondria:

Answer 17

• produce ATP
• C6H12O6 + 6O2 –> 6CO2 + 6H2O
• 30-32 ATP per molecule glucose
• opposite of photosynthesis

Question 18

major reaction pathways of ATP production:

Answer 18

• glycolysis
• Krebs cycle (citric acid)
• electron transport phosphorylation (chemiosmosis)

Question 19

aerobic respiration:

Answer 19

• production of ATP dependent on oxygen

Question 20

anaerobic fermentation:

Answer 20

• oxygen limited
• glycotic products metabolised this way
• independent of mitochondria

Question 21

phosphorylated:

Answer 21

• when signalling receptors activated, cytoplasmic proteins are phosphorylated
• phosphate group added to molecule
• usually donated from ATP
• protein kinase transfer phosphate

Question 22

significance: phosphorylation

Answer 22

• frequently changes proteins confirmation and surface charge

Question 23

de-phosphorylation:

Answer 23

protein phosphotases removes phosphate from protein

Question 24

significance: phosphorylation/ de-phosphorylation

Answer 24

• act as molecular switch, turning protein on and off

Question 25

transduction:

Answer 25

- cascade of molecular interactions relay signals from receptors to target molecules in cell

Question 26

significance: signal transduction

Answer 26

- multiple steps - can amplify signal - more opportunity for coordination and regulation of cellular response

Question 27

response to a signal:

Answer 27

- regulation of one or more cellular activities

Question 28

cytoplasmic: and eg

Answer 28

output response in cytoplasm | - eg. change in enzyme's activity

Question 29

nuclear: and eg.

Answer 29

output response in nucleus, effecting change in gene expression - final activated molecule may function as transcription factor (binds to DNA, blocks/ enhances transcription of gene)

Question 30

list two ways cells direct changes in proteins via signal pathway:

Answer 30

- phosphorylation | - gene regulation

Question 31

faster response:

Answer 31

- phosphorylation quickly alters protein activity (activate/deactivate) but only affect existing proteins in cytoplasm

Question 32

slower response:

Answer 32

- gene regulation can lead to production of new proteins/ change protein conc. in cell - if gene expression is down-regulated, takes some time for cell concentration of gene product (protein) to deplete

Question 33

insuline binding results:

Answer 33

- several responses - most anabolic - stimulates synthesis and storage of carbohydrates, proteins, fatty acids