Unit 1 - Signal Transduction Flashcards Preview

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Flashcards in Unit 1 - Signal Transduction Deck (117)
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1

Molecular

activation of enzyme, generation/synthesis of metabolite and its degradation

2

cellular

number of mitochondria regulated in a cell may divide, split, fuse

3

tissue/organ

no of cells or cell types are tightly regulated

4

4 levels of regulation in living organism

molecular

cellular

tissue/organ

organism (neuro-endocrine)

5

main mechanims of integration of the levels of regulation

HPA axis

6

what is the target of regulation

7

definition of signal transduction

process linking the signal-activated receptor and the biological response

there is a common logic in the structure of signal transducers and in the mode of their function

 

8

how is regulation initiated and and how does it flow

initiated by the signal (information) reaching the cell or formed within the cell

 

9

EC signal molecule → receptor protein → IC signalling proteins → target proteins

10

what can a signal be, based on their origin

from environment - pin, temp, light, smell

from organism - hormones, cytokines, metabolites

from within the same cell - DNA damage, ROS

11

what can a signal be if chemical

  • proteins - GH
  • peptides - insulin, neuropeptides
  • AAs, derivatives - thyroxine, dopamine, epinephrine
  • lipids - PGs, platelet activating factor
  • ions - Ca2+, Cl-
  • nucleotides - adenosines with specialised receptors on their surface
  • gases - nitric oxide (produced by endothelial cells – trigger smooth muscle relaxation and vasodilation)

12

types of signal transmission

13

what is the significance of ligand binding

specificity

amplification

co-ordination of response - the same receptor may be present on a number of cells

cell specific response - by regulating the number and function of receptors

14

example of disease that involves a cell-specific response

type 2 diabetes

autoinhibitory receptors are present on cells become inactivated and unresponsive

15

types of receptors

cell surface/transmembrane receptors

nuclear receptors

cytosolic receptors

16

receptors for what hormone are present on a wide variety of cells

cortisol

17

amplification system

Uniform response of cell

e.g. If a cell triggers lipid degradation, whole lipid synthesis across the cell has to shut down and lipid degradation must occur

Net 0 effect - what 1 process achieves, the other will undo

18

allosteric regulation

19

interconversion cycle

NOTE: enzyme specific - some are active phosphorylated, some are active dephosphorylated

20

Akt/Protein Kinase P interconversion cycle - 1st mechanism

inactive Akt → Akt by 2 mechanisms:

FIRST

phosphorylated serine 473 interacts with the linker between the kinase and pH domains

21

2nd mechanism in Akt/protein kinase P interconversion cycle

phosphorylated serine 477 and threonine 479 result in the displacement of the pH domains

22

enzyme cascade

23

acceptors

all signal transduction pathways culminate to control of function of proteins (mostly enzymes, ion channels, transporters), which are involved directly in formation of biological response

24

2 categories of acceptors

control of protein amount

gene expression

protein degradation

protein stabilisation (tumour suppression gene P53)

control of existing proteins

without covalent modification of the protein (P) - Allosteric activator binds to an allosteric enzyme complex

with covalent modification of the protein - reversible and irreversible (cleavage of 3 forms of enzymes e.g. digestive enzymes involved in cleavage of trypsinogen to inter trypsin)

25

tumour suppression gene P53

regulated by protein stabilisation

26

mechanisms of hormonal regulation

27

4 types of membrane bound receptors

ion channel enclosing receptors

7 transmembrane domain receptors

1 hydrophobic domain receptors (R with enzyme activity, R with no enzyme activity)

28

ligands that activate membrane bound receptors

hydrophilic

29

signalling via ion channel-enclosing receptor example

nicotinic ACh receptor

30

structure of nicotinic ACh receptor

binding results in

pentamer (2 x α, β, γ,  δ)

subunits surround a central pore

2 Ach binding sites from the pore

their binding is co-operative and leads to channel opening

channel is selective for divalent cations (+ve) - Na+ and Ca2+

hyperpolarisation with AP triggered