Cell biology - theme 2 Flashcards
endocrine signalling
public
metabolism
hormones produced and secreted by endocrine organs into blood
protein hormones by receptors on membrane
steroid hormones on intracellular receptors
paracrine signalling
less public
development, wound healing, inflammation
cytokines and growth factors act on receptors on plasma membrane and diffuse through extracellular fluid
neuronal signalling
private
electrical signals via axons trigger extracellular chemical signals to target cell
contact dependent signalling
development and immune response
membrane or matrix bound molecules are the signalling molecules and bind to receptor on target cell by direct physical contact
oscillation
negative feedback, inhibitory product
switching
positive feedback
3 types of extracellular receptors
ion-channel linked receptors
changes permeability of membrane to selected ions
e.g. excitable cells (neurons, muscle)
G-protein coupled receptors
activate G-proteins to turn on/ off enzymes or ion channels
in most cells
enzyme coupled receptors
act directly as an enzyme
in most cells
mRNA
code for proteins
rRNA
ribosomal structure and catalytic activity
miRNA
regulate gene expression
tRNA
adaptor linking amino acids to mRNA
snRNA
join exons together after introns are spliced out
start codon
AUG (methionine)
untranslated region of RNA
5’ UTR is the sequences of bases from 5’ to AUG
stop codon
UAG, UGA, UAA
what tags unneeded proteins for degradation
ubiquitin proteins
e.g. degrade misfolded proteins
how does cortisol work
from adrenal glands in response to prolonged stress and starvation
cortisol binds to receptor to create transcription factor
activates gene transcription
response to increase amino acid -> glucose
(increase gluconeogenesis, lipolysis, amino acid breakdown)
homeotic genes
encode transcription factor, supply positional information
cell communication
1) signalling by many extracellular signals from extracellular signalling molecules
2) selective signal receptor on target cell
3) signal transduction - conversion of signal from one form to another
4) intracellular signalling molecules
5) molecular change e.g. gene transcription/ protein function
6) alteration in cell behaviour
rapid responses
change activity of already present proteins in cell e.g. muscle contraction
slow responses
require changes in gene expression and protein synthesis e.g. cell division
wobble
tRNA anticodon only accurately bind with first two bases of mRNA so fewer tRNAs than codons
