Cell biology - theme 2

Question 1

endocrine signalling

Answer 1

public
metabolism
hormones produced and secreted by endocrine organs into blood
protein hormones by receptors on membrane
steroid hormones on intracellular receptors

Question 2

paracrine signalling

Answer 2

less public
development, wound healing, inflammation
cytokines and growth factors act on receptors on plasma membrane and diffuse through extracellular fluid

Question 3

neuronal signalling

Answer 3

private

electrical signals via axons trigger extracellular chemical signals to target cell

Question 4

contact dependent signalling

Answer 4

development and immune response
membrane or matrix bound molecules are the signalling molecules and bind to receptor on target cell by direct physical contact

Question 5

oscillation

Answer 5

negative feedback, inhibitory product

Question 6

switching

Answer 6

positive feedback

Question 7

3 types of extracellular receptors

Answer 7

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

Question 8

mRNA

Answer 8

code for proteins

Question 9

rRNA

Answer 9

ribosomal structure and catalytic activity

Question 10

miRNA

Answer 10

regulate gene expression

Question 11

tRNA

Answer 11

adaptor linking amino acids to mRNA

Question 12

snRNA

Answer 12

join exons together after introns are spliced out

Question 13

start codon

Answer 13

AUG (methionine)

Question 14

untranslated region of RNA

Answer 14

5’ UTR is the sequences of bases from 5’ to AUG

Question 15

stop codon

Answer 15

UAG, UGA, UAA

Question 16

what tags unneeded proteins for degradation

Answer 16

ubiquitin proteins

e.g. degrade misfolded proteins

Question 17

how does cortisol work

Answer 17

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)

Question 18

homeotic genes

Answer 18

encode transcription factor, supply positional information

Question 19

cell communication

Answer 19

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

Question 20

rapid responses

Answer 20

change activity of already present proteins in cell e.g. muscle contraction

Question 21

slow responses

Answer 21

require changes in gene expression and protein synthesis e.g. cell division

Question 22

wobble

Answer 22

tRNA anticodon only accurately bind with first two bases of mRNA so fewer tRNAs than codons