T15 - HOW DO CELLS COMMUNICATE?

Question 1

signal transduction pathway

Answer 1

1. signal reception
2. signal transduction
3. cellular response

this allows signalling/chemical secretion to initiate a signal and cause the necessary response

Question 2

2 types of signallings

Answer 2

paracine signalling
- type of local signallling in animals - using local regulators to influence cells

synaptic signallings
- used in nervous system to transmit electrical signall - local

Question 3

signal reception

Answer 3

production of a signal
- signal produced from outside cell where it binds to receptors - this receptor is specific so signal only received by target cell
- signal molecule acts as a ligand to bind another molecule - activating the receptor

Question 4

signal transduction

Answer 4

perception - receptor kinases
- outside the cells, can phosphorylate proteins when activated, leading to activation or amplification

• this also allows for the control of this step

Question 5

cellular response

Answer 5

transudce signal triggers specific cellular response, either nuclear or cytoplasmic
- this canbe a response to amplify or regulate gene expression or protein synthesis
- allows transcription factor to bind to DNA sequence
- coordinate gene activity

Question 6

example is yeast cells

Answer 6

yeast cells identify their sexual mate by chemical signalling
- mating type a and alpha
-each secrete their factor (a secrets factor a and alpha secrets factor alpha)
- each cell has partners receptor on it so factor can bind and activate receptor to induce change in cells to lead to fusion
- a has alpha receptor and alpha has a receptor

Question 7

Stems

Answer 7

main function - elongate and orient the shoot to maximise photosynthesis
consists of:
- alternating system of nodes - where leaves attached
- internodes - stem segments between the nodes
- axillary bud - found between the leaf and stem

Question 8

when growing the growth is concentrated at…

Answer 8

the apical bud - shoot tip- contains stem cells

Question 9

rhizomes

Answer 9

horizontal shoot that grown below the surface with vertical shoots emerging from axillary budss

Question 10

stolons

Answer 10

horizontal shoots that grow along the surfaces as runner which enable plants to asexually reproduce - plantlets grow from axillary buds on runners

Question 11

tubers

Answer 11

elarged ends of rhizomes or stolons specailsed for storing food - cluster of axillary buds

Question 12

primary growth of shoots

Answer 12

all biomass of primary shooot is first dervied from apical meristem - shoot tip
- cell elongation is due to lengthing of internode cells below shoot tip

Question 13

3 different types of meristems that give rise to mature primary tissues

Answer 13

protoderm
ground meristem
procambium

Question 14

what is primary growth triggered by?

Answer 14

triggered by the activation of axillaty buds using plant hormone - auxin
- the closer the axillary bud is to the active apical bud, the more inhibited it is
- apical bud is the most dominant

Question 15

why is cell communication important?

Answer 15

• allow for the exchange of information between cells
• very important for unicellular and multicellular organisms
• allow response to changes in internal or external environment - homeostasis

Question 16

growth of shoot

Answer 16

apical meristem contains stem cells to allow for growth - producing a phytomer intially
- as shoot grows , natural buldges/buds grow that will form leaves

Question 17

removing apex

Answer 17

if remove the apical/ape tip, the axillary meristems begin to branch and grow until one becomes dominant

Question 18

if remove apex but add auxin to cut stump

Answer 18

the apical dominance is still maintained, no branching
- this shows how auxin is produced at the apex to prevent branching

Question 19

long distance signalling

Answer 19

uses hormones to do this

Question 20

strigolactone

Answer 20

hormone in plants used in long-distance signalling
- chemical produced in roots that triggers germination of striga - moves up to the shoot via the xylem to the axillary buds
- many genes and enzymes needed to produce strigolactone

Question 21

mutants of plants

Answer 21

found to have normal auxin levels but they disrupt the gene involved in production of mobile signal
- have increaed branching

whilst the wild type inhibits branching and promotes growth of main shoot

Question 22

uses grafting to show the effect of mutants

Answer 22

connect root of one plant to the stem of another
- joining the root of wild type with shoot of mutant
they found that the shoot grew like the wild type - inhibting branching
- this shows that signal is produced from the root and travels to the shoot - strigolactone
mutants do not have strigolactone

Question 23

why is there a branching signal (strigolatone) produced?

Answer 23

to reduce unnecessary growth of branches so the important biomolecules/nutrients (DNA phosphates, nitrates) are used to grow the main shoot