Cell signalling

Question 1

How did plants and animals evolve multicellularity and cell communication mechanisms?

Answer 1

Independently, each starting from a different unicellular eukaryote, which in turn evolved from a common unicellular eukaryotic ancestor.

Question 2

Differences between cell signalling mechanisms between plants and animals

Answer 2

Animals - rely heavily on GPCRs and RTKs
Plants - rely mainly on enzyme-coupled receptors of the receptor serine/threonine kinase type, especially ones with extracellular leucine-rich repeats

Question 3

Give 2 examples of hormones, or growth regulators, that help coordinate plant development

Answer 3

1. Ethylene

2. Auxin

Question 4

How does ethylene help coordinate plant development?

Answer 4

Acts through intracellular receptors to stop the degradation of specific nuclear transcription regulators (auxin also does this), which can then activate the transcription of ethylene-responsive genes.

Question 5

Why is auxin signalling unusual?

Answer 5

Has its own highly regulated transport system. Dynamic positioning of plasma-membrane-bound auxin transporters controls the direction auxin flow and so direction of plant growth.

Question 6

Other than hormones/growth regulators, what else has an important role in regulating plant development?

Answer 6

Light

Question 7

How are light responses mediated? Give 3 examples

Answer 7

By a variety of light sensitive photoproteins, including phytochromes, cryptochromes and phototropin.

Question 8

What kind of light are phytochromes responsive/sensitive to?

Answer 8

Red

Question 9

What kind of light are cryptochromes and phototropin responsive/sensitive to?

Answer 9

Blue